Annual ecosystem respiration is resistant to changes in freeze–thaw periods in semi-arid permafrost

• Published in: Global Change Biology
• Main Authors: Wang, Qi, Lv, Wangwang, Li, Bowen, Zhou, Yang, Jiang, Lili, Piao, Shilonog, Wang, Yanfen, Zhang, Lirong, Meng, Fandong, Liu, Peipei, Hong, Huan, Li, Yaoming, Dorji, Tsechoe, Luo, Caiyun, Zhang, Zhenhua, Ciais, Philippe, Peñuelas, Josep, Kardol, Paul, Zhou, Huakun, Wang, Shiping
• Other Authors: Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), National Natural Science Foundation of China, NSFC: 41731175, 41988101 Chinese Academy of Sciences, CAS: XDA20050101, XDA2005010405 National Key Research and Development Program of China, NKRDPC: 2016YFC0501802, 31672470, This work was supported by projects from the National Natural Science Foundation of China (41731175 and 41988101), Strategic Priority Research Program A of the Chinese Academy of Sciences (XDA20050101 and XDA2005010405), National Key Research and Development Program of China (2016YFC0501802) and National Natural Science Foundation of China (31672470).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: ecosystem respiration; freeze–thaw events; number and frequency of freeze–thaw cycles; precipitation addition; semi-arid with ice-poor permafrost; Tibetan Plateau; warming gradient; [SDE.MCG]Environmental Sciences/Global Changes; Ice; permafrost
• Online Access: https://hal.science/hal-03227860; https://doi.org/10.1111/gcb.14979

International audience Warming in cold regions alters freezing and thawing (F–T) of soil in winter, exposing soil organic carbon to decomposition. Carbon-rich permafrost is expected to release more CO2 to the atmosphere through ecosystem respiration (Re) under future climate scenarios. However, the mechanisms of the responses of freeze–thaw periods to climate change and their coupling with Re in situ are poorly understood. Here, using 2 years of continuous data, we test how changes in F–T events relate to annual Re under four warming levels and precipitation addition in a semi-arid grassland with discontinuous alpine permafrost. Warming shortened the entire F–T period because the frozen period shortened more than the extended freezing period. It decreased total Re during the F–T period mainly due to decrease in mean Re rate. However, warming did not alter annual Re because of reduced soil water content and the small contribution of total Re during the F–T period to annual Re. Although there were no effects of precipitation addition alone or interactions with warming on F–T events, precipitation addition increased total Re during the F–T period and the whole year. This decoupling between changes in soil freeze–thaw events and annual Re could result from their different driving factors. Our results suggest that annual Re could be mainly determined by soil water content rather than by change in freeze–thaw periods induced by warming in semi-arid alpine permafrost.