黄土高原植被变化对气象干旱多尺度响应特征与机制

基于黄土高原1983—2015年间的植被状况指数(VCI)与1~48个月尺度的标准化降水蒸散发指数(SPEI)和标准化降水指数(SPI),利用Pearson相关系数法、线性回归法和Mann-Kendall趋势检验法等方法研究了黄土高原地区植被对气象干旱的多时间尺度时空响应特征。结果表明:(1)1983—2015年,黄土高原植被状况整体趋于改善,但黄土高原整体干湿状况变化趋势不大。(2)黄土高原绝大部分区域植被变化与气象干旱指数呈现显著正相关关系,表明植被活动受到水分的限制较强。但是,过去几十年,黄土高原地区植被受到水分限制的影响程度有逐渐减轻的趋势。(3)黄土高原植被对短时间尺度的水分盈亏变化相对敏感,尤其是耕地和草地对1~4个月的SPEI更为敏感,而林地对SPEI的响应时间尺度较为分散。黄土高原VCI与SPEI、SPI的最大相关系数均主要出现在生长季(4—10月),表明水分条件在生长季对植被活动的影响较为显著。

Multi-scale Response Characteristics and Mechanism of Vegetation to Meteorological Drought on the Loess Plateau

In this study, based on Vegetation Condition Index (VCI) of the Loess Plateau from 1983 to 2015, Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Precipitation Index (SPI) at the scale of 1~48 months, we investigated the spatial-temporal response characteristics of vegetation to meteorological drought index at multi time-scales on the Loess Plateau through Pearson correlation coefficient method, linear regression method and Mann Kendall trend test method. The results showed that: (1) The overall vegetation condition of the Loess Plateau improved, but no significant drying or wetting trend could be detected in the study area during 1983 and 2015. (2) The change of vegetation was well positively correlated to the meteorological drought index in most areas of the Loess Plateau, indicating that the vegetation growth was largely restricted by the moisture in the study area. However, in the past few decades, such restriction effect from atmospheric moisture to the vegetation was gradually weakening. (3) The vegetation on the Loess Plateau was relatively much more sensitive to the change of water balance at a short time sale, the cultivated land and grassland were more sensitive to the SPEI of 1~4 months, while the response time-scale of forest land to SPEI was relatively scattered. Furthermore, the maximum correlation coefficient between VCI and SPEI or SPI on the Loess Plateau mainly occurred during the growing season (April to October), indicating that the water conditions had a much more significant effect on vegetation growth during growing season.