Attribution of the vegetation trends in a typical desertified watershed of northeast China over the past three decades

Abstract

AbstractDesertification is a serious environmental problem in north China that should be urgently addressed and prevented. Identifying the causes of vegetation trends that are closely related to desertification is prerequisite for a better control of desertification processes. In this study, the Xiliao River basin, a typical desertified watershed in northeast China, was selected as a case study. To partition the vegetation trends into climate‐induced and human‐induced trends, a linear regression model, piecewise regression model and a binary nonlinear regression analysis were employed, based on the long‐term remote measures of the Normalized Difference Vegetation Index (NDVI) and climate data. The results showed that the spatial pattern of the vegetation trends in the basin was highly heterogonous, although the climatic factors varied similarly. In the north, where natural vegetation dominates, the vegetation exhibited significant browning (−0.0015 year−1), and a significant changing point was observed in 2000. In the south, where cropland dominates, the vegetation exhibited significant greening (0.002 year−1). Approximately 82.7% of the area with a decreasing NDVI was attributed to climate variability. The main reason for the vegetation degradation was because of a multiyear reduction in precipitation from 1999 to 2011 rather than from an increase in the grazing size. Approximately 67.0% of the area with an increasing NDVI could be attributed to irrigation, which overexploited a large amount of water resources, even though significantly increasing air temperatures can promote vegetation greenness. Our findings have important management implications for grazing and agriculture in the context of controlling desertification and sustaining environment. Copyright © 2016 John Wiley & Sons, Ltd.