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东北地区夏季骤旱下植被响应与恢复特征及其影响因素

Characteristics of Vegetation Response and Recovery and its Influencing Factors Under Summer Flash Drought in Northeast China

  • 摘要: 全球变暖背景下,水循环加速,骤旱频发,进而对陆地生态系统产生重要的影响;但是,目前关于中国东北地区植被对骤旱的响应与恢复方面的研究还相对有限。本文基于ERA5-Land土壤湿度数据筛选骤旱事件,首先对2000-2022年东北地区夏季骤旱事件进行了识别,分析了其发展与恢复阶段的空间分布特征。在此基础上,结合MODIS叶面积指数(Leaf Area Index,LAI)分析了不同植被类型对骤旱响应与恢复阶段的特征差异,进一步采用随机森林与偏相关分析方法,探讨了其主导因素的空间格局。结果表明,东北地区不同植被类型对骤旱的响应和恢复存在明显差异。具体而言,森林在响应阶段的时间最长(28天),但恢复时间最短(12天)。相较之下,草地在响应阶段的时间最短(10天),但恢复时间最长(30天)。此外,森林的下降速率和恢复速率均较快,分别为0.99/候和1.02/候,而草地则表现为较慢的下降和恢复速率,为0.31/候和0.41/候。主导因素分析结果表明,土壤湿度和饱和水汽压差(Vapor Pressure Deficit,VPD)是影响植被响应时间的主要因素,骤旱发展速率和气温对植被的下降速率起主要作用,植被恢复时间主要受土壤湿度和降水影响,而恢复速率主要受土壤湿度和VPD影响。气温和VPD分别决定了50%以上森林的下降速率及恢复速率,且均高于草地和农田,土壤湿度主导了超过73%的森林、草地、农田的响应时间和恢复时间。研究结果可在一定程度上为骤旱对不同生态系统的可能影响提供一定的参考,同时加深对骤旱发生后生态系统的响应与恢复的理解。

     

    Abstract: Global warming has led to the intensification of the water cycle and the frequent occurrence of flash drought, which in turn has an important impact on the terrestrial ecosystem. However, the research on the response and recovery of vegetation to flash drought in Northeast China is relatively limited. This paper uses soil moisture which from ERA5-Land reanalysis data to select flash drought events and identify the summer flash drought in Northeast China from 2000 to 2022 firstly, and the spatial distribution characteristics during onset and recovery stages are analyzed. On this basis, the characteristics of different vegetation types response and recovery to flash drought are analyzed by combining with the MODIS Leaf Area Index (LAI), and the spatial pattern of dominant factors is further discussed by using random forest model and partial correlation analysis. The results show that there are significant differences in response and recovery of different vegetation types to flash drought in Northeast China. Specifically, forest has the longest response time (28 days) but the shortest recovery time (12 days), while grasslands has the shortest response time (10 days) but the longest recovery time (30 days). In addition, the decrease and recovery rate of forests are both faster (0.99/pentads and 1.02/pentads), while that of grasslands are slower (0.31/pentads and 0.41/pentads). The results of dominant factors suggest that soil moisture and Vapor Pressure Deficit (VPD) are the main factors affecting the response time of vegetation, the onset rate of flash drought and temperature play a major role in the decrease rate, the recovery time of vegetation is mainly impacted by soil moisture and precipitation, and the recovery rate is primarily influenced by soil moisture and VPD. Moreover, temperature and VPD determined the decrease and recovery rate of more than 50% of forests, respectively, and are higher than that of grasslands and croplands, while soil moisture dominates the response and recovery time of more than 73% of forests, grasslands and croplands. This paper results can provide some reference for the possible effects of flash drought on different ecosystems, and deepen the understanding of ecosystem response and recovery after flash drought.

     

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