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Abstract:
  Objective  The exterior wall is the main enclosure structure of light wood-framed buildings. Its hygrothermal performance has a great impact on the durability, safety, comfort and energy consumption of buildings. In order to explore the influence of outdoor environment, wall orientation, floor height and other factors on the hygrothermal performance of multi-storey light wood-framed walls in cold zone, this study conducted an experimental study on the hygrothermal performance of light wood-framed walls in a multi-storey mixed structure building in Tianjin of northern China.  Method  The study conducted a field monitoring investigation of multi-storey light wood-framed walls of a hybrid building in Tianjin from Jan. 1st to Dec. 31st, 2020. Temperature and relative humidity of the stud cavity in the test walls, moisture content of wood studs, et al were monitored continuously. The influences of outdoor temperature and humidity, wall orientation and floor height on hygrothermal performance of the wall were analyzed, and the condensation risk and mold growth risk inside the wall were assessed.  Result  The trends of temperature and relative humidity of the stud cavity were approximately consistent with that of the outdoor environment. The trends of moisture content of wood studs were approximately consistent with the equilibrium moisture content of the stud cavity. While the amplitudes of the temperature and relative humidity of the stud cavity and the moisture content of wood studs were smaller than that of the outdoor environment. Relative humidity of the stud cavity and moisture content of wood studs increased with a time lag under heavy precipitation in a short term. Solar radiation on walls varied with orientations, resulting in the temperature difference. Temperature of the stud cavity in the southern wall was the highest, followed by that of the western, eastern and northern walls, while the distribution of relative humidity was opposite. The relative humidity of the stud cavity in the northern wall was the highest, followed by that of the eastern, western and southern wall. It was shown that the moisture content of wood studs in the western wall was the highest due to the high initial moisture content, followed by that of the northern, eastern and southern wall. Except for the western wall, the distribution of the moisture content of wood studs was roughly consistent with that of relative humidity. Relative humidity and moisture content of the stud cavity on the 1st floor were generally higher with larger amplitudes than the other floors. And its temperature was relatively lower. From May to August, the temperature of walls in the 4th floor was the highest, followed by that of the 3rd and 2nd floor. The relative humidity and moisture content in walls of the 2nd floor were highest, followed by that of the 3rd and 4th floor.   Conclusion  Temperature and relative humidity of the stud cavity and moisture content of wood studs are directly affected by the outdoor climate conditions, while the hygrothermal conditions in the wall keep relatively stable. The outdoor vapor permeation is effectively retarded by the well-designed light wood-framed wall in cold zones. The cavities of multi-storey light wood-framed walls have no risk of condensation or mold growth in 2020.
Abstract:
  Objective  Surface fire is the most common type of forest fire, which directly affects vegetation regeneration and nutrient allocation and circulation of ecosystem. The common indexes reflecting forest fire behavior are fire spreading speed, calorific value per unit area, fire intensity and flame height. The fire behavior simulation based on the actual stand and site conditions can reveal the conditions of forest fire occurrence, effectively judge the possibility of crown fire occurrence, and provide a scientific basis for forest fire prevention and firefighting decision-making.  Method  Typical forest stands (Robinia pseudoacacia forest, Pinus tabuliformis forest and Platycladus orientalis forest) in Mentougou District of Beijing were selected as the survey objects. 5 sample plots were set for each stand, a total of 15 sample plots. Through field investigation, the data of fuel load (shrub fuel, herb fuel, 1 h fuel load, 10 h fuel load, 100 h fuel load), stand factors (height of the first living branch, height under dead branches, tree height, DBH, canopy density) and site factors (altitude, slope gradient, slope aspect, slope position) were obtained. The BehavePlus6 software was used to simulate the fire behavior indicators of different stand types under varied fuel conditions based on meteorological parameters and fuel parameters, they are the spreading speed of surface fire, the calorific value per unit area, the intensity of fire line and the length of flame. Principal component analysis was conducted with R language, and the potential effects of stand factors, site factors and fuel factors on fire behavior were discussed according to the contribution rate.  Result  The total fuel loads of Platycladus orientalis forest (POF), Robinia pseudoacacia forest (RPF) and Pinus tabuliformis forest (PTF) were respectively 15.35, 17.59, 15.28 t/ha, in which, the inflammable fuel loads (up-layer leaf, flammable herb, 1 h fuel) were respectively 4.55, 4.41, and 6.18 t/ha, accounting for 29.6%, 25.1% and 40.4% of the total fuel load of the stand, respectively. In the period of fire protection, the average wind speed was 2.2 m/s (corresponding to 7.92 km/h), the simulation result of surface fire rate of spread was PTF > POF > RPF, and the numerical values respectively were 11.5, 11.1, 8.0 m/min. The simulation results of fire heat per unit area were PTF > POF > RPF, and the numerical values were 23 091, 21 155, and 18 413 kJ/m2, respectively. The simulation result of fireline intensity was PTF > POF > RPF, and the numerical values were 4 426, 3 882, 2 468 kW/m. The flame height range of POF, RPF and PTF was respectively 0.89−3.40 m, 1.34−2.91 m, 1.78−3.88 m. Under the same conditions, the flame height was PTF > POF > RPF. According to the contribution rates, the principal component analysis results were different by stands. The first and second principal components in POF, RPF and PTF respectively were fuel material composition and stand factors, fuel material composition and fuel moisture content, stand factors and fuel moisture content.   Conclusion  (1) Flammable combustible material load is a key factor affecting forest fire behavior. (2) Fuel moisture rate plays a decisive role in the value of fire behavior indicators, and the critical value of fuel moisture rate affects the type of forest fire. Combustibles are flammable when dry, and surface fires with fast spread and high intensity are easy to occur in windy weather. (3) The continuity of combustibles is the key factor that determines the development of surface fire into crown fire. The flame height greater than the height under first living or dead branches is very likely to develop from surface fire to crown fire, and it is very difficult to put out. It is recommended to prune and mow regularly to clean up the combustibles under the forest and then reduce the fire risk.
Abstract:
  Objective  The mechanization level of seedling planting in China is relatively low. The seedling supporting mechanism is one of the key institutions in the seedling planting system of the seedling transplanter. The rack and pinion seedling supporting mechanism for the poplar seedling transplanter in China is developed to ensure the planting effect of the seedling transplanting equipment.   Method  Firstly, aiming at the transplanting operation of long rod seedlings, the physical characteristics of fast-growing poplar seedlings were analyzed, the variation range data of seedling length and ground diameter were obtained, a design scheme of rack and pinion seedling supporting mechanism was proposed, the relationship between planting performance and motion parameters of rack and pinion seedling supporting mechanism was analyzed, the initial position of seedling supporting frame was calculated, and the working stroke of seedling supporting was determined. The contact collision algorithm was used to calculate the meshing constraints and motion parameters of gear and rack. We used ADAMS simulation software to establish and simulate the multi stiffness contact dynamic model of the seedling supporting mechanism, explore the influence of the gear rack modulus on the seedling supporting effect, analyze the accuracy of the seedling supporting movement through the displacement and speed change curve of the mass center of the seedling supporting frame, and verify the transmission performance of the seedling supporting mechanism structure through the change of transmission gear speed and the change of gear rack meshing force.   Result  The module of gear and rack was 9, and the seedling raising effect was the best. At this time, the speed fluctuation of the center of mass of the seedling raising support frame in the forward direction was small, and the displacement change was stable. The displacement and time were approximately linear. The seedling raising process was close to uniform motion, and the speed was about 122 mm/s. The single working stroke of seedling supporting movement reached 599.9 mm, which met the design requirements of more than 568.4 mm. The power transmission of gears at all levels of seedling supporting mechanism was stable, the maximum contact force of tooth surface was 512.6 N, which was far less than the material strength, and there was no jumping and blocking.   Conclusion  The simulation results show that the rack and pinion seedling supporting mechanism can meet the seedling supporting motion requirements of poplar seedling planting, realize zero speed transplanting, ensure the verticality of seedling planting, and effectively improve the previous seedling supporting methods in the process of seedling planting. It has good motion stability, safety and efficiency, and has a certain guiding role for afforestation machinery and equipment.
Abstract:
  Objective  In recent years, urban green space is increasingly fragmented because of urbanization, which seriously threatens urban bird diversity. River ecological corridor plays an important role in the protection of urban bird habitats. However, the diversity of different ecological community of birds is influenced by environmental factors at multiple scales. The habitat pattern optimization and habitat construction of birds in urban ecological corridors for specific ecological community need the support of theoretical research urgently. Based on the analysis of bird species composition in Beijing Wenyu River ecological corridor in spring, we comprehensively analyzed the effects of environmental factors on bird species composition of different ecological communities at three scales of landscape pattern, habitat patch and micro-habitat, in order to understand the impact of environmental factors on bird habitat selection, and provide reference for bird diversity protection and habitat construction of urban river ecological corridors.   Method  In the spring of 2019, we conducted a field survey of bird species composition and plant community structure in the Wenyu River ecological corridor. Landscape pattern analysis was conducted after visual interpretation of the habitats in the corridor. Redundant analysis (RDA) was used to analyze the correlation between bird species composition and multi-scale environmental factors.   Result  The pattern characteristics within 50−200 m had the highest interpretation for the overall composition of birds. The composition of songbirds was mainly related to the Pielou index of trees in the community, the area of water and wetland within a small range, and some indexes of grassland and deciduous forest within a large range. The composition of terrestrial bird was mainly related to cropland and shrub. The composition of swimming birds and wading birds had a strong correlation with water body area and wetland area within a small range. The composition of raptorial birds was associated with wetland waters. In same ecological community, the composition of different reside pattern birds had different correlations with environmental factors. Most bird abundance was positively correlated with wetland area, wetland largest patch index and wetland cohesion index within 100 m, and waterbody splitting index within 2 000 m.   Conclusion  The relationship between birds of different ecological communities and various environmental factors is diverse, but the indices of water body and wetland have influence on birds of all ecological communities in the river ecological corridor. In the future construction of urban ecological corridors, we suggest to consider the habitat preferences of different bird communities, pay attention to the optimization of the habitat pattern of wetland water in corridors, and carry out the construction and protection of bird habitats for targeted species.
Abstract:
  Objective  Northern Shaanxi Province of northwestern China is an important area for the implementation of ecological restoration projects. This paper aims to reveal the spatial-temporal evolution and driving factors of habitat quality, then provide scientific reference for ecological construction.   Method  Based on the land use data, the InVEST model was used to evaluate the habitat quality in the northern Shaanxi Province of northwestern China from 2000 to 2020, the influencing factors were analyzed by the single factor detection and interactive detection methods of geographic detectors.   Result  (1) The land use structure in northern Shaanxi Province had changed significantly during the study period, cultivated land and unused land decreased by 3.83% and 1.91%, respectively. Grassland, forest land and construction land increased by 3.02%, 1.61% and 1.10%, respectively. The transfers of land use types were significantly different in varied periods, a large number of unused land was transformed into grassland from 1990 to 2000, while cultivated land was transformed into grassland and forest land after 2000. (2) The average value of habitat quality index in northern Shaanxi Province changed from 0.636 to 0.651 during the study period, with an increasing trend. The areas with high habitat quality were mainly distributed in woodland and grassland areas in the southern part, and the low value areas were mainly distributed in Mu Us Sandy Land in the northwestern part. The areas where the habitat quality grade increased were mainly distributed in the middle and northwest of the study area. (3) Land use type was the first factor affecting the temporal and spatial distribution of habitat quality, with the q value of 0.433. The interaction of any two factors on habitat quality was far greater than that of a single factor, natural factors and social factors dominated the temporal and spatial changes of habitat quality.   Conclusion  The spatial and temporal changes of habitat quality in northern Shaanxi Province are closely related to the distribution of land use types. Optimizing land use structure and reducing the impact of human activities are of great significance to improve the habitat quality in northern Shaanxi Province.
Abstract:
  Objective  Soil seed bank acts as a propagule source for revegetation to affiliate the restoration of degraded lands. The aim of this study was to investigate the responses of soil seed banks to altitude and slope aspect on natural steep slope and the relationship between soil seed banks and aboveground plant communities.   Method  Plant community investigation and soil seed bank collection were carried out on the shady and sunny slopes of the natural steep slope of Funiu Mountain, Henan Province of central China at an altitude of 600, 800 and 1 000 m. Then, soil seed bank composition and density, species diversity and richness of soil seed banks were estimated using the germination method.   Result  (1) Aboveground plant communities contained the number of 67 species and Fagaceae species was in the majority. A total of 62 species were identified in the soil seed banks and dominated by herbaceous species, which accounted for 82.26%, much higher than woody species. The species of Compositae occupied the largest proportion (24.19% of the total), followed by Gramineae and Caryophyllaceae (9.68% and 9.68% of the total, respectively). (2) The seed density was between 1 263 and 10 363 grain/m2, among which Cyperaceae seeds had the highest reserves, followed by Compositae and Gramineae. In terms of the reserve vertical structure, soil seeds were mainly distributed in 0−5 cm layer rather than 5−10 cm layer. (3) Species richness of arbor and shrub layer was positively correlated with altitude (P < 0.05), while herb layer species richness was negatively correlated with slope aspect (P < 0.05). In addition, there was positive correlation between seed density and altitude and slope aspect (P < 0.05). (4) The species composition of soil seed bank and aboveground plant communities showed relatively large differences with only 17 species in common and low species similarity coefficient ranging from 0.08 to 0.21. However, herb layer and soil seed banks displayed higher species similarity, and the structure of arbor layer and shrub layer appeared to provide certain explanations for the characteristics of seed banks.   Conclusion  We conclude that the species diversity of aboveground plant communities and soil seed banks generally increase with altitude. Characterized by the highest seed density and species diversity, soil seed banks on the sunny slope at an altitude of 1 000 m possess strong potential for vegetation restoration.
