相似降水年组下黄土高原植被恢复与土壤水分变化过程与空间特征分析

土壤水分是黄土高原植被恢复及其可持续性的主导限制因子,为认识退耕还林(草)工程以来大尺度植被恢复与土壤水分关系,以25km×25km格点为研究单元,采用1992—2013年逐月降水量、归一化植被指数(NDVI)和土壤水分指数(SWI)等数据,分析了该区植被恢复与土壤水变化过程及其区域分布特征。结果表明,黄土高原植被和土壤水分变化特征和趋势不一致,其中大部分区域(70%以上面积)NDVI呈极显著增加趋势(p0.01),但绝大部分地区(94%面积)的SWI没有趋势性变化。为进一步揭示植被和土壤水分变化关系,以格点为单元提取并分析了相似年组(年降水量差小于2%,年差大于或等于5年,逐月降水量相关性大于0.55),并分析了不同相似年组内NDVI和SWI的变化特征。植被指数与土壤水分变化主要包括两类:植被指数和土壤水分同时增加与植被指数增加而土壤水分减少。黄土高原植被、土壤水分变化的区域性明显,在未来生态恢复过程中,需要进一步认识植被恢复对土壤水分的关系,促进黄土高原植被恢复的可持续性。

Relationships Between Vegetation Restoration and Soil Moisture on the Loess Plateau

On the Loess Plateau,soil moisture is one of the major factors impacting the sustainability of vegetation restoration.In this study,we used datasets on precipitation,vegetation cover and soil moisture content to investigate the changing trends and regional variabilities of vegetation cover and soil moisture across the Loess Plateau between 1992 and 2013 at a 25 km scale.The results showed that:(1) vegetation cover for most areas of the Loess Plateau experienced a significant increasing trend,while soil moisture for majority parts of the plateau underwent an insignificant change;(2) under the similar precipitation condition,there were mainly two types of vegetation cover-soil moisture changes,which were increased vegetation coverage and soil moisture and increased vegetation coverage and decreased soil moisture.Regional variabilities of changes in vegetation cover and soil moisture were large,further studies were desirable to understand the relationship between vegetation restoration and soil moisture changes,and therefore to improve the sustainability of vegetation restoration on the Loess Plateau.