PJB-2021-485
EFFECTS OF N ENRICHMENT ON N STOCKS AND THEIR RESPONSES TO WATER ADDITION IN INNER MONGOLIA TEMPERATE STEPPE
Iqnaa Naseer
Abstract
Grassland’s key processes of N-cycle affected dramatically by nitrogen (N) enrichment under current global climate change. N availability is very critical for its storage and cycling; however, water conditions modulate these impacts remain unclear, especially when an altered precipitation regime is taken into consideration. Based on a five-year manipulative field experiment, with N (10 g N m-2 yr-1) and water additions (80 mm yr-1, in terms of five intensities, i.e., 2 mm×40 times, 5 mm×16 times, 10 mm×8 times, 20 mm×4 times, and 40 mm×2 times) in a typical temperate steppe in Inner Mongolia, we analyzed the effects of nitrogen addi-tion on N content and N stocks in the aboveground plant tissues, soil, and aboveground litter, and the role that water condition played thereof. We found that N enrichment significantly enhanced N content and N stock of aboveground plant tissues. N content and N stock of aboveground litter, also increased by N enrichment, but it is only significant after two years of N addition. Soil N content in N-addition treatments decreased in the first year of the experiment but increased after that. Higher water availability decreased the N addition-induced increase of N content of aboveground plant tissues and litter and litter N stock, but not plant N stock. There are no apparent effects of water addition on the N addition-induced impacts on soil N content. It is noteworthy that the impacts of water conditions on N addition-induced changes of the three N stocks were not affected by the intensity of water added. Our work has important implications for obtaining an advanced understanding of grassland response to N deposition and altered precipitation regime.
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