Warming, permafrost thaw and increased nitrogen availability as drivers for plant composition and growth across the Tibetan Plateau

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Permafrost-affected ecosystems are subject to warming and thawing, which can increase the availability of subsurface nitrogen (N) with consequences in otherwise N-limited tundra and alpine vegetation. Here, we quantify the extent of warming and permafrost thawing and the corresponding effects on nitrogen availability and plant growth based on a 20-year survey across 14 sites on the Tibetan Plateau. The survey showed that most sites have been subject to warming and thawing and that the upper permafrost zone across all sites was rich in inorganic N, mainly as ammonium. We further explore the efficiency of plants to utilize 15N-labelled inorganic N over five years following 15N addition at the permafrost table far below the main root zone. The 15N experiment showed that deep-rooted plant species were able to utilize the labelled N. A SEM model suggests that changes in vegetation can be explained by both active layer warming and permafrost thawing and the associated changes in inorganic nitrogen availability. Our results highlight a feedback mechanism of climate warming, in which released plant-available N may favour deep-rooted plants. This can explain important changes in plant composition and growth across the sites on the Tibetan Plateau.
TidsskriftSoil Biology and Biochemistry
Antal sider9
StatusUdgivet - 2023

Bibliografisk note

Funding Information:
BE and HY were supported by the Danish National Research Foundation (CENPERM DNRF 100). In addition, QB was supported by the National Natural Science Foundation of China ( 42230512 ), JT by the Swedish Formas grant (no. 2016-01580 ), Qing Zhu by the U.S. Department of Energy Reducing Uncertainties in Biogeochemical Interactions through Synthesis and Computation (RUBISCO), W. Z. by the Swedish Research Council VR ( 2020–05338 ) and Swedish National Space Agency ( 209/19 ), HB was supported by the Chinese Academy of Sciences ( YJKYYQ20190012 and E229060201 ) and State Key Laboratory of Frozen Soil Engineering ( SKLFSE-ZT-202111 ). We thank Anping Chen and Yiqi Luo for their suggestions about the experiment design. We thank Yongzhi Liu, Huijun Jin, Chao Mao, Guojun Liu, and Guilong Wu for field soil sample processing and laboratory analyses. We also thank Licheng Liu and Youmi Oh for aiding with the structure equation model. In addition, our gratitude goes to Sebastian Zastruzny, Laura Helene Rasmussen, Emily P. Pedersen, Anne Christine Krull Pedersen, and Lena Hermesdorf for providing comments on the data analysis. Finally, we would like to acknowledge the very helpful comments from two journal reviewers.

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