Progressive nitrogen limitation across the Tibetan alpine permafrost region
Dan Kou, Guibiao Yang, Fei Li, Xuehui Feng, Dianye Zhang, Chao Mao, Qiwen Zhang, Yunfeng Peng, Chengjun Ji, Qiuan Zhu, Yunting Fang, Xueyan Liu, Xu-Ri Xu-Ri, Siqi Li, Jia Deng, Xunhua Zheng, Jingyun Fang, Yuanhe Yang
Abstract
The ecosystem carbon (C) balance in permafrost regions, which has a global significance in understanding the terrestrial C-climate feedback, is significantly regulated by nitrogen (N) dynamics. However, our knowledge on temporal changes in vegetation N limitation (i.e., the supply of N relative to plant N demand) in permafrost ecosystems is still limited. Based on the combination of isotopic observations derived from a re-sampling campaign along a ~3000 km transect and simulations obtained from a process-based biogeochemical model, here we detect changes in ecosystem N cycle across the Tibetan alpine permafrost region over the past decade. We find that vegetation N limitation becomes stronger despite the increased available N production. The enhanced N limitation on vegetation growth is driven by the joint effects of elevated plant N demand and gaseous N loss. These findings suggest that N would constrain the future trajectory of ecosystem C cycle in this alpine permafrost region.