The Distribution and Drivers of Land Degradation in the Three-North Shelter Forest Region of China during 1982-2006

It is important to conduct studies on spatio-temporal distribution and drivers based on remote sensing for quantitative estimation of large-scale regional land degradation. In this paper, we analyze the land degradation trend in the Three-North Shelter Forest region of China from 1982 to 2006, using the remotely-sensed data of NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) based on the Sen+ Mann-Kendall trend analysis method, and assess the combined effect of human activities and precipitation on the regional land degradation by using the Residual Trends model. The results indicate that the land degradation have a declining trend as a whole, with the significant increase and the significant decrease being 13.00% and 17.29%, respectively. Land degradation in most of the provinces tends to be relatively slight, especially in Inner Mongolia, Qinghai and Xinjiang, while Gansu witnesses the opposite trend. Human activities contributed 11.93% to the significant vegetation increase, and 6.19% to the degradation. This means that in the arid or semi-arid regions, the temporal change of prccipitation is not significant, so the obvious vegetation change is mainly affected by human activities.