Nitrogen dynamics of alpine swamp meadows are less responsive to climate warming than that of alpine meadows

• Published in: Science of The Total Environment
• Main Authors: Chen, Xiaopeng, Wang, Genxu, Li, Na, Chang, Ruiying, Zhang, Tao, Mao, Tianxu, Song, Chunlin, Huang, Kewei
• Format: Report
• Language: English
• Published: ELSEVIER 2024
• Subjects: Freeze-thaw cycles; Permafrost; Upland; Wetland; 15N tracing; GHG FLUX; FERTILIZATION; DEPOSITION; CARBON; Environmental Sciences & Ecology; Environmental Sciences; permafrost
• Online Access: http://ir.imde.ac.cn/handle/131551/58198; https://doi.org/10.1016/j.scitotenv.2024.172446

The freeze-thaw cycle mediates permafrost soil hydrothermal status, nitrogen (N) mineralization, and loss. Furthermore, it affects root development and competition among nitrophilic and other species, shaping the pattern of N distribution in alpine ecosystems. However, the specific N dynamics during the growing season and N loss during the non-growing season in response to climate warming under low- and high-moisture conditions are not well documented. Therefore, we added 15N tracers to trace the fate of N in warmed and ambient alpine meadows and alpine swamp meadows in the permafrost region of the Qinghai-Tibet Plateau. During the growing season, warming increased 15N recovery (15Nrec) in shoots of K. humilis, litters, 0-5 and 5-20 cm roots in the alpine meadow by 149.94 % f 52.87 %, 114.58 % f 24.43 %, 61.11 % f 32.27 %, and 97.12 % f 42.92 %, respectively, while increased 15Nrec of litters by 151.55 % f 27.06 % in the alpine swamp meadow. During the non-growing season, warming reduced 15N stored in roots by 486.77 % f 57.90 %, though increased the 15N recovery in 5-20 cm soil depth by 76.68 % f 39.42 % in the alpine meadow, whereas it did not affect N loss during the non-growing season in the alpine swamp meadow. Overall, warming promoted N utilization by increasing the plant N pool during the growing season, and enhanced root N loss and downward migration during the non-growing season due to the freeze-thaw process, which may result in fine root turnover and cell destruction releasing N in the alpine meadow. Conversely, the N dynamics of alpine swamp meadows were less responsive to climate warming.