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    马雅莉, 郭素娟. 板栗冠层光合特性的空间异质性研究[J]. 北京林业大学学报, 2020, 42(10): 71-83. DOI: 10.12171/j.1000-1522.20200059
    引用本文: 马雅莉, 郭素娟. 板栗冠层光合特性的空间异质性研究[J]. 北京林业大学学报, 2020, 42(10): 71-83. DOI: 10.12171/j.1000-1522.20200059
    Ma Yali, Guo Sujuan. Spatial heterogeneity of photosynthetic characteristics in Chinese chestnut canopy[J]. Journal of Beijing Forestry University, 2020, 42(10): 71-83. DOI: 10.12171/j.1000-1522.20200059
    Citation: Ma Yali, Guo Sujuan. Spatial heterogeneity of photosynthetic characteristics in Chinese chestnut canopy[J]. Journal of Beijing Forestry University, 2020, 42(10): 71-83. DOI: 10.12171/j.1000-1522.20200059

    板栗冠层光合特性的空间异质性研究

    Spatial heterogeneity of photosynthetic characteristics in Chinese chestnut canopy

    • 摘要:
        目的  冠层是林木与外部环境相互作用的重要部分,研究板栗树冠不同部位光合作用的空间变化规律,为揭示植物冠层生产力提供理论依据。
        方法  以8年生板栗树为试验材料,采用Li-6400便携式光合作用测量系统,于7月对板栗树冠不同冠层和不同方位进行光合日变化测定,并取光合参数的日均值进行方差分析及通径分析,于9月对不同冠层和不同方位的刺苞进行采集,测定坚果经济性状,并进行方差分析及相关性分析。
        结果  (1)东上、东中、南中及南下冠层的净光合速率日变化呈单峰曲线分布,其余部位均表现为双峰曲线,呈双峰曲线分布的区域均于13:00出现“午休”现象;每一冠层区域的水分利用效率日动态均呈双峰曲线。(2)在冠层垂直方向上,水汽压亏缺及胞间CO2浓度均呈“下部 > 中部 > 上部”的规律,其最大值分别为2.13 kPa、274.93 μmol/mol,最小值分别为1.95 kPa、258.75 μmol/mol;光合速率、气孔导度、蒸腾速率、光合有效辐射、水分利用效率及羧化效率均呈“上部 > 中部 > 下部”的规律,同时,相对叶绿素含量(SPAD)和比叶面积(SLA)在垂直冠层上均有显著差异,表现为“下层 > 中层 > 上层”的规律。(3)在树冠不同方位,东面光合能力最强,各冠层光合生理生态指标有一定差异性,但无垂直方向差异显著;SLA在不同方位无显著差异,仅SPAD在东西向与北向差异显著。(4)通径分析得出,影响板栗净光合速率的主要因子为蒸腾速率、水分利用效率、羧化效率、水汽压亏缺、气孔导度、气温及胞间CO2浓度,其中,只有气温对净光合速率起抑制作用,蒸腾速率是对板栗光合作用影响最大的生理因子,水汽压亏缺是对板栗光合作用影响最大的环境因子。(5)垂直冠层上,净光合速率与单粒质量、出实率和单位面积产量均呈显著或极显著正相关,相关系数分别为0.872、0.965、0.958;水平冠层上,净光合速率与单粒质量、单位面积产量呈显著正相关,相关系数分别为0.777、0.487;对水平和垂直冠层进行综合分析发现,净光合速率与单粒质量、出实率、单位面积产量均呈显著或极显著正相关关系,相关系数分别为0.600、0.669与0.532。
        结论  板栗光合具有明显的空间异质性,各光合指标与果实产量的差异性是垂直冠层和水平冠层综合作用的结果。因此,在估算冠层生产力时,应充分考虑到冠层光合作用的垂直变化和水平变化,在实际生产中,应合理修枝,提高冠层中下部的光能利用率,从而促进果实产量的提高。

       

      Abstract:
        Objective  Canopy is an important part of the interaction between trees and external environment. The study on spatial variation law of photosynthesis in different parts of Chinese chestnut canopy provides a theoretical basis for revealing Chinese chestnut canopy productivity.
        Method  The 8-year-old Chinese chestnut trees were used as tested materials, the Li-6400 portable photosynthesis measurement system was used to determine the diurnal changes of photosynthesis in different canopies and positions of the Chinese chestnut canopy in July, fruit collection was carried out to determine the economic traits of nuts in September. Variance analysis, path analysis and regression analysis were done on the base of indexes.
        Result  (1) The daily dynamics of photosynthetic rate (Pn) in the upper east, middle east, south middle, and lower south showed a unimodal curve distribution; the rest of the region showed a bimodal curve, and the areas showing a bimodal curve distribution all presented a “midday depression” phenomenon at 13:00. The daily dynamics of water use efficiency (WUE) in each canopy area presented a bimodal curve. (2) In the vertical direction of the canopy, the deficient vapor pressure (VpdL) and intercellular CO2 concentration (Ci) were shown as “lower > middle > upper”. The maximum values were 2.13 kPa, 274.93 μmol/mol, and the minimum values were 1.95 kPa, 258.75 μmol/mol; photosynthetic rate, stomatal conductance (Gs), transpiration rate (Tr), photosynthetically active radiation (PAR), WUE and carboxylation efficiency (Vc) presented a “upper > middle > lower” phenomenon. The SPAD and specific leaf area (SLA) had significant differences in the vertical canopy (P < 0.05), and both showed “lower > middle > upper”. (3) In different directions in the canopy, the strongest photosynthetic capacity was in the east, but the photosynthetic indexes were not significantly different compared with the vertical canopy. The SPAD only had significantly difference in the east, west and north directions. The SLA was not significantly different in varied directions. (4) Path analysis showed that the main factors affecting Pn were Tr, WUE, Vc, VpdL, Gs, air temperature (Ta) and Ci, only Ta had an inhibitory effect on the Pn; Tr and VpdL were the physiological and environmental factors that had the greatest influence on Chinese chestnut photosynthesis.(5)In the vertical canopy, the Pn was significantly or extremely significantly and positively correlated with the single fruit mass, bur nut rate and yield per unit area, and the correlation coefficients were 0.872, 0.965 and 0.958, respectively. In the horizontal canopy, the Pn was significantly positively correlated with the single fruit mass and yield per unit area, and the correlation coefficients were 0.777 and 0.487, respectively. A comprehensive analysis of the horizontal and vertical canopy showed that the Pn was significantly or extremely significantly and positively correlated with the single fruit mass, bur nut rate and yield per unit area, with correlation coefficients of 0.600, 0.669 and 0.532, respectively.
        Conclusion  The photosynthesis of Chinese chestnut has obvious spatial heterogeneity, and the difference between photosynthetic index and fruit yield is the result of synthesis of vertical and horizontal canopy. In Chinese chestnut production, pruning should be reasonable to improve the efficiency for solar energy utilization in the lower and middle part of canopy, so as to increase the fruit yield.

       

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