Abstract:
  Objective  The forest gaps caused by natural disturbance are the main driving force of the natural forest regeneration and the distribution, shape and extent of forest gaps can affect a series of ecological factors, such as sun light and soil moisture. The identification and characterization of forest gaps are of significance for understanding the dynamic changes of forests.  Method  The remote sensing of UAV can quickly obtain the three-dimensional spatial information of the forest. The study site is located in the UAV flight coverage at the Puer Sun River Reserve in Yunnan Province of southwestern China. The canopy height model (CHM) was derived from the point cloud data of UAV LiDAR . The fixed threshold method, relative height threshold method and object-oriented classification were used to identify forest gaps in CHM. The reference data from visual interpretation of images were used for accuracy assessment of forest gap identification. Finally, the best method was selected to describe the spatial characteristics of forest gaps.  Result  The experimental result showed that the overall accuracy of the fixed threshold method was 92.0%, which was higher than the relative height threshold method (66.0%) and object-oriented classification method (88.0%). The forest gaps in the study site area were mainly small and medium gaps, showing that there were fewer disturbance events. The average shape index of forest gaps in the study site was 1.97 and most of them with small shape index and less obvious edge effect. The spatial distribution of the gap was aggregation.   Conclusion  The spatial distribution of forest gaps and its spatial characteristics in small-scale subtropical natural forests can be mapped by UAV LiDAR data and the fixed threshold method.
Abstract:
  Objective  This paper aims to reveal the potential effects of competition on drought adaptability and growth decline of Pinus koraiensis, provide scientific basis for forest management.   Method  Based on the samples taken from natural forest in the south of Xiaoxing’anling Mountains, northeastern China, the dendrochronology method was used to analyze and compare the radial growth rate of P. koraiensis with different competition intensities and tree growth adaptabilities to extreme drought based on index of resistance (Rt), resilience (Rc), and restore elasticity (Rs).   Result  The tree ring width index and radial growth rate of P. koraiensis in the south of Xiaoxing’an Mountains reflected the growth decline appeared in the periods of 1980−1990, 1990−2000 and 2002−2017. Under varying competition intensities, the period and intensity of growth decline of P. koraiensis were different. The period of growth decline of P. koraiensis at middle and low competitive intensities was relatively consistent. During the rapid warming period from 1990 to 2000, the growth decline was not seen for P. koraiensis at high competitive intensity, while the growth decline for P. koraiensis at low competitive intensity was the most serious with the lowest value of −40.28%. The standard chronology of P. koraiensis with different competitive intensity was positively correlated with Palmer drought index (PDSI) from June of previous year to August of that year, and the high competitive index group reached a significant level from September of previous year to February of that year (P < 0.05). The resistance and resilience of P. koraiensis at high competition intensity to drought were weak, especially in severe drought period, competition intensified the sensitivity of trees to drought, and the higher the competition index (the greater the competition pressure was) was, the weaker the resistance and resilience of P. koraiensis to drought were. During the rapid warming period before 2000, the resilience of P. koraiensis to extreme drought under different competition intensities showed a downward trend, and the resilience of P. koraiensis to drought rebounded during the warming hiatus period around 2000.  Conclusion  With the increasing frequency of extreme drought events in the future, P. koraiensis may face a more severe recession. Competition affects the adaptability of trees to drought. Trees under high competition intensity are more sensitive to drought and have weaker adaptability, but don’t show more serious growth decline. Further research needs to be combined with in-depth analysis at different time and space scales to deal with the adverse effects of climate warming. It is of great significance to strengthen the research on the response of trees to drought for forest management and resource protection.
Abstract:
  Objective  Exploring the effects of long-term nitrogen deposition on the concentration of available nitrogen and soil N2O emissions in forest soil is important for controlling soil greenhouse gas emissions and improving the accuracy of regional carbon source sink assessment.   Method  The effect of N addition at different levels (control, 50 kg/(ha·year), 150 kg/(ha·year)) and forms (nitrate N: NaNO3; ammonium N: (NH4)2SO4 and mixed N: NH4NO3) on N2O emission from temperate plantation soils was analyzed by a field N addition control experiment using static chamber/gas chromatography.   Result  (1) The forms and levels of N addition caused significant accumulation of soil NH4+-N and NO3-N. The accumulation effect of NO3-N was much higher than that of NH4+-N. (2) Soil N2O emissions were promoted by different forms and levels of N additions. Low and high levels of NaNO3, (NH4)2SO4, and NH4NO3 additions increased annual cumulative soil N2O emissions by 87.39% and 146.79%, 86.13% and 74.91%, 98.67% and 50.50%, respectively. (3) Combined with the results of our previous study, we speculated that nitrification reaction was the dominant process of N2O emission from temperate plantation soils, and NH4+-N was more efficiently converted to N2O than NO3-N.   Conclusion  The effect of long-term nitrogen addition on soil N2O emissions is stage-specific. Therefore, we emphasize the importance of long-term field monitoring, and the contribution effect of N addition on soil N2O emissions from temperate forests may be overestimated if the experimental period is short.
Abstract:
  Objective  This paper aims to determine the characteristics of growth and development of secondary branches and their apical buds of cultivated Paeonia ludlowii as well as the differentiation process of flower buds in the cultivated site and the original site, then provide a reference for the introduction, cultivation, development and utilization of P. ludlowii.   Method  Taking the adult P. ludlowii introduced and cultivated in Luanchuan, Henan Province of Central China as the object, the growth and development dynamics of the secondary branches and its apical buds were observed. And the apical bud floral differentiation process in introduction site (Luanchuan and Lhasa) and original site (Nyingchi) was observed by paraffin section method.   Result  (1) In Luanchuan, the secondary branches of P. ludlowii grew from early May to mid-September, and the peak period was from early May to early June. However, some axillary buds of flowering branches were stagnant and did not develop into secondary branches. (2) In Luanchuan, the secondary branches of cultivated P. ludlowii had three growth types: the type 1, which accounted for 28.57%, its apical buds formed and began to differentiate in mid-July, blossom and bear fruits normally in following year. The type 2 was mainly located in the middle and lower parts of the flowering/fruit branches, apical buds formed but did not differentiate and there was only vegetative growth in the following year. The type 3 did not form apical bud, freeze-dried during winter and following spring. (3) In original site Nyingchi, 56.25% of the apical buds on the secondary branches of P. ludlowii differentiated and blossomed and bore fruits normally in following year, the secondary branches of type 3 were not observed. (4) The differentiation process of the apical bud on the secondary branches was the same in introduction site and original site. The apical bud finally formed a compound bud with a top flower bud, 2–3 lateral flower buds, axillary bud primordiums and leaf primordiums though six differentiation stages, the top flower bud differentiated earlier than the lateral flower buds. The axillary bud primordiums located at the base of the 3rd–4th leaf primordiums, which will develop new secondary branches on the flowering branches in the following year. (5) The start time and duration of flower bud differentiation in introduction site and original site were different. In Luanchuan, P. ludlowii began to differentiate late and lasted relatively longer (88–97 d), while in Lhasa and Nyingchi, it began to differentiate earlier and lasted relatively shorter (nearly 70 d).   Conclusion  The flower bud differentiation ratio of cultivated P. ludlowii in Luanchuan is low, the differentiation begins late and lasts long but it could form a stable secondary branch with normal flower bud differentiation, blossom and bear fruit.The natural environment of it could be a reference for site selection to introduce and cultivate P. ludlowii.
Abstract:
  Objective   Oriented strand board (OSB) is composed of cross-oriented layers consisting of thin and rectangular wooden flakes or strands, which are compressed and bonded together with synthetic resins. OSB is an important engineered wood product. The influence of application environment on the bending properties of OSB can provide necessary theoretical support for optimizing the processing technology and application method of OSB.   Method  Samples prepared from 13 mm thick OSB panel were conditioned under different relative humidity (RH) conditions. Three-point bending tests were performed to measure the fatigue deflection of OSB under cyclic loading, strain distribution was recorded using digital image correlation (DIC) simultaneously. This contributes to reveal the causes of deflection results.   Result  The increase of RH increased the moisture content and thickness of OSB, and enlarged the voids among wood strands and cracks in wood strands. The deflection of OSB increased significantly after conditioning at (95 ± 3)% RH, and after conditioning the samples at (65 ± 3)% RH, the deflection was still larger than the initial deflection. The samples’ deflection was close to their initial deflection if conditioning them at (95 ± 3)% RH and (65 ± 3)% RH without adding loading. The effect of loading cycles on the deflection was slight when the samples were conditioned at unchanged (65 ± 3)% RH. The deflection of the first cycle loading obviously increased, which was not found as increasing loading cycles. Strain distribution was homogeneous if the samples were conditioned only at (65 ± 3)% RH. The increase of moisture content could hamper the strain transfer and induce strain accumulation. Specifically, bending strain was prone to accumulate on the top and bottom surfaces, and shear strain would occur in the two opposite directions in high moisture content samples.   Conclusion  The findings of this work explore the effect of application conditions and loading cycles on the bending strength of OSB. The outputs of this work are helpful for optimizing the manufacturing strategies and enlarging application field of OSB.
Abstract:
  Objective  Sabina centrasiatica and Populus xjrtyschensis are two endemic tree species in Xinjiang of western China. Sabina centrasiatica is an endangered wild plant under Xinjiang Class I and National Class II key protection, Populus xjrtyschensis is drought resistant, barren, cold resistant and has a certain tolerance to saline alkali and barren soil. It is a valuable material for breeding improved varieties and an important plant for soil and water conservation. In the context of climate change, the study of the climate factors affecting the distribution of the two species and their response models to climate change plays an important role in the conservation of precious species in Xinjiang.   Method  In this paper, three of the four shared socioeconomic pathways (SSP245, SSP370 and SSP585) proposed by the researchers were used in the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). The maximum entropy method was used to predict the potential suitable areas of Sabina centrasiatica and Populus xjrtyschensis in the present (1970−2000) and future (2041−2060, 2061−2080) with 10 selected environmental variables, and to compare the changing trend of habitat areas of the two species and their response models to climate change in different periods in the future under the three greenhouse gas concentration paths.   Result  The temperature, precipitation and altitude were the main environmental factors affecting the distribution of Sabina centrasiatica and Populus xjrtyschensis. The Sabina centrasiatica is mainly distributed in the northern part of West Kunlun Mountain, Shache and Yecheng. In the future, the suitable area of Aksu area will be greatly reduced; the Populus xjrtyschensis is mainly distributed in the Erqis River and its tributaries, there will be a trend of moving from south to north in the future. The current total suitable areas of the two species are 673 909.49 and 976 827.81 km2, respectively. Under different climate scenarios in the future, the suitable areas of the two species will show a downward trend. The comparison of the response patterns of the two species to climate change indicated that the large temperature difference had reduced the suitable area of Sabina centrasiatica; and the decrease of suitable area of Populus xjrtyschensis was caused by the increase of annual average temperature.   Conclusion  Rising temperatures in the future will reduce the range of species distribution, so the research results can help the government optimize management, protect endangered wild plants and provide a theoretical basis for the protection of China’s natural population diversity.
Abstract:
  Objective  Under the background of the change of precipitation pattern caused by global warming, the study of the impact of throughfall reduction (rain reduction) on soil organic carbon (SOC) concentration and chemical composition of Castanopsis hystrix A.DC plantations in the southern subtropical region was carried out, and it will provide a scientific basis for accurately predicting the potential impact of climate change on the SOC sequestration function of plantation ecosystem.   Method  In 2012, in the Guangxi Youyiguan Forest Ecosystem Research Station, three throughfall reduction treatment plots and three control plots were randomly selected in a 29 years old C. hystrix plantation, each plot was 20 m × 20 m. In the sixth year of throughfall reduction treatment, the SOC concentration and chemical composition, total amount and components of litter, fine root biomass, soil microbial biomass and functional gene abundance in dry season (samplings in March) and wet season (samplings in July) were measured respectively. The effects of throughfall reduction on SOC concentration and chemical stability were analyzed.   Result  (1) Throughfall reduction significantly decreased soil water content in dry season and fine root biomass in dry and wet season, but there were no differences in the total litter, litter components and soil microbial biomass in dry and wet seasons. (2) In the dry season, throughfall reduction significantly reduced the soil alkyl C and alkyl C/O-alkyl C, but significantly increased the soil aromatic C and aromatic C/alkyl C. In the wet season, throughfall reduction had no effect on SOC concentration and chemical compositions. (3) Litterfall played a major role in the change of chemical compositions of SOC.   Conclusion  After six years of throughfall reduction treatment, although the content of SOC didn’t change significantly, the proportion of soil alkyl C with high stability reduced and the aromatization degree of SOC improved in the dry season. Therefore, the projected precipitation reduction scenario may reduce the chemical stability of SOC in C. hystrix plantations in the southern subtropical region.
