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Drivers of foliar 15N trends in southern China over the last century
Journal article   Peer reviewed

Drivers of foliar 15N trends in southern China over the last century

Songbo Tang, Jianfeng Liu, Frank S. Gilliam, Peter Hietz, Zhiheng Wang, Xiankai Lu, Feiyan Zeng, Dazhi Wen, Enqing Hou, Yuan Lai, …
Global change biology, Vol.28(18), pp.5441-5452
09/2022
DOI: https://doi.org/10.1111/gcb.16285
PMID: 35653265
Web of Science ID: WOS:000812908800001

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16 Times Cited - Web of Science

Abstract

Foliar stable nitrogen (N) isotopes (delta N-15) generally reflect N availability to plants and have been used to infer about changes thereof. However, previous studies of temporal trends in foliar delta N-15 have ignored the influence of confounding factors, leading to uncertainties on its indication to N availability. In this study, we measured foliar delta N-15 of 1811 herbarium specimens from 12 plant species collected in southern China forests from 1920 to 2010. We explored how changes in atmospheric CO2, N deposition and global warming have affected foliar delta N-15 and N concentrations ([N]) and identified whether N availability decreased in southern China. Across all species, foliar delta N-15 significantly decreased by 0.82 parts per thousand over the study period. However, foliar [N] did not decrease significantly, implying N homeostasis in forest trees in the region. The spatiotemporal patterns of foliar delta N-15 were explained by mean annual temperature (MAT), atmospheric CO2 (PCO2$$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$), atmospheric N deposition, and foliar [N]. The spatiotemporal trends of foliar [N] were explained by MAT, temperature seasonality, PCO2$$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$, and N deposition. N deposition within the rates from 5.3 to 12.6 kg N ha(-1) year(-1) substantially contributed to the temporal decline in foliar delta N-15. The decline in foliar delta N-15 was not accompanied by changes in foliar [N] and therefore does not necessarily reflect a decline in N availability. This is important to understand changes in N availability, which is essential to validate and parameterize biogeochemical cycles of N.

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