Abstract
BackgroundBoth climate warming and atmospheric nitrogen (N) deposition are predicted to affect soil N cycling in terrestrial biomes over the next century. However, the interactive effects of warming and N deposition on soil N mineralization in temperate grasslands are poorly understood.Methodology/Principal FindingsA field manipulation experiment was conducted to examine the effects of warming and N addition on soil N cycling in a temperate grassland of northeastern China from 2007 to 2009. Soil samples were incubated at a constant temperature and moisture, from samples collected in the field. The results showed that both warming and N addition significantly stimulated soil net N mineralization rate and net nitrification rate. Combined warming and N addition caused an interactive effect on N mineralization, which could be explained by the relative shift of soil microbial community structure because of fungal biomass increase and strong plant uptake of added N due to warming. Irrespective of strong intra- and inter-annual variations in soil N mineralization, the responses of N mineralization to warming and N addition did not change during the three growing seasons, suggesting independence of warming and N responses of N mineralization from precipitation variations in the temperate grassland.Conclusions/SignificanceInteractions between climate warming and N deposition on soil N cycling were significant. These findings will improve our understanding on the response of soil N cycling to the simultaneous climate change drivers in temperate grassland ecosystem.
Highlights
Anthropogenic increases in global atmospheric CO2 concentration are contributing to rising global temperatures over some areas, including northeastern China [1,2]
There was a significant interaction between warming and N addition in affecting soil temperature (F1, 20 = 4.97, P,0.05), in that warming significantly increased soil temperature under ambient N level but not under N-enriched conditions
In 2009, 67% of the changes in soil nitrification rate (NNR) can be explained by the combination of soil B: F, total PLFAs and soil C: N. These results suggest that abiotic and biotic factors played important roles in regulating spatial variations in soil N mineralization in the temperate grassland
Summary
Anthropogenic increases in global atmospheric CO2 concentration are contributing to rising global temperatures over some areas, including northeastern China [1,2]. As a main limiting factor for plant growth and net primary productivity [8,9], understanding soil N availability and its response to climatic and atmospheric changes are vital for soil N dynamics and net primary production and global C budgets in terrestrial ecosystems [10,11]. Both climate warming and atmospheric nitrogen (N) deposition are predicted to affect soil N cycling in terrestrial biomes over the century. The interactive effects of warming and N deposition on soil N mineralization in temperate grasslands are poorly understood
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