Abstract:
  Objective  This paper aims to study the application of multiple machine learning algorithms in the prediction of bark thickness, to compare and analyze the influence of different individual tree factors on the prediction of bark thickness, and to provide new methods for the prediction of bark thickness.   Method  Four machine learning algorithms (neural network, support vector regression, decision tree, random forest) were constructed based on the bark thickness data of Dahurian larch (Larix gmelinii) in Daxing’anling Mountains of northeastern China. Their performance in predicting bark thickness was compared with six traditional bark thickness models. The determination coefficient (R2), root mean square error (RMSE), mean absolute error (MAE) and Akaike information criterion (AIC) were used to evaluate different models and algorithms.   Result  (1) Among the six basic models, Model 5 showed better prediction results. In the comparison between the basic model and the machine learning models, all the machine learning models fitted better accuracy than the traditional model Model 5 except for the CART4 model. (2) Among the machine learning models, the fitting and prediction accuracy of ANN4 and SVR3 were similar, and RF4 was the best. (3) The input variables of RF4 were diameter at breast height (DBH), tree height (H), and relative tree height (Hr). Based on the training samples, the R2 of random forest increased from 0.675 2 to 0.723 4, RMSE decreased from 0.575 5 to 0.531 0 compared with Model5. Based on the testing samples, the R2 of random forest increased from 0.666 9 to 0.710 5, RMSE decreased from 0.616 9 to 0.544 6 compared with Model 5.   Conclusion  Compared with the basic bark thickness model, random forest, support vector machine regression and artificial neural network in machine learning algorithm can improve the prediction accuracy of bark thickness. The prediction effect of random forest is slightly better and suitable for the prediction of bark thickness of Dahurian larch in this region.
Abstract:
Wood is a natural biological material inseparable from human life and its excellent aesthetic characteristics are widely used in the field of furniture and interior and exterior decoration of buildings. The unique color, texture and other appearance characteristics of wood will cause the visual stimulation from eye, and then cause the psychological and physiological response process. In terms of the visual stimulation representation of wood, as well as the experimental measurement and scientific evaluation of psychological and physiological response, the previous studies were mostly expressed by subjective questionnaires or evaluation scales. In recent years, through the use of advanced technology to monitor human psychological and physiological indicators, it provides a new perspective and method for quantitative research. In order to further sort out the psychological and physiological response activities caused by wood visual stimulation, focus on the research field of wood visual characteristics, this paper systematically generalizes the characterization methods of wood visual stimulation at home and abroad, and summarizes the main research contents and progress of human psychological and physiological response caused by wood visual stimulation. On the basis of comprehensive analysis, three scientific problems to be solved urgently in this research field were condensed: the accurate evaluation of human psychological and physiological response process caused by wood visual stimulation, the interaction and synergy mechanism of multi-sensory channels, and the impact of wood living environment on human psychological and physiological health. It aims to provide a theoretical basis for the visual design of wood products or the construction of comfort in wood indoor space, and to provide a technical reference path for the future research and application of wood environmental science, especially in the field of wood visual characteristics.
Abstract:
  Objective  The aim of the paper was to study the responses of street trees to impervious land coverage under canopy and to analyze resource utilization and allocation strategies of street trees with different leaf textures by comparing changes and trade-off and synergy in twig and leaf functional traits.   Method  Common greening tree species of Sophora japonica, Platanus acerifolia and Ligustrum lucidum in Jinan, Shandong Province of eastern China were selected to represent tree leaf textures of paper, wax and leather leaf, respectively, and 5 gradients of impermeable surface coverage were divided by 20% interval. Samples of twigs and leaves were obtained by typical sampling methods.   Result  (1) The sensitivity of branch and leaf traits of tree species with different leaf textures to the response of impervious ground coverage under the crown was different. The sensitivity of twig functional traits to the response of impervious ground coverage under the crown decreased significantly with the increase of thickness of wax layer on the leaf surface, and the leaf functional traits of Platanus acerifolia were more sensitive to the change of impervious ground coverage under the crown. However, the characters (leaf emergence intensity and branch leaf mass ratio) representing the relationship between branches and leaves were sensitive to the impervious ground coverage environment under the canopy. (2) The distribution of photosynthate decreased with the increase of impervious ground coverage, and the growth of branches and leaves, leaf space and leaf area decreased significantly with the increase of impervious ground coverage. With the increase of coverage degree of hardened ground, the three tree species adopted the way of reducing leaf area and maintaining leaf number to adapt to the environment. (3) Allometric growth relationship showed that, under the stress of impervious ground coverage, the resource input of trees to leaves was higher than that of twigs. In the interior of twigs, the resource input for the thickening growth of twigs was more than that for the elongation growth. The utilization mode of internal resources in leaves changed with the change of leaf texture: paper leaf trees tended to allocate more resources to the establishment of leaf resource acquisition organization, while leather leaf trees tended to allocate more resources to the establishment of leaf defense mechanism.  Conclusion  Impervious ground coverage environment will significantly affect the growth of branches and leaves of trees. The adaptation strategies adopted by the leaves of tree species with different leaf textures to the hardened surface environment are different. The paper leaf tree species tend to adopt the adaptation strategy of “low consumption-fast income”, while the leather leaf tree species tend to adopt the adaptation strategy of “high consumption- slow income”, and the adaptation strategy of wax leaf tree species is between the two.
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  Objective  This paper aims to explore the degree of variation of phenotypic traits and main source of phenotypic diversity of Sophora japonica resources in Beijing urban area, comprehensively evaluate S. japonica and directly select the best germplasm, then provide theoretical support and breeding materials for the breeding of improved varieties of S. japonica.  Method  In this study, 135 seedlings of S. japonica with DBH of 20 − 30 cm and tree age of about 23 years old were used as materials. According to their 26 phenotypic traits such as leaf position characteristics, fruit characteristics and crown width characteristics, the variation degree of phenotypic traits and the main sources of trait variation were analyzed by statistical methods such as analysis of variance, multiple comparison and principal component analysis, and the excellent S. japonica individuals were selected by quantitative evaluation and orientation.  Result  The average coefficient of variation of the phenotypic traits of S. japonica was 25.08%, and the variation range of the coefficient of variation was 7.01% − 264.44%, among them, the variation coefficients of dorsal fluff, number of lenticels, leaf size and shape and leaf color were larger, and the variation coefficients of fruit size and thousand-grain mass was smaller. From the analysis of variance and multiple comparisons, it can be seen that, except for the basal leaf length to width, crown round rate, dorsal fluff, the other phenotypic traits of the S. japonica among populations reached significant or extremely significant levels, it showed that there were wide variations in phenotypic traits in different populations of S. japonicus, and the degree of variation was different. The results of principal component analysis showed that the first eight principal components represented 81.931% of the morphological diversity of S. japonica, among which, leaf size, leaf color, leaf shape and fruit fullness were the main factors causing differences in phenotypic traits among varied populations. Targeted screening of different types of ornamental traits of S. japonica by means of comprehensive evaluation of principal components, 10 excellent germplasms for each of 3 types of S. japonica were screened out, and the best germplasm came from 2 populations of Xingfu Street (XFDJ) and Aolin West Road (ALXL) in Chaoyang District of Beijing.  Conclusion  The phenotypic traits of S. japonica germplasm resources in Beijing urban area are rich in phenotypic variation, and the degree of variation is high. Among them, the variation of leaf positions is the main source of phenotypic diversity, in addition, the variation degree of leaf and other vegetative organs of S. japonicus is greater than that of fruit reproductive organs, which provides abundant resources and great space for the selection and breeding of S. japonica varieties. In each of the three categories, 10 optimal germplasms were selected, which provide excellent propagation materials for the further collection, preservation and genetic improvement of the germplasm resources of S. japonica.
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  Objective  We aim to explore the distribution characteristics of forest soil bacterial communities in different elevations (900−1500 m) in Daiyun Mountain.   Method  We used high−throughput sequencing to study the composition and diversity of soil bacterial communities at different elevations, and analyzed the effect of environmental factors on soil dominant bacterial communities.   Result  (1) with the increasing of elevation, the content of soil total phosphorus showed a monotonic decreasing trend, the content of soil available phosphorus showed a unimodal trend, and the contents of soil total carbon and nitrogen presented a bimodal distribution trend. (2) In Daiyun Mountain, the dominant phyla bacteria in soil were the Proteobacteria, the Acidobacteria and the Actinobacteria (relative abundance > 10%). (3) The soil diversity indices, such as species number, Chao1 index, Shannon–Wiener index and ACE index, increased first and then decreased along the elevation gradients, reaching a maximum at 1100 m. (4) The co-occurrence network analysis further indicated that soil dominant bacterial community had an obviously modular structure at different elevations of Daiyun Mountain. The keystone taxa including the genera from the phylum of Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes and Verrucomicrobia, and the phylum of Proteobacteria had the maximum keystone genera.   Conclusion  The elevation, slope, pH value, soil total nitrogen, hydrolysable nitrogen, and available phosphorus were the main factors affecting the forest soil dominant bacterial community structure and diversity at the different elevations of Daiyun Mountain.
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  Objective  To explore the host preference and selectivity of Perina nuda to different banyan species.   Methods  4 species of host trees (Ficus macrocarpa, F. altissima, F. benjamina, and F. concinna) in Guangzhou were selected to feed on P. nuda and measure indicators such as their growth, development and food intake.   Results  The findings demonstrated that larval instar of P. nuda fed on 4 banyan species varied. During larval instar, P. nuda fed on F. microcarpa was 5th to 7th instar, P. nuda fed on F. altissima was 6th to 8th instar, and P. nuda fed on F. benjamina was 6th to 9th instar. This means that the development period of larval of P. nuda fed on F. benjamina was longest while the shortest period was the P. nuda fed on F. microcarpa. Additionally, body length, body weight and fecal weight of P. nuda larval fed on F. microcarpa were at the top among 4 banyan species. In the meanwhile, the 2nd to 7th instar larvae raised by F. microcarpa have the widest head capsule (the 1st instar larvae fed on F. altissima had the widest head capsule). Besides, the survival rates of P. nuda larvae reared by F. microcarpa and F. altissima were significantly higher than those of F. benjamina and F. concinna. Furthermore, the female adults of P. nuda larvae feeding on the F. microcarpa had the longest lifespan, while the male adults feeding on the F. altissima had the longest lifespan. It was also showed that the female adult had the shortest pre-ovulation period, and the single female laid the most eggs. Finally, it was found that the larvae fed on F. microcarpa at the 1st to 4th instars prefers to feed on F. altissima at the 5th instar, while the host preferences of 5th instar P. nuda larvae feeding on other three banyan species were not obvious.   Conclusion  There were significant differences in the selectivity and preference of P. nuda to 4 banyan species according to the results. Among them, the adaptability of P. nuda to F. microcarpa and F. altissima was strgonger than F. benjamina and F. concinna.
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  Objective   Saihanba Mechanical Forest Farm is the largest plantation Forest Farm in the world, it has been awarded the “Earth Guardian Award” by the United Nations in 2017. Thus, it is particularly important to scientifically evaluate the contribution of afforestation to the restoration of Saihanba forest ecological function. This study aims to analyze the current situation of Saihanba forest ecological function from different aspects and provide a theoretical basis for future forest management.   Method   The ecological function grade of various forests in Beimandian Forest Farm in Saihanba has been evaluated based on the technical specification for National Forest Resources Planning, Design and Investigation (GB/T 26424−2010) with 8 evaluation factors of forest volum, forest community structure, species structure, total vegetation coverage, canopy density, mean tree height and litter thickness.   Result   The forest ecological function index of Beimandian Forest Farm of Saihanba was 0.488, in which the stand with good ecological function grade accounted for 3.8%, the stand with medium ecological function grade accounted for 52.7%, the stand with bad ecological function grade accounted for 42.4% and the stand with worse ecological function accounted for 1.1%. The ecological function index of different stand origins was as follows: natural forest (0.545) > planted forest (0.474). The ecological function index of different forest types was as follows: mixed forest of needleleaf and broadleaf species (0.710) > mixed forest of broadleaf species (0.617) > secondary forest of natural platyphylla (0.535) > mixed forest of needleleaf species (0.487) > Larix principis-rupprechtii plantation (0.478) > Picea asperata plantation (0.443) > Pinus sylvestris var. mongolica plantation (0.429). The ecological function index of different age groups was as follows: over-mature forest (0.588) > middling forest (0.512) > near-mature forest (0.509) > mature forest (0.504) > young forest (0.434).   Conclusion   The forest ecological function of Beimandian Forest Farm has significantly improved after nearly 60 years of afforestation projects, which compared with sandy wasteland. However, the ecological function of artificial forests still has great space for improvement. The artificial forests should be subject to necessary management combined with the concept of near natural management.
