Impacts of Nitrogen Deposition on China’s Grassland Ecosystems

Abstract

Grasslands account for 40% of national land area in China, with great influences on economic development and ecological security. Atmospheric nitrogen (N) deposition has increased dramatically in China during last three decades and is expected to remain relatively high in the next few decades. By comparing the status of grasslands in the 1980s and 2000s, it has been found that N deposition increased the N:P ratio and reduced soil pH and cation exchange capacity in the grasslands of China. Here, we review scientific advances in the impacts of N deposition on Chinese grasslands in recent decades by focusing the changes of above- and belowground biodiversity and carbon and nutrient cycling. We also introduced the experimental setups with respect to N deposition in diverse types of grasslands in China. Nitrogen deposition leads to soil eutrophication with the substantial increases of soil N availability and thus changes soil nutrient cycling through soil- and plant-mediated pathways. Nitrogen addition alters fluxes of greenhouse gas (GHG) and interactively with precipitation and temperature factors affected GHG emissions. Mounting evidence showed that N deposition threatens biodiversity in the grasslands of China, in that N deposition would reduce species richness in above- and belowground communities through acidifying soil and triggering metal toxicity.