植被对不同时间尺度干旱事件的响应特征及成因分析

利用标准化降雨蒸散发指数(SPEI)与归一化植被指数(NDVI)系统研究了中国不同区域、不同土地利用类型的植被对不同时间尺度干旱事件的响应特征,并对成因做出探讨。研究表明:(1)全国大部分区域NDVI与SPEI呈显著正相关,表明中国大部分区域植被生物量变化受干旱时空特征的影响。而沿北纬30度附近的长江流域区域,尤其是长江流域东南部、珠江流域下游等降水相对丰沛区域;黑龙江东北部及长白山地区、四川西部等高寒区域,NDVI与SPEI表现出弱相关性,受干旱影响较小;(2)多年平均水平衡是影响植被对干旱响应的关键因素,土壤水分变化是植被活力与生物量变化的关键影响因子。多年平均日照时数较长的区域,植被变化受干旱影响较大。从对干旱影响敏感性程度来讲,越是水量丰沛的区域,植被受干旱的影响越小,其中,草地对干旱的影响最为敏感,其次为灌木与森林。

Vegetation responses to drought at different time scales in China

NDVI and SPEI drought index are collected and analyzed to investigate vegetation responses to drought regimes at different time scales in different regions and vegetation types across China, and the causes of changes are discussed. The results show that: 1) SPEI and NDVI are significantly positively correlated in most regions of China, indicating that the changes in vegetation biomass are influenced mainly by spatiotemporal characteristics of available water. The southeastern Yangtze River basin and the lower Pearl River basin are characterized by abundant precipitation and vegetation that is not sensitive to drought. The northeastern Heilongjiang Province, the Changbai Mountains, and the western Sichuan Province are characterized by weak correlation between NDVI and SPEI, indicating small effect of drought on vegetation. (2) The effects of the average water balance, average annual rainfall, average annual effective accumulated temperature, and average daily sunshine hours on correlations between NDVI and SPEI show that the average water balance is the key factor behind the changes in vegetation vigor. Hence, it can be concluded that change in soil moisture is the key factor determining the changes in vegetation activity and biomass. Regional precipitation or water balance is related significantly to the correlation between SPEI and NDVI, whereas vegetation in the regions with longer sunshine hours is more sensitive to droughts. In general, grasslands are the most sensitive to droughts, followed shrubs and forest.