A threshold reveals decoupled relationship of sulf

Authors: Wentao Luo Feike A Dijkstra Edith Bai Jiao Feng XiaoTao Lü Chao Wang Honghui Wu MaiHe Li Xingguo Han Yong Jiang

Publish Date: 2015/12/26

Volume: 127, Issue: 1, Pages: 141-153

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Abstract

How climatic factors influence the balance of sulfur S with carbon C and nitrogen N in soils is not well understood Here we report the results of S C and N concentrations in 550 soil samples along a 3500km aridity gradient across arid and semiarid grasslands in northern China Our results showed that soil available S AS concentrations decreased with increasing aridity index AI calculated as ‘1—the ratio of mean annual precipitation to potential evapotranspiration’ when AI  091 90–450 mm rainfall year−1 but increased when AI  091 30–90 mm rainfall year−1 having a threshold at AI = 091 90 mm rainfall year−1 Soil AS concentrations were positively related to soil organic C OC soil total N TN microbial biomass C and N concentrations and arylsulphatase activities when AI  091 but were not positively related to these variables when AI  091 Topsoil ASOC and ASTN ratios mainly depended on OC and TN concentrations when AI  091 but mainly depended on AS concentrations when AI  091 The decreased AI  091 and increased total S concentrations AI  091 with increasing AI along the gradient provided further evidence for the existence of this fundamental threshold High concentrations of sulfate in drier soils were associated with longterm atmosphere inputs and groundwaterderived salts with minimal leaching rates Overall our findings imply that aridity asymmetrically controls the relationships of soil AS with OC and TN on the two sides of the threshold ie biological processes exerted stronger controls in wetter sites while geochemical processes played more significant roles in drier sites These results should be incorporated into predictive models of global biogeochemical cycling under various global climate change scenariosWilliam H Schlesinger is gratefully acknowledged for his comments and suggestions We thank all members of the Field Expedition Team from the Institute of Applied Ecology Chinese Academy of Sciences for assistance with field data collection This work was financially supported by the National Natural Science Foundation of China 41371251 National Basic Research Program of China 2011CB403204 and State Key Laboratory of Forest and Soil Ecology LFSE201301

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