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  Objective  In order to clarify and compare the characteristics of acorn qualities of Quercus and Castanopsis from different provenances, and further mine the potential utilization of these fruit resources, providing a reference for the selection and breeding, utilization, and protection of excellent fruit resources in China.   Method  The acorns were collected, including 6 Quercus species from 28 provenances and 7 Castanopsis species from 48 provenances, in 15 provinces (municipalities) in China, and the morphologies, nutrients, polyphenols and antioxidant capacities were determined, and then comprehensively evaluated by factor analysis.   Results  (1) At the level of morphological traits, the Quercus acorns were mostly ellipsoidal in morphologies, while the Castanopsis acorns were mostly nearly spherical. The size and weight in the former were about 1.5‒2 times of that in the latter. (2) At the level of kernel nutrient components, the soluble sugar contents in Quercus were 18.31–79.94 mg/g, and they were higher in Q. acutissima, Q. serrata and Q. mongolica than the average value in Quercus; while those in Castanopsis were lower (about 20.16–52.08 mg/g) at the overall level, but a few species such as C. sclerophylla and C. fissa reached the average level in Quercus. The starch contents in Quercus were 169.33–382.27 mg/g, whereas those in Castanopsis were 130.29–544.12 mg/g, which were higher than that in Quercus as a whole, but the starch in C. fissa was significantly lower than that of each species. The average values of total amino acid and soluble protein contents in both Quercus and Castanopsis were relatively low, but there were significant differences between species. (3) At the level of kernel functional components, the total polyphenol contents in Quercus were 54.64–242.9 mg/g, and while those in Castanopsis were 1.28–138.11 mg/g, the average contents in the former were about 4.5 times of that in the latter. Except for C. sclerophylla and C. fissa, the total polyphenol contents, between 1.28-4.66 mg/g, in other Castanopsis were extremely lower, and the change trends of total flavonoids and soluble tannins were similar to the total polyphenols. The contents of vitamin E in Quercus were higher than those in Castanopsis, which had very low contents except for C. sclerophylla and C. fissa with high polyphenols. Further test showed that the total polyphenols in Q. serrata from provenance 25 had the highest antioxidant activity with a high DPPH value of 82.98% in both Quercus and Castanopsis. (4) Based on the comprehensive score ranking, it can be concluded that the acorns from provenance 16 had the largest seed and the higher content of polyphenols, and the acorns from provenance 20 had a larger seed size, higher starch and polyphenols, and moderate soluble protein and total amino acid contents. The ten top ranking of acorn qualities by comprehensive evaluation were provenances 16, 17, 20, 14, 2, 24, 28, 8, 3, and 19.   Conclusion  The traits of phenotypes, nutrients, and functional components are rich in variation as well as higher degree of variation in the selected acorns of Quercus and Castanopsis germplasm resources in China, in which, ten optimal germplasms with top ranking were selected. These findings would provide valuable resources for the selection and breeding of excellent new varieties rich in starch or polyphenols in future.
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  Objective  Quercus variabilis is one of the dominant tree species in Beijing mountainous area. To explore the water use strategies, sap flow characteristics and their relationships of Q. variabilis could provide a theoretical reference for the study of the water process of the trees, and enhance the knowledge of forest plantation management.   Method  Based on the stable hydrogen and oxygen isotopes and the principle of thermal diffusion (pin type) stalk flow meter, water use sources and sap flow rates of Q. variabilis were measured in different seasons from 2015 to 2017, and the correlation between the two indicators were analyzed combined with meteorological data.   Results  (1) There were significant differences in sap flow activities in different stages of the non-growing season (November to December V.S. January to March). The average daily sap flow rate gradually increased by the end of the dormant period, and the sap flow rate was 2 × 10−4 ~ 3 × 10−4 cm/s, which was affected by environmental factors in the growing season with a large daily fluctuation of 1.5 × 10−3 to 1.7 × 10−3 cm/s. During the observation period, the sap flow rate differed significantly from June to October, but the difference from April to May was insignificant in different years; (2) the ratios of water use by Q. variabilis in different soil depths were relatively stable among different seasons, and the water in each soil layer was evenly supplied to the tree. In the non-growing season, the absorption and utilization ratios of water from the 0 ~ 40 cm, 40 ~ 80 cm, and 80 ~ 100 cm soil layers by Q. variabilis were (36.0 ± 3.5)%, (41.0 ± 1.6)%, and (23.0 ± 2.3)%, respectively. During the growing season, the utilization of soil water of 0-40 cm depth increased to (39.3 ± 2.6)%. The ratio of soil water utilization from 40 ~ 80 cm remained unchanged (40.0 ± 1.5)%, and soil water utilization of 80 ~ 100 cm decreased to (20.7 ± 1.8)%; (3) the average daily transpiration was negatively correlated with the use of 40 ~ 80 cm of soil water by Q. variabilis during the growing season and was positively correlated with the use of 80 ~ 100 cm of soil water.   Conclusion  Under the existing seasonal water use pattern of Q. variabilis, the increase in transpiration during the growing season will expand the absorption ratio of deep soil water, which is of great significance for the maintenance of transpiration of Q. variabilis.
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  Objective  Exploring the stability of soil structure and the changes of organic carbon- nitrogen content after the conversion of secondary forest into Pinus koraiensis plantation, and analyzing whether the mixing of different broad-leaved tree species with P. koraiensis could alleviate the decline of soil fertility caused by the pure P. koraiensis plantation, so as to provide a basis for the selection of mixed tree species and the targeted improvement of forest soil quality.   Method  Taking Juglans mandshurica-P. koraiensis plantation, Fraxinus mandshurica-P.koraiensis plantation, Phellodendron amurensis-P. koraiensis plantation and the pure P. koraiensis plantation built in Maoershan Forest Farm of Northeast Forestry University as the research object, and the secondary forest with main tree species of J. mandshurica and F. mandshurica as the reference, the soil aggregate classification was carried out by the combination of dry screening and wet screening, and the aggregate distribution, carbon- nitrogen content of each particle size were measured. Changes on soil aggregate stability and carbon-nitrogen distribution after the transformation of the secondary forest into P. koraiensis plantation were analyzed by calculating the parameters on stability of soil structure and the contribution rates of organic carbon- nitrogen in the aggregates with different particle sizes.  Result  After the secondary forest was transformed into P. koraiensis plantation, the mass fraction of > 2 mm particle size aggregates decreased, among which J. mandshurica-P. koraiensis plantation decreased by 17.94%, the mass fraction of < 0.053 mm particle size aggregates increased, and the pure P. koraiensis plantation increased by 45.78%. MWD and GMD of the soil decreased, and the stability of aggregates decreased. The contents of organic carbon and total nitrogen of aggregates with different particle sizes decreased in varying degrees, and the decline degree of J. mandshurica-P. koraiensis plantation was the lowest; The contribution rates of organic carbon and nitrogen in soil aggregates of the secondary forest and three mixed P. koraiensis plantations were mostly large aggregates, while the contribution rates of organic carbon and nitrogen in soil aggregates of the pure P. koraiensis plantation were mainly micro aggregates in 10 ~ 20 cm and 20 ~ 30 cm soil layers.   Conclusion  After secondary forest was transformed into P. koraiensis plantations, the soil aggregate stability, carbon and nitrogen content decreased in varying degrees. From the analysis of soil aggregate distribution, stability and organic carbon-nitrogen content, J. mandshurica, F. mandshurica and P. amurense were the suitable mixed species which could improve the nutritional status of P. koraiensis plantation.
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  Objective   The radial compression response of honeycomb rollers with multi dense degrees for forest harvester is studied under simulated working conditions, that is, clamping and overturning process during logging.   Method  15 kinds of rollers are divided into three grades according to different dense degrees. In order to obtain the quantitative exploration of mechanical and energy absorption characteristics, a combined theoretical and numerical study is designed. Then 3 of them is selected for manufacturing, and radial compression tests in linear elasticity phase are carried out. After monitoring with digital image correlation technology, the node deformation at the plastic hinge is compared. By comparing the results of simulation and test, the deformation mode of roller of double V-wing honeycomb (RDVH) with multi dense degrees are studied.   Result  The simulation results in the platform stage showed that, with the increase of dense degree by about 10%, the increase of equivalent stress of honeycomb roll is within 2 MPa, but the energy absorption is almost 6 times higher. The test results in the linear elastic stage showed that the same increase in dense degree acted as a trigger for a weight increase of 59.78%, while it has largely led to the promotion of contact force to about 3.4 times. The V mode deformation pattern is proposed in this work, which could be verified when the dispersion coefficient is less than 6%.   Conclusion  The compression response of RDVH with dense degrees in the range of 25%−40% could be shown as follows. To begin with, the dense degree, which is significantly induced by wall thickness and number of layers, has a remarkable nonlinear positive correlation with equivalent stress and energy absorption. Furthermore, under approximate dense degrees, the increase of wall thickness could be capable to meet higher compressive strength, while the decrease of the number of layers would contribute to the improvement of energy absorption. Finally, the deformation mechanism of RDVH in circumferential directions showed uneven auxeticity.
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  Objective  To explore the effects of uniconazole on the physiological characteristics and microstructure of potted Paeonia lactiflora, in order to provide a certain reference for the commercial production of potted P. lactiflora.   Method  The cultivar ‘Dafugui’ was used as the experimental material, the leaves were sprayed with uniconazole (40 mg/L) as the treatment, and the leaves were sprayed with clean water (0 mg/L) as the control. Physiological characteristics and microstructure of the leaves and roots were measured and observed at four different growth and development stages (leaf-expansion stage, flower-bud stage, pigmented stage, full-flowering stage) of potted P. lactiflora.   Result  The results showed that: compared with the control, uniconazole treatment can significantly reduce the production and accumulation of thiobarbituric acid reactive substances (TBARS) in the leaves and roots of potted P. lactiflora, increase cell membrane permeability, maintain cell membrane stability, and thereby increase the adaptability of potted P. lactiflora to the environment. The total chlorophyll and carotenoid contents of potted P. lactiflora initially increased but then decreased and were highest at the pigmented stage. After the treatment of uniconazole, the leaves of potted P. lactiflora are thicker with the sponge and palisade tissue cells arranging tightly and orderly. Compared with the control, the proportion of the root stele was larger, the proportion of the cortical cell became smaller.   Conclusion  Studies have shown that foliar spraying uniconazole can effectively improve the environmental adaptability of potted P. lactiflora, increase the contents of photosynthetic pigment, and change the internal tissue structure of leaves and roots. Foliar spraying with uniconazole may be an effective measure for potted plants production.
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  Objective  The stormwater problem has become a key restrictive factor for the development of shallow mountain areas and the low impact development (LID) of green space is an important means to solve such problem in shallow mountain areas. Forming an optimization method for LID controls distribution, for multi-objective such as runoff control and cost, can provide important technical support for the efficient solution of stormwater problems in shallow mountain areas, and contribute to the future high-quality development of this areas.  Method  Based on the characteristics of green space planning and design and runoff in shallow mountain area, the study forms a platform for optimal distribution of LID controls by D8 and NSGA-Ⅱ coupled algorithm, which realizes spatial quantitative optimization of the type and scale of LID controls based on collaborative optimization of runoff control and cost, in addition, Westmount country park in Shijiazhuang city is taken as the experimental object to verify the feasibility of the method.  Result  24, 30 and 30 optimal solution sets for the optimal distribution of LID controls of experimental object are got in the simulated2-hour rainfall event under return periods of 5-year, 10-year and 20-year; The ‘ideal investment upper limit point’ of each simulated rainfall event is 75.141 million yuan, 66.344 million yuan and 60.651 million yuan respectively; Visual results of the distribution of most efficient cost based on ArcGIS show that raingarden, permeable pavement and water are scattered, and vegetative swale is scattered in small-scale linear distribution.   Conclusion  D8 and NSGA-Ⅱ coupled algorithm can well match the LID of green space in shallow mountain area, and simplify the cumbersome design process of LID in traditional green space; there is marginal diminishing benefit between peak flow of runoff and LID controls cost, which accelerates with the increase of rainfall return period; the permeable pavement and raingarden have more cost performance than other LID controls; the visual simulation results of the experimental object basically accord with the principle and pattern in real design, which verifies the feasibility and rationality of the method; in order to improve the rationality and guidance of simulated results of distribution, the further research should focus on the collaborative method for optimal distribution of LID controls and green space planning and design.
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  Objective  In this paper, the antibacterial activity of alkaloids from different parts (root, stem, leaf and fruit) of Berberis poiretii was evaluated, it provides a theoretical basis for broadening the application fields of whole plant and developing new natural food preservatives.  Method  Taking the diameter of bacteriostatic zone, the lowest bacteriostatic concentration and the lowest bacteriostatic concentration as the examination index, the Oxford Cup bacteriostatic method was used, to study the inhibitory effects of alkaloids from different growth sites on four food−borne pathogens (Escherichia coli, Staphylococcus aureus, Salmonella spp., Bacillus subtilis), the types and contents of alkaloids were determined by High−performance liquid chromatography method.  Results  Before and after purification, the alkaloids from 4 different parts of Berberis poiretii showed positive dose−effect relationship to four common food−borne pathogenic bacteria, Escherichia coli, Staphylococcus aureus, Salmonella spp., Bacillus subtilis. When the concentration of alkaloids was 60 g/L, the diameter of bacteriostatic zone was more than 20 mm. The minimum inhibitory concentration (MIC) to Escherichia coli, Salmonella spp. and Bacillus subtilis was 1.25 g/L, minimum bactericidal concentration (MBC) was 2.50 g/L, and the MIC to Staphylococcus aureus was 2.50 g/L, MBC was 5.00 g/L. When the concentration of alkaloid was 40 g/L, the diameter of bacteriostatic zone was more than 20 mm. The results showed that the MIC for Escherichia coli and Salmonella spp. were 0.31 g/L, MBC were 0.63 g/L, and the MIC for Bacillus subtilis and Salmonella spp. was 0.63 g/L, respectively, MBC was 1.25 g/L. The results of HPLC showed that the purified alkaloids were berberine (0.28–41.69 g), jatrorrhizine (0.32–12.67 g) and palmatine (0.25–17.09 g) .  Conclusion  The root, stem and fruit of Berberis poiretii had stronger bacteriostatic effect on the tested strains, but the leaf had weaker bacteriostatic effect. The basic alkaloid monomers in 4 different growing parts were the same, but the content of the monomers was significantly different. When the concentration of alkaloid was 60 g/L, the order of bacteriostasis was fruit > root > stem > leaf, and the order of bacteriostasis was root > stem > fruit > leaf.
