δ15N of soil N and plants in a N‐saturated,subtropical forest of southern China |
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Authors: | K Koba K Isobe Y Takebayashi YT Fang Y Sasaki W Saito M Yoh J Mo L Liu X Lu T Zhang W Zhang K Senoo |
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Institution: | 1. Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu 1838509, Japan;2. Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113‐8657, Japan;3. South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou 510650, China |
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Abstract: | We investigated the δ15N profile of N (extractable NH , NO , and organic N (EON)) in the soil of a N‐saturated subtropical forest. The order of δ15N in the soil was EON > NH > NO . Although the δ15N of EON had been expected to be similar to that of bulk soil N, it was higher than that of bulk soil N by 5‰. The difference in δ15N between bulk soil N and EON (Δ15Nbulk‐EON) was correlated significantly with the soil C/N ratio. This correlation implies that carbon availability, which determines the balance between N assimilation and dissimilation of soil microbes, is responsible for the high δ15N of EON, as in the case of soil microbial biomass δ15N. A thorough δ15N survey of available N (NH , NO , and EON) in the soil profiles from the organic layer to 100 cm depth revealed that the δ15N of the available N forms did not fully overlap with the δ15N of plants. This mismatch in δ15N between that of available N and that of plants reflects apparent isotopic fractionation during N uptake by plants, emphasizing the high N availability in this N‐saturated forest. Copyright © 2010 John Wiley & Sons, Ltd. |
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