1] 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].
1] 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] Department of Microbiology and Plant Biology, Institute for Environmental Genomics, University of Oklahoma, Norman, Oklahoma 73019, USA [4].
Nat Commun. 2014 Sep 4;5:4799. doi: 10.1038/ncomms5799.
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.
由于气候变化，预计干旱地区的干旱程度和极端降雨事件将增加。然而，目前尚不清楚降水模式的变化将如何影响氮（N）循环，特别是在干旱程度极高的地区。在这里，我们沿着 3200 公里的干旱梯度调查了土壤 N 同位素值（δ(15)N），并揭示了土壤 δ(15)N 与干旱指数（AI）之间呈驼峰形关系，其阈值为 AI=0.32。叶片 δ(15)N、硝化和反硝化基因丰度以及沿梯度的代谢商的变化为这种阈值的存在提供了进一步的证据。数据支持这样的假设，即在 AI<0.32 时，随着 AI 的增加，气态 N 损失的增加高于净植物 N 积累的增加，而在这个阈值以上，则有利于相反的情况。我们的结果强调了在极干旱地区氮循环微生物的重要性，并表明在阈值两侧，氮循环的控制因素不同。
