Abstract
The responses of forests to nitrogen (N) deposition largely depend on the fates of deposited N within the ecosystem. Nitrogen-fixing legume trees widely occur in terrestrial forests, but the fates of deposited N in legume-dominated forests remain unclear, which limit a global evaluation of N deposition impacts and feedbacks on carbon sequestration. Here, we performed the first ecosystem-scale 15N labeling experiment in a typical legume-dominated forest as well as in a nearby non-legume forest to determine the fates of N deposition between two different forest types and to explore their underlying mechanisms. The 15N was sprayed bimonthly for 1 year to the forest floor in control and N addition (50 kg N ha−1 year−1 for 10 years) plots in both forests. We unexpectedly found a strong capacity of the legume forest to retain deposited N, with 75 ± 5% labeled N recovered in plants and soils, which was higher than that in the non-legume forest (56 ± 4%). The higher 15N recovery in legume forest was mainly driven by uptake by the legume trees, in which 15N recovery was approximately 15% more than that in the nearby non-legume trees. This indicates higher N-demand by the legume than non-legume trees. Mineral soil was the major sink for deposited N, with 39 ± 4% and 34 ± 3% labeled N retained in the legume and non-legume forests, respectively. Moreover, N addition did not significantly change the 15N recovery patterns of both forests. Overall, these findings indicate that legume-dominated forests act as a strong sink for deposited N regardless of high soil N availability under long-term atmospheric N deposition, which suggest a necessity to incorporate legume-dominated forests into N-cycling models of Earth systems to improve the understanding and prediction of terrestrial N budgets and the global N deposition effects.
Originalsprog | Engelsk |
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Tidsskrift | Global Change Biology |
Vol/bind | 28 |
Udgave nummer | 4 |
Sider (fra-til) | 1529–1543 |
Antal sider | 15 |
ISSN | 1354-1013 |
DOI | |
Status | Udgivet - 2022 |
Bibliografisk note
Funding Information:We thank the anonymous reviewers for their valuable comments and suggestions on the manuscript. We appreciate Heshan National Field Research Station of Forest Ecosystems (CAS) for providing the study platform. This study was financially supported by the National Nature Science Foundation of China (41731176, 31700422, 31901164, and 31770523), Youth Innovation Promotion Association CAS (2021346), Guangdong Basic and Applied Basic Research Foundation (2019A1515011821), and Youth Elite Sponsorship Program by ESC (STQT2020A02).
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