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  Objective  This paper aims to explore the mechanism of the difference in the food spectrum of larvae of Dioryctria sylvestrella and D. abietella.  Method  We observed the ultrastructures of the mouthparts and sensilla of the two Dioryctria larvae by scanning electron microscopy (SEM) observation.   Result  The SEM results showed that there were differences in the structure of the mouthparts of these two species larvae. The epipharynx of D. sylvestrella larvae has ossification in two places, while D. abietella larvae has three places. There were more incisors on the upper mandibular of D. sylvestrella larvae than that on D. abietella larvae. The spinneret bears an oriffis of D. sylvestrella larvae were larger than that of D. abietella larvae. Both of the two species of Dioryctria larvae have five kinds of sensilla and one kind of keratinous teeth on the mouthparts. They were sensilla trichomes, sensilla chaetica, sensilla basiconca, sensilla styloconica, sensillum digitiformium, and spiculesteeth, respestively. However, there were differences in the size and distribution of the same sensilla between the two species. The sensilla basiconca at the junction of the first and second segments counted from the end of the maxillary palp of D.sylvestrella larvae is type Ⅱ, while the sensilla at the same place of D. abietella larvae is type Ⅲ. There were also have differences in the length and shape of two species of Dioryctria larvae in the same type of sensilla.   Conclusions  The difference in the structure of the mouthparts of the two Dioryctria larvae was one of the reasons for the different feeding behaviors.In addition, the difference in length and shape between the same sensilla has a certain effect on the feeding behavior of the two Dioryctria larvae.The five kinds of sensilla distributed on the mouthparts of the two Dioryctria larvae play an important role in the perception of the hardness of the host plant tissue, the volatiles on the surface of the host, and the airflow, and help the larvae to locate the host.This study clarified the structure of mouthparts, types, quantity and distribution of the sensilla of the larvae of these two species of Dioryctria larvae,and discussed the functions of the sensilla. It expected to lay the foundation for further of exploring the difference mechanism of the food spectrum of the two species of Dioryctria larvae.
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  Objectives  The adaptive mechanism of walnut was explored under short-term potassium stress.   Methods  Walnut seedlings were treated with different levels of potassium deficiency for 75 Days: Control (CK), moderate potassium deficiency (MK) and severe potassium deficiency (SK), respectively. The related indexes were measured every 15 days, and the effects of potassium deficiency stress on the growth and physiology of walnut seedlings were analyzed.   Results  (1) Under K deficiency stress, the aboveground biomass, root biomass, chlorophyll a, chlorophyll b and carotenoid contents of walnut seedlings were significantly lower than those of CK (control treatment), and the overall decrease was more obvious with the aggravation of K deficiency degree and the extension of treatment time. (2) Compared with CK treatment, Fv/Fm, ΦPSⅡ, ETR and qP of walnut seedlings decreased significantly at the late stage of MK and SK (60−75 days). (3) As the processing time increases, CAT of walnut seedlings increased at first and then decreased under different K deficiency treatments. MK, SK and CK treatments reached the maximum at 30, 45 and 60 days, respectively. SOD activity of MK and SK increased, but POD activity decreased under severe K deficiency. From the middle stage of treatment (30 days) , the content of MDA in walnut seedlings increased with the increase of stress degree.   Conclusions  The growth of root and aboveground parts, and the synthesis of photosynthetic pigments of walnut were significantly affected by potassium deficiency stress. However, the walnut could increase the input to root system through self-regulation to improve its absorption capacity, and consume the excess excitation energy of PSⅡ reaction center by increasing heat dissipation, in order to reduce the damage of stress on photosynthetic apparatus. Furtherly, the walnut could mobilize its enzymatic antioxidant system, and produce certain resistance to potassium deficiency stress.
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  Objective  This study aims to investigate the response characteristics of soil aggregate distribution and carbon (C) and nitrogen (N) content under different N addition conditions, in order to provide data support for soil C sequestration mechanism in alpine meadow under the background of N deposition.   Method  In 2014, a long-term N addition platform was established in an alpine meadow on the Qinghai-Tibet Plateau. A completely randomized block design was used to simulate N deposition with six N addition levels: 0 g/(m2·year) (N0, control), 2 g/(m2·year) (N2), 4 g/(m2·year) (N4), 8 g/(m2·year) (N8), 16 g/(m2·year) (N16), 32 g/(m2·year) (N32). Macroaggregates (0.25−2 mm), microaggregates (0.053−0.25 mm), silt and clay (< 0.053 mm) were obtained by wet sieving method, and the organic C and total N contents of soil aggregates were determined.   Result  The results showed that the mass proportion of macroaggregates (79%) was significantly higher than that of silt and clay (13%) and microaggregates (8%) (P < 0.05). There was no significant difference in the distribution of soil aggregates under different N addition gradient (P > 0.05), whereas the mean weight diameter of soil aggregates did not change with N addition (P > 0.05), which could attribute to the trade off between the positive effect of N addition on root biomass and the decreased microbial activity. Moreover, N addition decreased the organic C content of macroaggregates and microaggregates, but increased the organic C content of silt and clay (P > 0.05). Compared to the control, N addition decreased on average the total N content of macroaggregates and microaggregates by 2% and 12%, respectively (P > 0.05). The C/N ratio of all aggregates significantly decreased under N addition (P < 0.05).   Conclusion  The C/N ratios of different size of soil aggregate decreased, indicating the acceleration of SOC mineralization in alpine meadow under increased N deposition.
Abstract:
  Objective  To reveal the influence rule of forest type and light-felling intensity on the carbon source and sink of Korean pine forests by planting conifer and reserving broad-leaved tree (PCRBT), and to provide basis for the restoration of zonal climax vegetation broad-leaved Korean pine forest.   Method  The annual net carbon sequestration of vegetation, net carbon emission (CH4, CO2) of soil heterotrophic respiration with related environmental factors(temperature, water content of soil, organic carbon, total nitrogen and so on) under different light-felling intensity(Control, Low-intensity LF-1/7, Heavy-intensity LF-1/3) were measured simultaneously by Static chamber-gas chromatograph and relative growth equation in three types of Korean pine forests by PCRB (Mongolian oak-Korean pine forest and white birch-Korean pine forest, which Korean pine planted under secondary crown for 25 ~ 35 years and light-felling for 25 ~ 30 years) in temperate in Xiaoxing’an Mountains., in order to reveal the influence of forest type and light-felling intensity on the carbon source/sink of Korean pine forest according to the net carbon balance of the ecosystem.   Results  (1) The annual average efflux of soil CO2 (159.94 ~ 207.43 mg/(m2·h)) in three forest types, were influenced by both the intensity of light-felling (heavy-intensity LF significantly increased 18.9% from Mongolian oak-Korean pine forest), and the forest type (control was white birch-Korean pine forest significantly higher than aspen-Korean pine forest and Mongolian oak-Korean pine forest, low, and heavy LF had no significant impacts among three forest types); low, and heavy LF had no significant impacts on the annual average flux of soil CH4 uptake (−0.047 ~ −0.028 mg/(m2·h)) from three forest types but white birch-Korean pine forest and aspen-Korean pine forest has significantly higher than Mongolian oak-Korean pine forest. (2) Low, and heavy-intensity LF made the annual net carbon sequestration of vegetation (1.66 ~ 3.99 t/(ha·year)) from three forest types had no significant effect, but white birch-Korean pine forest significantly higher (105.4% ~ 124.1% and 31.0% ~ 32.6%) than aspen-Korean pine forest and Mongolian oak-Korean pine forest , aspen-Korean pine forest has significantly higher(55.7% ~ 71.1%) than Mongolian oak-Korean pine forest. (3) Low-intensity LF had no significant impacts on carbon sink in Mongolian oak-Korean pine forest (−1.93 ~ −1.12 t/(ha·year)) and aspen-Korean pine forest (−0.65 ~ −1.03 t/(ha·year)) and White birch-Korean pine forest (−0.13 ~ 0.46 t/(ha·year)), but the level and direction of the effect of heavy-intensity LF were closely related to the forest type, Mongolian oak-Korean pine forest has significantly increased about 72.3%, White birch-Korean pine forest converted into carbon source, aspen-Korean pine forest has slightly increased carbon source.  Conclusion  Therefore, considering the maintenance of forest carbon sink in Korean pine forests by planting conifer and reserving broad-leaved tree, the faster recovering White birch-Korean pine forest and aspen-Korean pine forest was more appropriate to take heavy-intensity LF, while the slower recovering Mongolian oak-Korean pine forest are suitable to be low-intensity LF.
Abstract:
  Objective  We analyzed the characteristics of JAZ gene family in Pinus tabuliformis and its functional domain of interaction with gibberellin negative regulator DELLA protein, in order to lay a foundation for the analysis of jasmonic acid (JA) -gibberellin (GA) mediated growth/defense balance strategy in conifers with JAZ-DELLA as the core module.   Method  This study screened and identified all JAZ genes based on the whole genome data of Pinus tabuliformis, and analyzed the basic characteristics of P. tabuliformis JAZ gene family; At the same time, a phylogenetic tree of multi-species JAZ gene family was constructed to parsed the characteristics of P. tabuliformis JAZ gene family in the phylogenetic process. Furthermore, the functional domain of interaction between P. tabuliformis JAZ gene family and DELLA protein was identified by yeast two-hybrid technique.   Result  The results show that: there were 53 JAZ genes in Pinus tabuliformis, and the JAZ gene family of P. tabuliformis not only had TIFY and Jas conserved structures, but also evolved more abundant changes in the degron sequence. The promoter regions of multiple members of the JAZ gene family in P. tabuliformis contained cis-acting elements that respond to JA and GA, and had a close evolutionary distance from several JAZ proteins in model plants. Further experiments showed that the Jas domains of 5 JAZ proteins (TIFY 4, TIFY11, TIFY16, TIFY25, and TIFY59) in P. tabuliformis were interacted with PtDPL (DELLA-like), and identified the functional motif of JAZ-DELLA was Jas motif in P. tabuliformis.   Conclusion  This study clarified the basic sequence characteristics of JAZ gene family and identified the functional motif of JAZ and DELLA interaction in P. tabuliformis. At the same time, it also supplemented an important basis for the further study of JAZ gene family and JA-GA signaling pathway in conifers.
Abstract:
  Objective  The properties of wood are determined by the composition and characteristics of xylem cell wall,. The investigation on molecular regulation of xylem cell wall formation has been an important foundation for wood quality improvement. In this study, the molecular regulatory mechanisms in the process of the regeneration of the primary wall in the protoplast of birch (Betula platyphylla) xylem were analyzed and the important regulatory genes were identified, aims to provid data and materials for the study of wood properties.   Method  The protoplasts of birch xylem cultured for 0 h and 2 h were used as materials respectively, and the regeneration process of primary cell wall was observed by staining with Calcofluor White. The differentially expressed genes (DEGs) and differential metabolic pathways they participated before and after the regeneration of the primary wall was compared by transcriptomic analysis. The detected DEGs were aligned with GO, KEGG and PlantTFDB.   Result  Observation by fluorescence microscopy showed that protoplasts had no cell walls after enzymatic digestion and the primary cell walls had been regenerated after two hours of culture. The DEGs were screened using |log2(FC)| ≥ 1(fold change, FC) and q < 0.05 as the parameters. The results showed that compared with the protoplasts without cell wall, 4396 up-regulated genes and 4056 down-regulated genes were detected in the protoplasts cultured for 2 h, with a total number of 8452 DEGs. In the GO database, there were 10 significantly up-regulated terms. KEGG analysis noted 10 significantly different metabolic pathways. Total of 360 differentially expressed transcription factors from 16 families was annotated in PlantTFDB database. The GO database annotation results showed that DNA replication and cell cycle related genes were up-regulated in the cell wall regeneration lines compare that in control. The results of KEGG database annotation showed that genes involved in glutathione, α-linolenic acid and other stress-related metabolism genes were down-regulated, and pectinester related genes were up-regulated. PlantTFDB annotation results showed that bHLH, NAC, MYB, bZIP and other transcription factors closely related to cell wall biosynthesis were differentially expressed.   Conclusion  Above results showed that xylem protoplasts were in a state of cell wall regeneration and division preparation at 2 h culture. DNA replication, cell cycle, polysaccharide biosynthesis and other related genes play a regulatory role in xylem protoplast culture and primary cell wall formation of B. platyphylla.
Abstract:
  Objective  Forest fire risk assessment is to describe the potential occurrence of forest fire and the direct or indirect fire impacts on the environment at the landscape scale by using qualitative and/or quantitative indicators. Identifying the areas with high fire risk is the base of forest fire management. Comprehensive assessment on forest fire risk for a region based on burn probability, potential fire behavior, and exposure provides a guide for local fire agency to carry out fire and fuel management.   Method  We simulated the burn probability, potential fire intensity, spreading speed, and fire types on the landscape scale for the forests in the Subtropical Forestry Experimental Center by using the burn probability model (Burn-P3). The potential fire impacts on surrounding communities and water sources were analyzed for exposure. We also analyzed the spatial characteristics of fire risk, burn probability, and potential fire behavior of every vegetation type. A comprehensive assessment model on fire risk was constructed by using analytic hierarchy process.   Result  The fire simulation results showed that the average burn probability of the study area was 0.0401, and the areas with high and very high burn probability accounted for 5.3% and 2.3%, respectively. The fire types are mainly surface fire and intermittent crown fire. The average fire intensity and spread speed are 2 043.6 kW/m2 and 2.5 m/min, respectively. The areas with high and very high fire behavior index accounted for 17.3% and 6.2% of the total areas, respectively. The coniferous and broad-leaved mixed forest has the highest rating on burn probability and potential fire behavior index. The broad-leaved forest has the lowest grade on burn probability and fire behavior index, but shows the highest exposure. The comprehensive assessment results on fire risk showed that the areas with high and very high risk account for 19.7% and 6.5%, respectively. The fire risk of coniferous and broad-leaved mixed forest is higher than that of the other vegetation types.   Conclusion  Most of the study area has low burn probability and high potential fire behavior index. The forests near towns and water sources showed high fire risks, which should be the key areas for fire management in the future. It is necessary to carry out fuel cleaning measures to reduce fuel ladder and surface inflammable fuels in coniferous forest and coniferous and broad-leaved mixed forest in order to reduce their fire risk.
