Land degradation monitoring using terrestrial ecosystem carbon sinks/sources and their response to climate change in China

Global warming, which is mainly caused by greenhouse gases, can greatly aggravate land degradation; therefore, the examination of the NEP (net ecosystem productivity) and the analysis of its response to climate change are very critical for understanding carbon cycling. Based on Moderate Resolution Imaging Spectroradiometer data, meteorological data, and soil organic carbon data, this study examined the NEP from 2000 to 2013 and investigated how ongoing climate change affects the NEP. The study results indicate that the terrestrial ecosystems in China generally act as net carbon sinks with increasing NEP values. The western inland region and part of northeast China mainly act as carbon sources, with the NEP exhibiting an increasing trend, whereas the other regions mainly act as carbon sinks, with the NEP showing a decreasing trend across large areas of southern China, where the most obvious land degradation occurs. Homogeneity and heterogeneity co-occur. The general pattern is that ecosystems with high biomass usually have a high NEP value, acting as high carbon sinks in relatively wet and warm environments, but have a low value and even act as carbon sources in dry and cold environments. Both moderate precipitation and temperature are essential in increasing the NEP, whereas lower precipitation and temperatures might have negative effects. Heterogeneity also widely breaks up the general pattern. Temporally, more NEP grids were positively correlated with changes in temperature and showed stronger correlation coefficients with temperature than with precipitation, but the grids showing a significant correlation with these factors accounted for only a small proportion of the total for both precipitation and temperature.