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

• Published in: Soil Biology and Biochemistry
• Main Authors: Yun, Hanbo, Zhu, Qing, Tang, Jing, Zhang, Wenxin, Chen, Deliang, Ciais, Philippe, Wu, Qingbai, Elberling, Bo
• Other Authors: Lanzhou University, Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management Copenhagen (IGN), Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH)-Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), Purdue University West Lafayette, Lawrence Berkeley National Laboratory Berkeley (LBNL), Department of Physical Geography and Ecosystem Science Lund, Skane University Hospital Lund, University of Copenhagen = Københavns Universitet (UCPH), Department of Earth Sciences Gothenburg, Göteborgs Universitet = University of Gothenburg (GU), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: Nitrogen Permafrost thawing Climate warming Tibetan plateau; [SDU]Sciences of the Universe [physics]; permafrost; Tundra
• Online Access: https://hal.science/hal-04092611; https://hal.science/hal-04092611/document; https://hal.science/hal-04092611/file/1-s2.0-S0038071723001037-main.pdf; https://doi.org/10.1016/j.soilbio.2023.109041

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 15 N-labelled inorganic N over five years following 15 N addition at the permafrost table far below the main root zone. The 15 N 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.