Warming effects on methane fluxes differ between two alpine grasslands with contrasting soil water status

• Published in: Agricultural and Forest Meteorology
• Main Authors: Li, Fei, Yang, Guibiao, Peng, Yunfeng, Wang, Guanqin, Qin, Shuqi, Song, Yutong, Fang, Kai, Wang, Jun, Yu, Jianchun, Liu, Li, Zhang, Dianye, Chen, Kelong, Zhou, Guoying, Yang, Yuanhe
• Format: Article in Journal/Newspaper
• Language: English
• Published: ELSEVIER 2020
• Subjects: Alpine ecosystems; Carbon cycle; Carbon-climate feedback; Climate warming; Methane emission; Methane uptake; Agronomy; Forestry; Meteorology & Atmospheric Sciences; GREENHOUSE-GAS EMISSIONS; PERMAFROST THAW; NITROGEN-FERTILIZATION; CARBON-DIOXIDE; CLIMATE-CHANGE; TIBETAN PLATEAU; GHG FLUX; TEMPERATURE; PEAT; CH4; Agriculture; Peat; permafrost
• Online Access: http://ir.ibcas.ac.cn/handle/2S10CLM1/18115; https://doi.org/10.1016/j.agrformet.2020.107988

Soil moisture plays a vital role in regulating the direction and magnitude of methane (CH4) fluxes. However, it remains unclear whether the responses of CH4 fluxes to climate warming exhibit difference between dry and moist ecosystems. Based on standardized manipulative experiments (i.e., consistent experimental design and measurement protocols), here we explored warming effects on growing season CH4 fluxes in two alpine grasslands with contrasting water status on the Tibetan Plateau. We observed that experimental warming enhanced CH4 uptake in the relatively arid alpine steppe, but had no significant effects on CH4 emission in the moist swamp meadow. The distinct responses of CH4 fluxes were associated with the different warming effects on biotic and abiotic factors related to CH4 oxidation and production processes. Warming decreased soil water-filled pore space (WFPS) and increased the pmoA gene abundance and CH4 oxidation potential in the alpine steppe, which together led to a significant increase in CH4 uptake at this alpine steppe site. However, warming-induced enhancement in CH4 oxidation potential might be counteracted by the simultaneously increased CH4 production potential in the swamp meadow, which could then result in insignificant warming effects on CH4 emission at this swamp meadow site. Based on a meta-analysis of warming effects on CH4 fluxes across the entire Tibetan Plateau, we found that the entire alpine grasslands could absorb an extra 0.042 Tg CH4 (1 Tg = 10(12) g) per growing season if soil temperature increased by 1 degrees C. These findings demonstrate that warming effects on CH4 fluxes differ between two alpine grasslands with contrasting moisture conditions and the entire alpine grasslands may not trigger a positive CH4 feedback to climate system with moderate warming.