MODIS detection of vegetation changes and investigation of causal factors in Poyang Lake basin, China for 2001-2015

In recent decades, vegetation has shown an overall greening trend in response to rising global temperatures. At the same time, vegetation browning is still worthy of attention, particularly in humid regions with dense vegetation coverage. This study used 15 years (2001-2015) of Terra Moderate-resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data in an effort to detect the overall trends and abrupt changes in vegetation activity over the Poyang Lake basin, which is a typical humid region that contains the largest freshwater lake in China. MODIS NDVI data showed a vegetation greening trend over 94.9% of the basin land. Although the basin has been extensively afforested since the 1980s, there was still a vegetation browning trend over 5.1% of the basin land area, primarily as a result of urbanization. Abrupt vegetation decreases were observed over 7.9% of the basin land area from 2004 to 2012. Most of the decreases were likely caused by the nationwide snow storms in early 2008 and the widespread insect outbreaks as a result of abnormal hydrometeorological conditions. Abrupt vegetation increases were observed over 1.6% of the basin land area in the same period. Most of the increases were likely attributed to the continued efforts of afforestation that transformed large woody savanna lands to mixed forests. The results provided spatial details, time nodes and causal factors of vegetation changes, particularly vegetation decreases, which will benefit government organizations when taking remedial measures.