Authors: ShuLan Cheng HuaJun Fang GuiRui Yu TianHong Zhu JiaoJiao Zheng
Publish Date: 2010/08/13
Volume: 337, Issue: 1-2, Pages: 285-297
Abstract
The natural abundance of 15N δ15N in plants and soils is an ideal tool for assessing ecosystem N dynamics However many of the mechanisms driving the variability of foliar and soil δ15N values within and across ecosystems are still unclear In this study we analyzed the patterns of N concentrations and δ15N values in leaves bulk soils and soil mineral N as well as soil N turnover rates across four temperate and boreal forest ecosystems along a mountain transect The results showed that plant species and soil properties directly controlled soil δ15N patterns and climate factors air temperature and precipitation indirectly affected foliar δ15N patterns Foliar N concentrations varied consistently with the concentrations of soil available N and soil NO 3 − N whereas foliar δ15N was most closely associated with the δ15N of soil NH 4 + the most abundant form of N in soil solution 15N enrichment in surface mineral soil in high elevation forests was mainly attributed to 15Nenriched organic N accumulation Furthermore the foliar enrichment factor εp/s = δ15Nfoliage−δ15Nsoil was significantly correlated with N transformation and loss rates and was negatively correlated with the ratio of NH 4 + to total inorganic N These results suggest that foliar δ15N value and foliar N concentration together accurately reflect the N availability of forest ecosystems Foliar εp/s can act as an integrated proxy to reflect the status of N cycling within or across forest ecosystems Soil nitrification and species’ NH 4 + to NO 3 − uptake ratios are key processes controlling foliar δ15N patterns in Nlimited forest ecosystems Our findings improve the mechanistic understanding of the commonly observed variability in foliar and soil δ15N within and across forest ecosystemsThis research was funded by the National Key Research and Development Program 2010CB833501 2010CB833502 the National Natural Science Foundation of China 30600071 40601097 30590381 the Knowledge Innovation Project of the Chinese Academy of Sciences KZCX2YW432 O7V70080SZ LENOM07LS01 and the President Fund of GUCAS O85101PM03 We gratefully acknowledge Dr Rebecca Sherry Dr Yuanhe Yang and Dr Xuhui Zhou for revising the English writing of the manuscript We appreciate the two anonymous reviewers and the editor for their valuable suggestions and effort on this paper
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