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    张峰源, 苏远航, 刘滨辉. 东北森林生长季NDVI对昼夜不对称增温及降水变化的响应特征[J]. 北京林业大学学报, 2023, 45(2): 34-48. DOI: 10.12171/j.1000-1522.20210396
    引用本文: 张峰源, 苏远航, 刘滨辉. 东北森林生长季NDVI对昼夜不对称增温及降水变化的响应特征[J]. 北京林业大学学报, 2023, 45(2): 34-48. DOI: 10.12171/j.1000-1522.20210396
    Zhang Fengyuan, Su Yuanhang, Liu Binhui. Response characteristics of NDVI to asymmetric diurnal temperature increase and precipitation changes during the forest growing season in Northeast China[J]. Journal of Beijing Forestry University, 2023, 45(2): 34-48. DOI: 10.12171/j.1000-1522.20210396
    Citation: Zhang Fengyuan, Su Yuanhang, Liu Binhui. Response characteristics of NDVI to asymmetric diurnal temperature increase and precipitation changes during the forest growing season in Northeast China[J]. Journal of Beijing Forestry University, 2023, 45(2): 34-48. DOI: 10.12171/j.1000-1522.20210396

    东北森林生长季NDVI对昼夜不对称增温及降水变化的响应特征

    Response characteristics of NDVI to asymmetric diurnal temperature increase and precipitation changes during the forest growing season in Northeast China

    • 摘要:
        目的  东北地区森林面积广袤,是我国重要的生态屏障。本文旨在研究昼夜不对称增温的背景下,东北森林生长季NDVI变化及其对气候的响应,以期为东北地区林业建设与保护提供科学数据与指导。
        方法  基于2000—2019年SPOT Vegetation NDVI数据、植被类型空间分布数据以及逐月降水、气温数据,应用趋势分析、Hurst指数、相关分析等方法,探究昼夜不对称增温的背景下东北森林生长季NDVI的时空演变规律,对气候因子的响应特征及未来变化趋势。
        结果  (1)近20年东北森林生长季NDVI整体呈上升趋势,每10年增加0.035,其中混交林增加趋势最大,每10年增加0.037,阔叶林最小。东北森林以改善为主,占总面积55.59%,另有43.84%的森林保持基本不变,仅有0.57%的区域森林属于退化状态。(2)从整个生长季来看,NDVI受最低气温和降水影响显著,与最高气温关系不密切,同时生长季最低气温和降水呈明显增加趋势,最高气温无明显变化,一定程度上解释了在昼夜不对称增温的背景下,东北森林生长季NDVI增加;不同林型对气候响应不完全相同:3种森林类型中,针叶林生长主要受最低气温影响,阔叶林生长由降水和最低气温共同控制,混交林生长对降水最为敏感。(3)从逐月特征来看,生长季前期(4—5月)NDVI主要受最高气温和最低气温共同影响,旺盛生长期(6—8月)对降水敏感性较高,生长季末期(9—10月)受最低气温和降水共同控制;NDVI对降水、温度敏感性均呈现明显的时滞性特征。(4)利用Hurst指数对未来趋势进行分析,显示东北森林将由改善转为退化,有71.94%的森林将面临退化风险,尤其是中部和北部气候变化剧烈区域。
        结论  白天和夜晚升温的不对称性和NDVI对最高、最低气温差异性响应特征,导致白天和夜晚温度对东北森林NDVI近20 年变化具有不对称影响;2000—2019年东北森林生长季NDVI呈增加趋势,但未来面临退化风险。

       

      Abstract:
        Objective  The vast forest zone in Northeast China is an important ecological barrier of China. In this paper, changes of growing season NDVI and its response to climate change for forest in Northeast China (northeast forest) was studied in order to provide scientific basis and guidance for forestry establishment and protection in this region under the background of diurnal asymmetric warming.
        Method  Based on the SPOT Vegetation NDVI, different vegetation types’ spatial distribution, monthly precipitation and monthly temperature data from 2000 to 2019, using trend analysis, Hurst index and coefficient correlation analysis method, this paper investigates the spatial and temporal changing characteristics of growing season NDVI and its response to climate change for forest in Northeast China under the background diurnal asymmetric increase.
        Result  (1)In recent 20 years, growing season NDVI for forest in Northeast China generally showed an increasing trend, with the growth rate of 0.035 per ten years. The mixed forest showed the highest increase rate, reached 0.037 per ten years, the broadleaved forest showed the smallest increase rate. Northeast forests are mainly improved, accounting for 55.59% of the total area. Another 43.84% of the forests remained basically unchanged, and only 0.57% of the regional forests were degraded. (2)For the whole growing season, NDVI was significantly affected by minimum temperature and precipitation, and was weakly related to maximum temperature, at the same time, minimum temperature and precipitation in the growing season showed an obvious increasing trend, and maximum temperature had no obvious change, which contributed the increase of NDVI in northeast forest during growing season obviously under the background of diurnal asymmetric warming. Different forest types had varied responses characteristics: among the three forest types, coniferous forest growth was mainly affected by minimum temperature; broadleaved forest growth was mainly affected by precipitation and minimum temperature; mixed forest growth was most sensitive to precipitation. (3)For the monthly response characteristics, the NDVI in the early growing season (from April to May) was mainly affected by the maximum temperature and the minimum temperature, and the temperature sensitivity decreased gradually with the increase of temperature. At the end of the growing season (from September to October), it was jointly controlled by the minimum temperature and precipitation, and the precipitation sensitivity was higher in the mid growing season (from June to August). The sensitivity of NDVI to precipitation and temperature showed obvious time lag characteristics. (4) Future trend analysis indicated that the forest in Northeast China will change from improvement to degradation, around 71.94% of all forest will at risk of degradation, especially in areas with severe climate change regions.
        Conclusion  Diurnal asymmetric warming and differential response of NDVI to the maximum and minimum temperature lead to the asymmetric effect of daytime and nighttime temperature on the change of NDVI for forest in Northeast China. From 2000 to 2019, the growing season NDVI for forest in Northeast China has been increasing, but will be at risk of degradation in future.

       

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