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

Xiaopeng Chen; Genxu Wang; Na Li; Ruiying Chang; Tao Zhang; Tianxu Mao; Chunlin Song; Kewei Huang

doi:10.1016/j.scitotenv.2024.172446

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

Sci Total Environ. 2024 Jun 10:928:172446. doi: 10.1016/j.scitotenv.2024.172446. Epub 2024 Apr 14.

Authors

Xiaopeng Chen¹, Genxu Wang², Na Li³, Ruiying Chang⁴, Tao Zhang⁵, Tianxu Mao⁶, Chunlin Song⁷, Kewei Huang⁸

Affiliations

¹ College of Grassland Science, Shanxi Agricultural University, Taigu 030801, China.
² State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China. Electronic address: wanggx@scu.edu.cn.
³ Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.
⁴ Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China.
⁵ Institute of New Rural Development, Guizhou University, Guiyang 550025, China.
⁶ College of Forestry, Guizhou University, Guiyang 550025, China.
⁷ State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China.
⁸ Hubei Key Laboratory of Basin Water Security, Changjiang Survey, Planning, Design and Research Co., Ltd., Wuhan 430010, China.

PMID: 38621528
DOI: 10.1016/j.scitotenv.2024.172446

Abstract

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 (¹⁵N_rec) in shoots of K. humilis, litters, 0-5 and 5-20 cm roots in the alpine meadow by 149.94 % ± 52.87 %, 114.58 % ± 24.43 %, 61.11 % ± 32.27 %, and 97.12 % ± 42.92 %, respectively, while increased ¹⁵N_rec of litters by 151.55 % ± 27.06 % in the alpine swamp meadow. During the non-growing season, warming reduced ¹⁵N stored in roots by 486.77 % ± 57.90 %, though increased the ¹⁵N recovery in 5-20 cm soil depth by 76.68 % ± 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.

Keywords: (15)N tracing; Freeze-thaw cycles; Permafrost; Upland; Wetland.