Abstract:
  Objective  By investigating the changes trend of street trees structure in Beijing from 2010 to 2020, the purpose of the research is to identify the main challenges and give references for street trees establishment and management in the future.   Method  Typical sampling methods and the same plots were used to investigate every street tree within Sixth ring road in Beijing from June to September in 2010 and 2020. The variation of ten years in street tree species composition, utilization frequency, crown diameter and species important value in Beijing were analyzed from different perspectives.   Result  Six families, ten genera and eight species have been increased during the last ten years in Beijing, and all of them were occasional species. The proportion of arbor and shrub has also increased. The street trees are mainly native species and deciduous species, with a higher proportion of deciduous species. The total proportion of top ten street tree species ranking by utilization frequency has increased, and proportion of Fraxinus chinensis trees was the highest one, while the decrease in utilization frequency of Rosa xanthina was the highest one in recent decade. The important value of Sophora japonica was still much higher than other street tree species though it was decreased by 8.2%. The average crown diameter of street trees decreased by 0.1m for massiveness of new planted trees. The proportion of street trees in the 1st and 5th crown diameter class has decreased. The top ten street tree species ranking by average crown diameter range has narrowed, and the Platanus acerifolia has been the most decreased species in the 1st crown diameter class.   Conclusion  The decreasing tree species diversity, and relatively sample tree species composition and higher proportion of single species are the main problems while could affect the stability of urban road vegetation ecosystem in Beijing. Therefore, the range of tree species selection should be broaden, mixed configuration with more broad-leaved deciduous tree species, evergreen shrubs and herbs should be constructed. The cultivation and application of native species should be strengthened, while the high-value exotic tree species should be introduced appropriately. At the same time, we should also protect the tree crown structure to enhance the shading effect of street trees in the urban greening.
Abstract:
  Objective  Plant diversity is not only the basis of human survival and development, but also an important part of urban ecosystem. In view of the lack of evaluation standard of plant diversity for urbanization areas, this study attempts to establish an evaluation system of plant diversity for Beijing urbanization areas.   Method  In this study, nine districts with a high degree of urbanization in Beijing were taken as the evaluation units. Through the collection of historical data and field investigation in key areas, the evaluation system of plant diversity in urbanization areas of Beijing was constructed by six indicators, including richness of vascular plants species, diversity of ecosystem types, species endemism, degree of invasion of invasive alien species, rate of urban green space and richness of ancient and famous trees. The weight of each indicator was determined by regional diversity evaluation standard issued by the Ministry of Ecology and Environment, combined with expert opinions.   Result  The plant diversity index of the nine districts in the study areas is relatively high, 88.39 in Haidian, 61.69 in Shijingshan, 60.30 in Shunyi, 49.75 in Fengtai, 42.33 in Chaoyang, 42.01 in Daxing, 41.55 in Tongzhou, 38.14 in Dongcheng and Xicheng; The evaluation grade of plant diversity is “Very rich” in Haidian, Shijingshan and Shunyi, and “rich” in other districts.   Conclusion  Taking district as basic unit, the evaluation system for plant diversity in urbanization areas can reflect the overall status of plant diversity in Beijing. Evaluation result is the quantitative index for the assessment of ecological civilization construction in each district. Moreover, it can provide scientific basis for the conservation and management of biodiversity in Beijing. In the future, it is suggested that the regional grid (10 km × 10 km) be used as the evaluation unit, and the indicators of the evaluation system should be continuously optimized. In this way, the evaluation results will be more fair and reliable, making the later protection measures more operable.
Abstract:
  Objective  This paper aims to explore the effects of different thinning intensities on canopy fuel characteristics and potential crown fire behavior of Platycladus orientalis in Xishan Experimental Forest Farm in Beijing, so as to provide reference for the regulation of canopy fuel and the prevention of high-energy active crown fire.  Method  Taking Platycladus orientalis in Xishan Experimental Forest Farm in Beijing as the research object, three thinning intensities ( low, 15%; moderate, 35%; high, 50% ) and the control were set up, and three repeated sample plots were set for each thinning intensity. Based on the canopy fuel parameters (branch number, length, base diameter) obtained by the standard branch method, a linear regression model was established for canopy fuel load, and the canopy bulk density was further calculated. The effects of different thinning intensity on canopy fuel characteristics (canopy fuel load and canopy bulk density) were discussed by single factor analysis of variance (ANOVA). Using BehavePlus 5.0 software, according to the fuel moisture content and meteorological conditions of the sample plots, the humidity condition and 10 m high altitude wind speed (0 − 18 m/s) were set to explore the effects of different thinning intensity on the potential crown fire behavior indexes (crown fire spread rate, fire line intensity, flame length, calorific value per unit area, etc.). According to the crown fire transformation model, the effect of thinning on the occurrence of active crown fire was further studied.   Result  (1) The characteristics of canopy fuel in different thinning intensities were different and the difference was the most significant between moderate thinning and control. Canopy fuel load and canopy bulk density decreased with the increase of thinning intensity, the former decreased from 3.280 to 0.540 kg/m2 and the latter decreased from 0.478 to 0.056 kg/m3. (2) After thinning with different intensities, the canopy fuel load and canopy bulk density distribution increased at first and then decreased with the increase of tree height. (3) The index of potential crown fire behavior under moderate thinning intensity was significantly different from control, in which the fire line intensity, flame length and calorific value per unit area decreased with the increase of thinning intensity. The canopy fire spread rate after thinning was lower than that of control, but did not change with the change of thinning intensity, and the critical crown fire spread rate increased with the increase of thinning intensity. Active crown fire will occur in the sample plot without thinning and low thinning intensity, and will not occur in the sample plot with moderate and high thinning intensity. With the increase of thinning intensity, the required 10 m high-altitude wind speed for active crown fire gradually increased from 6 to 8 m/s, the fire line intensity decreased from 6 930 to 5 829 kW/m, the flame length decreased from 9.7 to 8.6 m, the calorific value per unit area decreased from 47 817 to 40 667 kJ/m2, and the crown fire spread rate increased from 8.7 to 8.9 m/s.   Conclusion  Thinning affects canopy fuel characteristics and potential crown fire behavior indicators. Moderate thinning intensity has significant influence on canopy fuel characteristics and potential crown fire behavior indexes. By reducing canopy bulk density, the potential crown fire behavior can be effectively reduced and the occurrence of active canopy fire can be reduced. For Platycladus orientalis, moderate thinning is recommended in the regulation of canopy fuel considering both economic and ecological benefits.
2022, 44(5): 1-2.  
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Abstract:
Forest Sciences
Abstract:
  Objective  Poplar seed hair is produced by the development of epidermal cells of the placenta at the base of ovary and it has become one of the environmental problems in northern cities of China in recent years. At present, the research on poplar seed hair is not in-depth. In this study, two genes (PeCFL1 and PeCFL2), which are differentially expressed during the development of poplar ovary and related to cotton fiber development, were selected as candidate genes for the regulation of seed hair development. We studied the spatio-temporal specificity of PeCFL1 and PeCFL2 genes expressed in Populus × euramericana ‘Bofeng 3’ to lay a foundation for further study on the regulation of the two genes during the development of poplar seed hair and improvement of poplar varieties by genetic engineering.   Method  After 4, 5, 6, 7, 8, 12 days of hydroponic culture, the female inflorescences of Populus × euramericana ‘Bofeng 3’ were collected, fixed, paraffin embedded and sliced to observe the ovary development and the morphogenesis of poplar seed hair. Real time quantitative PCR was used to detect the expression patterns of PeCFL1 and PeCFL2 genes during the development of female inflorescence and in vegetative organs such as roots, stems and leaves of ‘Bofeng 3’ poplar. The tissue expression specificity of PeCFL1 and PeCFL2 genes in poplar flower organs was detected by in situ hybridization, and the temporal and spatial expression patterns of candidate genes PeCFL1 and PeCFL2 related to the regulation of poplar floc development were revealed.  Result  After 12 days of hydroponic culture, fibrous structure appeared at the bottom of ovary placentation and poplar seed hair began to form. PeCFL1 and PeCFL2 were expressed in roots, stems, leaves and axillary buds of female flower branches of ‘Bofeng 3’ poplar. For the female inflorescence of hydroponic culture, a small amount of PeCFL1 and PeCFL2 were expressed from the 4th to the 7th day, and the expression levels began to increase significantly after the 8th day. Then the expression levels continued to increase significantly on the 12th day, at the same time, the fibrous structure at the bottom of placenta could be seen in paraffin section. The results of in situ hybridization showed that PeCFL1 and PeCFL2 genes were expressed in ovary wall and placenta of poplar ovary.  Conclusion  The expression of PeCFL1 and PeCFL2 is significantly increased when the fibrous structure appeared at the bottom of the placentation in female flowers of Populus × euramericana ‘Bofeng 3’, and they are specifically expressed in the fibrous structure at the bottom of the placenta and the ovary wall, indicating that they are closely related to the regulation of seed hair development, and can be used as target genes for genetic engineering improvement of poplar seed hair.
Abstract:
  Objective  This paper intends to analyze the mobile mRNA in heterologous grafted plants, explore the effects of sequence and functional characteristics on mRNA transfer, reveal the principle of mRNA transfer, and provide a theoretical basis for the directional regulation of grafting.   Method  With the transcriptome data of the various grafts, the coding region length and GC content of transfer mRNAs were calculated by Tbtools software and their correlation with mRNA transfer was further analyzed by Excel software. The sequence identity analysis via BLASTP was applied to find out the co-transfer mRNAs in different grafts. Function annotation and metabolic pathways analysis of the mRNAs were conducted through GO and KEGG database.   Result  (1) The average length of root-to-shoot or shoot-to-root transfer mRNA was 1 573 and 1 547, respectively. The mRNA transfer ratio increased progressively along with the mRNA length increasing. Obviously, the transfer ratio of the root-to-shoot mRNA was larger than that of the shoot-to-root mRNAs, and the tendency was more significant with the mRNA length increasing. (2) When the GC content was 52% − 54%, the mRNA transfer rate from stem to root was the highest (3.66%), and when the GC content was 46% − 48%, the mRNA transfer rate from root to stem was the highest (4.71%). (3) Co-transfer mRNA analysis showed 1 032 root to shoot and 1 727 shoot to root mRNA were present in at least 2 grafts, which mainly participated in carbon metabolism, amino acid synthesis, and signal transduction. Even, 5 root-to-shoot mRNA and 2 shoot-to-root mRNA were commonly present in 7 grafts that mainly involved in hormone transport and basic metabolism.   Conclusion  mRNA transfer in heterologous grafted plants is closely related to mRNA length, GC content, gene function and action position. mRNA differences and exchanges between heterologous plants give grafted plants new phenotypes.
Abstract:
  Objective  A regional-scale stand biomass growth model was established to provide methodological support for predicting the biomass and carbon storage of natural broadleaved forests in Guangdong Province of southern China in the future.   Method  Based on the five forest inventory data of Guangdong Province from 1997 to 2017, 203 natural forest sample plots with six broadleaved tree species such as Quercus spp., Schima superba and other soft broadleaved species as dominant tree species were selected. The site quality difference was reflected by parameter classification, the density effect was expressed by competition index, and the modeling method was distinguished by step-by-step modeling (univariate nonlinear regression method) and joint modeling (nonlinear simultaneous equations method). The DBH growth model, constructed by the theoretical growth equation, was used to estimate the stand age, and then various stand biomass growth models were constructed. The goodness of fit of the model was evaluated by four indexes such as determination coefficient and average prediction error. For the model with high goodness of fit, 183 sample plots by continuously inventory in four periods from 2002 to 2017 were taken as test samples, and the total relative error was used to verify its application effect.  Result  To compare the fitting effect and the estimation accuracy at regional scale and sample plot level for exploring the influence of four factors including stand density, different parameter classification, classification method and modeling method on the biomass growth model, it was found that nonlinear simultaneous equation was better than step-by-step modeling; the classification of model parameter b related to growth rate was better than that of model parameter a related to growth potential; considering the stand density and adding competition index to the hierarchical equation had little effect on optimizing model performance. Based on the classification of parameter b, the joint model without competition index in independent variable and the hierarchical equation was the optimal model, i.e. Model 10. The determination coefficient of the biomass growth model was 0.970 1. When Model 10 was used to predict the biomass of four periods, the prediction effect was good. But the estimation error in the later stage was significantly lower than that in the earlier stage. For example, when Model 10 was used to estimate the biomass of Quercus spp. at regional scale from 2002 to 2017, the estimation errors of four periods were 6.22%, 15.27%, 4.80% and −1.84%, respectively.   Conclusion  It is a feasible method to establish stand biomass growth model based on the Richards growth equation to estimate regional-scale biomass, which not only provides a basis for evaluating the carbon sink capacity of forest ecosystem at regional scale in a certain period in the future, but also provides a reference for the construction of stand biomass growth model in other regions.
