Institute of Carbon Neutrality, Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, China.
Glob Chang Biol. 2024 Jan;30(1):e16998. doi: 10.1111/gcb.16998. Epub 2023 Oct 29.
Identifying droughts and accurately evaluating drought impacts on vegetation growth are crucial to understanding the terrestrial carbon balance across China. However, few studies have identified the critical drought thresholds that impact China's vegetation growth, leading to large uncertainty in assessing the ecological consequences of droughts. In this study, we utilize gridded surface soil moisture data and satellite-observed normalized difference vegetation index (NDVI) to assess vegetation response to droughts in China during 2001-2018. Based on the nonlinear relationship between changing drought stress and the coincident anomalies of NDVI during the growing season, we derive the spatial patterns of satellite-based drought thresholds (T ) that impact vegetation growth in China via a framework for detecting drought thresholds combining the methods of feature extraction, coincidence analysis, and piecewise linear regression. The T values represent percentile-based drought threshold levels, with smaller T values corresponding to more negative anomalies of soil moisture. On average, T is at the 8.7th percentile and detectable in 64.4% of China's vegetated lands, with lower values in North China and Jianghan Plain and higher values in the Inner Mongolia Plateau. Furthermore, T for forests is commonly lower than that for grasslands. We also find that agricultural irrigation modifies the drought thresholds for croplands in the Sichuan Basin. For future projections, Earth System Models predict that more regions in China will face an increasing risk for ecological drought, and the Hexi Corridor-Hetao Plain and Shandong Peninsula will become hotspots of ecological drought. This study has important implications for accurately evaluating the impacts of drought on vegetation growth in China and provides a scientific reference for the effective ecomanagement of China's terrestrial ecosystems.
识别干旱并准确评估干旱对植被生长的影响，对于理解中国陆地碳平衡至关重要。然而，很少有研究确定影响中国植被生长的关键干旱阈值，这导致在评估干旱的生态后果方面存在很大的不确定性。在本研究中，我们利用网格化地表土壤湿度数据和卫星观测的归一化差异植被指数（NDVI）来评估 2001-2018 年期间中国植被对干旱的响应。基于干旱胁迫变化与生长季 NDVI 同期异常之间的非线性关系，我们通过一种结合特征提取、一致性分析和分段线性回归方法来检测干旱阈值的框架，得出了影响中国植被生长的基于卫星的干旱阈值（T ）的空间格局。T 值表示基于百分位数的干旱阈值水平，较小的 T 值对应于更负的土壤湿度异常。平均而言，T 值处于第 8.7 个百分位数，在中国植被覆盖区的 64.4%中可检测到，华北和江汉平原的 T 值较低，内蒙古高原的 T 值较高。此外，森林的 T 值通常低于草地的 T 值。我们还发现，农业灌溉改变了四川盆地农田的干旱阈值。对于未来预测，地球系统模型预测中国将有更多地区面临生态干旱风险增加的情况，河西走廊-河套平原和山东半岛将成为生态干旱的热点地区。本研究对于准确评估干旱对中国植被生长的影响具有重要意义，并为中国陆地生态系统的有效生态管理提供了科学参考。
