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Published on: November 21, 2015
Aridity threshold in controlling ecosystem nitrogen cycling in arid and semi-arid grasslands
Chao Wang1, Xiaobo Wang2, Dongwei Liu3
11] State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China [2] College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China [3].
Abstract:
Higher aridity and more extreme rainfall events in drylands are predicted due to climate change. Yet, it is unclear how changing precipitation regimes may affect nitrogen (N) cycling, especially in areas with extremely high aridity. Here we investigate soil N isotopic values (δ(15)N) along a 3,200 km aridity gradient and reveal a hump-shaped relationship between soil δ(15)N and aridity index (AI) with a threshold at AI=0.32. Variations of foliar δ(15)N, the abundance of nitrification and denitrification genes, and metabolic quotient along the gradient provide further evidence for the existence of this threshold. Data support the hypothesis that the increase of gaseous N loss is higher than the increase of net plant N accumulation with increasing AI below AI=0.32, while the opposite is favoured above this threshold. Our results highlight the importance of N-cycling microbes in extremely dry areas and suggest different controlling factors of N-cycling on either side of the threshold.
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