Abstract:
  Objective  The effective of thinning is commonly evaluated by the growth dynamics of reserved trees. The stand diameter structure heterogeneity and growth dynamics of different tree species and diameter classes of spruce-fir mixed forest after thinning were studied in order to provide scientific guidance for operators to adjust thinning strategies.   Method  Based on four permanent sample plots of natural spruce-fir mixed forest in Jingouling Forest Farm of Jilin Province, northeastern China, which included one control sample plot and three thinning sample plots with different treatments (remove 21% (light), 27% (medium), 36% (heavy) of the basal area), we applied the concept of growth dominance (GD) with the Pressler growth rate and the Gini coefficient to analyze the dynamics of diameter structural heterogeneity and the growth feedback of different species and diameter classes after thinning.   Result  5 years after thinning, the growth rates of shade-tolerant tree species (light, medium and heavy) were 2.92%, 2.73% and 3.04%, respectively. The increase of thinning intensity had no significant promoting effect on shade-tolerant species but it can promote the growth of shade-intolerant tree species significantly (2.18%, 2.91%, 3.65%). The medium and light thinning intensity could improve the growth rates of small and medium diameter trees greatly but this impact is not obvious on the dominant trees, while heavy thinning had a strong positive effect on the growth of whole stand. The non-dominant trees of shade-intolerant species responded more positively to thinning, which had stronger negative growth dominance than shade-tolerant species. Thinning of medium-diameter trees can immediately improve the heterogeneity of stand structure. The Gini coefficient decreased after thinning showed that thinning can reduce the level of stand diameter structural heterogeneity by reducing the asymmetric competition and promoting the growth of small trees.   Conclusion  Heavy intensity thinning and regularly removing shade-tolerant dominant trees of weak contributors to stand growth can maximize stand productivity, while light thinning can promote the sustainable forest development, and accelerate the positive succession to the primary vegetation in northeastern China. The growth dominance can effectively reflect the growth status of trees in different diameter classes after thinning, and provide rational reference for thinning of trees.
Abstract:
  Objective  This paper aims to clarify the differences in the yield and economic benefits of three different management modes in varied specifications of diameter timber, as well as to provide reference for the economic feasibility of forest management projects and forest sustainable development.  Method  Taking the Pinus massoniana plantation in the Experimental Center of Tropical Forestry, Chinese Academy of Forestry Sciences as the research object, the observation data of the stand for 10 years (2008−2018) under the three management modes of near-natural transformation, conventional management (rotation operation) and control sample plot were selected. The wood values of large, medium and small diameter timber and the seedling value of replanted broadleaved trees were calculated by cash flow and replacement cost method, respectively. Dynamic economic indicators and sensitivity analysis method were used to evaluate the economic feasibility and risk tolerance of the three management modes, and the economic benefits of three management modes were comprehensively compared.  Result  There were obvious differences in the dynamic changes of wood structure of P. massoniana under the three management modes. From the 2nd to 10th year, the yield of large diameter timber increased from 1.22 to 56.85 m3, the yield of medium diameter timber increased from 23.34 to 79.57 m3, and the yield of small diameter timber decreased from 69.79 to 68.76 m3. In the mode of rotation management, yield of large diameter timber increased from 0.29 to 38.97 m3, the yield of medium diameter timber increased from 22.51 to 90.89 m3, the yield of small diameter timber decreased from 80.69 to 78.83 m3. In the mode of control management, the yield of large diameter timber increased from 0.25 to 27.97 m3, the yield of medium diameter timber increased from 20.95 to 93.69 m3, and the yield of small diameter timber decreased from 189.39 to 181.98 m3. During the past 10 years, the net profit (NP) under the three management modes of the near-naturalized transformed stand, the rotation management stand and the control all showed monotonous increasing trend, and the return on investment (ROI) of the three management modes showed a monotonous increasing trend, first increasing and then decreasing trend according to the above sequence. In the 10th year, the net present value of the near-naturalized transformed stand, the conventional management stand and the control were 594, 265, 193, respectively, the NP was 87 384.96, 85 745.21 and 71 935.09 CNY/ha, and the ROI was 8.02%, 7.92% and 5.95%, respectively. In the past 10 years, the seedling value of broadleaved tree species replanted under the crown continued to increase under the near-natural transformation mode, and the proportion of seedling value to stand economic income (W value) presented the trend of increasing-decreasing-increasing-decreasing. In the 4th−6th year, the fast-growing native tree species such as Quercus griffithii and Manglietia conifera reached the standard of medium and small diameter timber, and the W value decreased to 11.26%. In the 8th−10th year, as the Castanopsis hystrix, Erythrophleum fordii, Michelia hedyosperma and other precious tree species reached the standard of small diameter timber, the W value decreased again to 11.93%.  Conclusion  The P. massoniana plantation under three management modes are economically feasible investments. The initial cost of near-natural transformation is higher, but it is more conducive to cultivating large diameter timber, promoting the subsequent development and utilization of native precious and fast-growing species resources, and meeting the needs of different markets; the conventional management (rotation operation) tends to single tree species nurturing management, pursuing fast-growing and abundant production and relatively intensive management; the proportion of large diameter timber in the stand without management measures is lower, and natural regeneration is scarce, which is not conducive to the sustainable use of forest resources.
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  Objective  The green space next to the residence in the residential area is the green space closest to the residents’ life and used by the residents. It not only has ecological aesthetic value and health care function, but also can shield the low-rise residents’ space of the residence, and has certain safety. By constructing the quality evaluation index of green space beside urban residential area buildings, this study analyzed the influence of construction ages and green space types on the quality of green space beside residential buildings, aiming to provide theoretical support for the scientific construction of green space beside residential area buildings in the future.   Method  Taking green space beside residential area buildings with different construction ages in Beijing as the research object, the indicator system for quality evaluation of green space beside residential buildings was selected, and the indicator system was composed with tree species composition, spatial structure, aesthetic characteristics and plant health function. 9 of indicators were screened from 15 of primary indicators by correlation analysis. Three indices were constructed by dimensionality reduction using principal component analysis, and weights of the indices and indicators were determined by principal component analysis. Furthermore, the quality of green space beside residential area buildings in different construction ages was analyzed through the relationship between the index composite score and the selected indicators.   Result  (1) The quality of green space beside residential buildings was dominantly influenced by three main components, which were the three indices consisting of structure, tree species composition and aesthetics effect. And the influence degree of each index on spatial quality of the green space was 30.34%, 24.27% and 22.26%, respectively. (2) The integrated score of green space in intermediate residential areas was 1.60% and 8.34% higher than that of new residential area and old residential area, respectively, but the built ages of the residential areas had no significant effect on the quality of green space beside residential buildings. (3) The quality of green space beside buildings was significantly affected by green space type, and the integrated score from high to low was the combination between house pattern, natural community pattern, regular forest pattern and close-to-houses pattern. (4) The differences of spatial scale and plant configuration were main reasons for the quality difference among green space types.   Conclusion  The quality of green space beside residential area buildings is significantly affected by the type and structure, while it is not affected by the construction ages of the residential areas. The dominant factors which affect the quality of green space beside residential buildings are green space structure, spatial coordination degree and visual quality. Screened degree of view by plants and relative vertical green volume contribute greatly to the quality of green spatial structure; color richness and tree species diversity have positive effect on the quality of green space beside residential buildings; spatial coordination degree between vegetation and building has a positive impact on the green space quality within a certain range. Therefore, in the design and construction of residential green space, we should focus on the combination of buildings, natural group, regular forest of space types, less use or not close to the house. If the height of the residential building is certain, the width of the green space beside the house should be expanded appropriately, so as to ensure that the degree of space coordination is at a better level. What’s more, the proportion of the number of trees and shrubs is reasonably distributed in the near-natural composite planting structure, and on the basis of satisfying the spatial structure and function, it has both visual aesthetic feeling and landscape effect.
Abstract:
  Objective  This paper aims to clarify the status of surface fuel and corresponding fire behavior characteristics of pure Pinus yunnanensis stand under the conditions of periodic (burning cycle was 1 year) prescribed burning, and then explore the impact of prescribed burning on the fire behavior of surface fuel of P. yunnanensis, and reasonably evaluate the ecological significance of prescribed burning, so as to provide scientific basis for forest fire management and fighting.   Method  Sampling in field investigation and simulating combustion in laboratory, using the SPSS23.0 to process and analyze the data, we explored the influence of fuel types, fuel loads, moisture content and other characteristics of prescribed burning on fire behavior such as the temperature of fire, flame height, thermal radiation, spread rate, burning rate, fire intensity, etc. in Zhaobi Mountain, Xinping County, Yuxi City, Yunnan Province of southwestern China.  Result  (1) The main fuel on the surface of pure P. yunnanensis stand was the withered pine needles, plus a small amount of withered pine branches and cones and dead ferns, the species was relatively single, and most of the fuel under the forest was fine fuel. (2) From 2018 to 2020, the average moisture content of dead fuel under the pure forest of P. yunnanensis was 9.39%, 8.04% and 9.89%, and the average fuel loads were (0.937 ± 0.303) kg/m2, (0.926 ± 0.253) kg/m2 and (0.669 ± 0.248) kg/m2, respectively. (3) The simulated fire behavior in the laboratory included: the fire intensity was (245.95 ± 130.51) kW/m, the flame height was (0.92 ± 0.22) m, fire ground temperature was (437.5 ± 171.6) ℃, the thermal radiation was (6.3 ± 0.9) kW/m2, the spread rate was (1.1 ± 0.3) m/min, the ignition time of the surface fuel was 1 s and burning rate was about 62%. (4) The mortality of P. yunnanensis in natural state was about 1.33%. In the field survey in 2018 and 2020, the mortality of P. yunnanensis under prescribed burning was 0.93% and 1.27%, respectively. P. yunnanensis has certain fire resistance.  Conclusion  (1) For the pure P. yunnanensis stand under periodic prescribed burning, the canopy density of the standing forest is large, and the combustible vegetation under the forest is less, mainly pine needle litter and grass. (2) Prescribed burning can effectively reduce the surface fuel load, and the average load of surface fuel is less than 1 kg/m2. During the fire prevention period, the moisture content of the dead fuel on the surface of P. yunnanensis forest is less than 10%, which is easy to be ignited, but the flame height is within the range of 0.5−1.5 m, and the fire intensity is less than 750 kW/m, which belongs to low intensity fire; the temperature of the fire ground is high, the thermal radiation is strong, the fire spread speed is general, and the fire field can be controlled; the simulated burning rate in the laboratory is high, and the combustion effect is good. (3) It is necessary and feasible to carry out periodic prescribed burning in fire prone habitats and forests with certain adaptability to fire.
Abstract:
  Objective  Land use change is an important factor leading to changes in ecosystem services and their relationships. It is significant to explore the impact of land use on ecosystem services.  Method  This study is based on the land use data of Tianjin in 2000 and 2015, combined with regional development planning, using the GeoSOS-FLUS model to predict the land use structure under three different situations in 2030, and using the InVEST model to evaluate ecosystem services and trade-offs.  Result  (1) From 2015 to 2030, under the business as usual, cities continued to expand, construction land increased by 27.68%, and cultivated land decreased by 11.47%. Under the ecological planning, urban expansion slowed down, construction land increased by 7.97%, and woodland, grassland, waters and shrubs increased by 2.02%. Under the rapid urban development, construction land and cultivated land remained stable, and the water area increased by 4.78%. (2) From 2015 to 2030, the comprehensive ecosystem service index of Tianjin under different situations showed a downward trend. In 2030, the total ecosystem service indexes of business as usual, ecological planning and rapid urban development were 0.172, 0.181 and 0.180, respectively. (3) From 2015 to 2030, the direction of the synergy of the four ecosystem services under different situations had not changed, but the strengths and weaknesses had undergone complicated changes. In general, the synergy relationship was stronger under the ecological planning and weaker under the business as usual.  Conclusion  This study suggests that Tianjin City should slow the urban expansion, optimize the current land use structure, and enhance the ecological environment construction in the future. The research results can provide a theoretical basis of ecosystem management in Tianjin.
Abstract:
  Objective  This paper aims to analyze the variation of soil microbial community structure characteristics of larch plantation at different plantation ages, clarify the response mechanism of soil microbial community structure to the changes of plantation age and its key influencing factors, provide theoretical basis for sustainable management of the plantation and feedback effect of soil microbial community to environmental changes.  Method  Based on the characteristics of soil microbial community structure, soil physical and chemical properties and understory vegetation characteristics database, this study explored the regulation mechanism of soil physical and chemical properties and understory vegetation characteristics on the formation of soil microbial communities by redundancy analysis.  Result  The change of plantation age had a significant impact on soil physical and chemical properties and microbial community structure, such as soil temperature, water content, pH, total carbon, total nitrogen, total phosphorus, ammonium nitrogen and nitrate nitrogen content increased significantly with the increase of plantation age, but the soil available phosphorus content showed the opposite trend (P < 0.05). Meanwhile, the growth of the plantation age also significantly increased the abundance of gram-positive bacteria, gram-negative bacteria, fungi and actinomycetes in the soil, while the ratio of fungi: bacteria and gram-positive bacteria: gram-negative bacteria showed a downward trend. The diversity of understory shrubs and herb layers also showed a trend of increasing with the increase of forest age, and the differences between different forest ages did not reach a significant level. The results of redundant analysis showed that the soil physical and chemical properties and the understory vegetation diversity index explained 86.1% of the total variation of the soil microbial community, while the soil water content, soil temperature, available phosphorus, nitrate nitrogen content, and the richness index of shrub and herb layer explained 22.7%, 18.4%, 11.8%, 10.6%, 7.9% and 5.6% of the variation of microbial community structure, respectively.   Conclusion  The structural characteristics of soil microbial community, soil physical and chemical properties, and understory plant diversity (ie shrub layer and herb layer) are all affected by changes of plantation age. Notably, soil temperature, water content, available phosphorus, nitrate nitrogen, and understory vegetation diversity are key factors to drive the changes of soil microbial community structure in different plantation ages.
Abstract:
  Objective  This paper aims to study the key evaluation indexes of soil anti-erodibility of Robinia pseudoacacia forest (16 years), and discuss the effects of stand density on soil anti-erodibility in the loess region of western Shanxi Province of northern China, which could provide functional guidance for the precise improvement of stand structure.   Method  The research objects were five density gradients (1 025, 1 300, 1 575, 1 800, 2 150 tree/ha) of R. pseudoacacia forest. Based on field sampling and laboratory tests, 12 indexes about soil anti-erodibility had been analyzed.   Result  (1) Principal component analysis showed that the soil bulk density, organic matter, > 0.25 mm water-stable aggregate, mean mass diameter, geometric mean diameter, fractal dimension and soil dispersion coefficient were key indexes to evaluate soil anti-erodibility of R. pseudoacacia forest, these factor loads were −0.776, 0.864, 0.747, 0.960, 0.779, −0.736 and −0.873, respectively. (2) Anti-erodibility of surface soil of R. pseudoacacia forest was stronger than that of deep soil under the same stand density, the comprehensive index of soil anti-erodibility: 0−10 cm (0.548) > 10−20 cm (−0.070) > 20−30 cm (−0.477). In the same soil layer, soil anti-erodibility increased with the increase of stand density (1 025−1 575 tree/ha) of R. pseudoacacia forest, and decreased when the stand density was higher than 1 575 tree/ha. (3) Taking the stand density of R. pseudoacacia forest as the x-axis and the comprehensive index of soil anti-erodibility as the y-axis, the parabolic function relationship with opening downward was established: y = −2.683 × 10−6x2 + 0.009x − 6.375 (R2 = 0.77), soil anti-erodibility was the strongest when the stand density of R. pseudoacacia was 1 590 tree/ha, and the comprehensive index was 0.403.  Conclusion  Soil anti-erodibility of medium density R. pseudoacacia forest is strong. From the perspective of soil anti-erodibility, the management density of R. pseudoacacia forest (16 years) should be 1 590 tree/ha in the loess region of western Shanxi Province. For the stand with too low or too high density, scientific replanting or thinning should be carried out in time while meeting the forestry production. Attention should also be paid to the protection of topsoil, so as to give full play to the water and soil conservation function of forest land and effectively control soil erosion.
Horticulture Sciences
Abstract:
  Objective  Color is the major ornamental characteristics of plants, anthocyanins are the key compounds of flower colors. The types and contents of anthocyanins can provide insight into the mechanism of petal color.  Method  In this study, 36 samples of three pairs of Rhododendron subgenus Tsutsusi parents and their hybrids were subjected to anthocyanins profiling in petals and their separation characteristics using UPLC –Q –TOF –MS.   Result  This study identified 17 compounds, including peonindin 3-O-galactoside, delphinidin 3-galactoside, malvidin 3-O-galactoside, and petunidin 3-galactoside, which were detected for the first time in Rhododendron subgenus Tsutsusi. A majority of anthocyanins in Rhododendron subgenus Tsutsusi are cyanidin, peonidin, and petunidin in the form of arabinosides. Cyanidin 3-arabinoside, cyanidin 3-O-glucoside and peonidin are responsible for the red-colored petals in Rhododendron subgenus Tsutsusi. Delphinidin 3-arabinoside, delphinidin 3-O-glucoside, malvidin 3-arabinoside, and malvidin 3-O-glucoside contribute to the petal’s purple color, while petunidin 3-O-arabinoside contributes to their purplish red color. The anthocyanin segregation analysis revealed that peonidin and cyanidin had transgressive inheritance, whereas malvidin 3-arabinoside, malvidin 3-O-glucoside, and petunidin 3-O-arabinoside had paternal inheritance.   Conclusion  In this study, we demonstrate the coloring mechanism of Rhododendron subgenus Tsutsusi, which provides a reference for parent selection in breeding.
Landscape Architecture
Abstract:
  Objective  In order to explore the feasibility and economy of urban park green space sponge city construction in semi humid area and provide economic decision-making reference for designers and decision makers, this paper takes the cost-effectiveness of rainwater runoff collection and irrigation as the research content, and takes the built rainwater collection green space on Binhu East Road, Qian’an City, Hebei Province of northern China as the research object to study the cost of rainwater collection and irrigation of park green space in semi humid area.  Method  The volume of rainwater storage tank was determined according to the site runoff. Based on the daily measured rainfall data from 2014 to 2021 and the predicted rainfall data from 2022 to 2024, the volume method was used to calculate the annual collected runoff. The cost savings were obtained by comparing the cost of green land irrigation with tap water and the cost of irrigation with collected runoff and tap water, and the construction benefits were obtained by comparing the construction cost and maintenance cost.   Result  Based on the actual rainfall data from 2014 to 2021, the predicted rainfall data from 2022 to 2024 and the calculation of construction cost, when the catchment area was 155.37 ha and the irrigation area was 151.410 ha, for the purpose of solving runoff and from the perspective of long-term benefits, the best scheme for the scale of regulating and storage tank was 3 000 m3, and the average annual irrigation cost was 101114.15 CNY, the average annual benefit was 65 424.15 CNY.   Conclusion  Runoff collection and irrigation utilization in semi humid areas has certain benefits. Taking the irrigation demand of plants in a certain period of time as the standard of runoff collection can significantly reduce the construction cost and increase the runoff utilization efficiency.
Forestry Engineering
Abstract:
  Objective  In order to provide basis for the application of melamine-urea-glucose (MUG) composite modifier and promote wood green modification, the changes of micro morphology, chemical structure and element composition of modified wood were studied, and the modification mechanism of biomass resin compound modifier on wood was discussed.   Method  By introducing hydrophobic groups such as organosilane into the compound solution of MUG biomass resin and sodium silicate, the silane hybrid modifier (GST) was prepared. Then the poplar wood was modified with it by vacuum pressure impregnating treatment. The physical and mechanical properties of modified wood were tested. Its micro-morphology, chemical structure, element composition and crystallinity were characterized by scanning electron microscopy-energy dispersive X-ray spectrometer (SEM-EDX), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD). The combustion performance and pyrolysis characteristics were tested by micro calorimeter (MCC).   Result  SEM-EDX analysis showed that GST modifier had good permeability and can effectively penetrate into wood cell cavity and cell wall; the C, O and Si element of modified wood were irregularly distributed in wood cell cavity, cell wall and cell gap, and the modifier was most deposited in wood vessels. Due to the effective filling of wood pores and the swelling of cellulose amorphous zone, wood dimensional stability and mechanical properties were improved. FTIR analysis showed that hemicellulose and other polysaccharides in GST modified wood had a cross-linking reaction with the modifier, reducing C=O, —OH and other hydroscopic groups. XPS analysis found that the C1 of GST modified wood was the most and its C3 was the least. During the modification process, the active groups such as polysaccharides, lignin alcohol hydroxyl, phenol hydroxyl and carbonyl reacted with the modifier, reducing the active groups and increasing the contents of C—H and C—C structure. XRD analysis showed that the diffraction peaks of the GST modified wood had no obvious change, its relative crystallinity increased, indicating that the modifier entered the amorphous region of cellulose to make its molecular arrangement more orderly. MCC analysis showed that the heat release capacity, peak heat release rate and total heat release of GST modified wood decreased by 65.7%, 66.2% and 6.2%, respectively, the residual carbon rate at 800 ℃ increased by 122.6%, its heat release intensity was greatly reduced and its fire risk was reduced.   Conclusion  GST compound modifier can effectively penetrate into poplar wood, cross-linked with its hemicellulose and other polysaccharides, reduce active groups such as sugar groups, and make the arrangement of amorphous regions more orderly, so as to improve its physical and mechanical properties.
Abstract:
  Objective  The structure of the Guzheng soundboard is one of the important factors affecting its vibration performance. The sound quality and tone color of the soundboards with different structures will be different. So far few scholars have studied the vibration and sound characteristics of the common structure of the composite Guzheng soundboard.  Method  In this study, two modal analysis methods were used to investigate the acoustic vibration performance of the composite soundboard. The experimental modal analysis method was used to analyze the collected excitation signal and the vibration response signal using digital signal processing technology. After data conversion, the frequency response function of the system was obtained, and then the resonance frequencies of each order and the corresponding modal shapes were obtained. Through using computational modal analysis, a three-dimensional model of the composite soundboard was established, discreting it by finite element method, then the resonance frequencies of each order and the corresponding mode shapes were calculated by approximate method.   Result  The experimental modal results showed that the (0, n) and (1, n) orders could be identified and they were mostly concentrated in (0, n). The (1, 4), (1, 6), (1, 7) and (1, 10) order were composite vibrations that bending along grain and perpendicular grain directions, and they were more difficult to identify. The modal shapes of the composite soundboard corresponding to each order frequency were clear and easy to identify. Compared with the experimental results, the computational modal analysis could identify all orders in the selected order range, and the modal shapes were more uniform and ideal. However, it was difficult to identify individual orders in the experimental modal analysis. The results of computational modal analysis showed significant linear correlation with the experimental modal results, and the correlation coefficient was 0.9996.   Conclusion  From the results of modal analysis, the modal shapes of the composite soundboard corresponding to each order frequency are easier and more clear to identify than the whole soundboard, and the vibration frequency is also higher. In terms of wood utilization, the composite soundboard is more conducive to saving wood resources than making the whole soundboard. Through the comprehensive comparison of the two kinds of modal analysis results, it is verified that the computational modal analysis is feasible to apply to the vibration modal analysis of the Guzheng soundboard.
Abstract:
  Objective  The polymer composite material made from lignin can improve the high additional utilization value of renewable lignin resources. If lignin is introduced into the hydrogel, not only the effective substitution of fossil raw materials in the hydrogel can be realized, but also the strength of the hydrogel can be improved, and the hydrogel can be given a variety of excellent properties.   Method  Under alkaline conditions, a multifunctional sodium lignosulfonate@tannic acid-polyacrylic acid (TA@SL-PAA) hydrogel was produced using sodium lignosulfonate and tannic acid as raw materials and ammonium persulfate as initiator through in-situ reduction of Fe3+. It was proved by infrared spectrometer and scanning electron microscope that sodium lignosulfonate was successfully coated on the surface of tannic acid. Properties such as electrical conductivity, electrical conductivity, and self-healing properties were investigated.   Result  Tannic acid was successfully loaded on sodium lignosulfonate to form a sodium lignosulfonate@tannic acid (TA@SL) complex. The sodium lignosulfonate@tannic acid hydrogel prepared from TA@SL had good mechanical properties. Under the best conditions, its elongation at break can reach 1 700%, and its compressive strength can reach 275 kPa. The hydrogel has high transparency and effective UV shielding effect, and the UV absorption capacity can reach 100%. In addition, due to the presence of sodium lignosulfonate and metal ions, the hydrogel also has excellent adhesion, self-healing ability, electrical conductivity and high sensitivity. It is worth mentioning that using the sensing properties of the hydrogel to prepare hydrogel electrodes can effectively capture stable electromyogram and electrocardiogram signal.   Conclusion  Due to the good mechanical properties, electrical conductivity, and self-healing properties of sodium lignosulfonate@tannin hydrogels, it has great potential for applications in sensors, commercial electrodes, and wearable electrodes.
Abstract:
  Objective  The solid shell of Quercus mongolica is rich in polyphenols, flavonoids and other active compounds with a variety of functions. In order to further develop Q. mongolica resources and obtain high antioxidant activity and efficient preparation methods, the active components and antioxidant activity of Q. mongolica shell extracts extracted by different methods were compared.   Method  The contents of total phenols, total flavonoids, total triterpenoids and soluble sugar were determined by spectrophotometry. Fourier transform infrared spectroscopy (FTIR) was used to analyze the functional group changes of the extracts of Q. mongolica with 4 extraction methods.   Result  There were significant differences in the effects of the four extraction methods on the extraction efficiency and antioxidant activity of Q. mongolica shell, among which enzymatic hydrolysis method had the best extraction effect on phenolic compounds from Q. mongolica shell, and the total phenolic content per 100 g was as high as (1.090 ± 0.570) g. FTIR showed that the absorption peak intensity was the highest at 3401 and 1 039 cm−1, which were the stretching vibration of hydroxyl O−H and C−O−C of phenolic substances, respectively. In vitro antioxidant test results showed that the antioxidant activity of the extract was the strongest. When the concentration of the extract solution was 0.80 g/L, the scavenging rate of ·OH was 98.55%, which was higher than that of VC (82.03%). Correlation analysis showed that polyphenols played a major role in antioxidant activity.   Conclusion  The active components and antioxidant capacity of extracts extracted by solvent extraction, high shear method, ultrasonic method and enzymatic hydrolysis method were compared. It is found that enzymatic hydrolysis method has the highest content of active substances and antioxidant activity. Therefore, the enzymatic hydrolysis method is an effective method to extract rich antioxidant active substances from Q. mongolica shell, and the enzymatic hydrolysis extraction is simple, low cost, which can be used for the preparation of active substances and natural antioxidant development of Q. mongolica shell. The results of this study provide theoretical basis for the selection of extraction technology of Q. mongolica shell extract and the development and utilization of antioxidants.

Establishment Time:1979

CN 11-1932/S

ISSN 1000-1522

Supervisor:Sinopec Research Institute of Petroleum Engineering

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