Annual ecosystem respiration is resistant to changes in freeze–thaw periods in semi‐arid permafrost. (17th February 2020)

• Record Type: Journal Article
• Authors: Wang, Qi; Lv, Wangwang; Li, Bowen; Zhou, Yang; Jiang, Lili; Piao, Shilong; 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
• Is Part Of: Global change biology. Volume 26:Number 4(2020)
• Page Start: 2630
• Page End: 2641
• Publication Date: 2020-02-17
• 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; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.14979
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: 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. Abstract : Factors affecting ecosystem respiration (Re) of entire year. Soil water content (SWC) has directly positive effect on Re of entire year. Soil temperature (ST) has indirectly positive effect on Re of the entire year through effect on duration of frozen period. ANPP, aboveground net primary productivity; DF, duration of frozen period; NFT, number of freeze‐thaw cycles; OLO, onset of leaf‐out; Re, total annual accumulated ecosystem CO2 respiration; RMSEA, root mean square error of approximation; ST5‐max, maximum soil temperature at 5 cm during the freeze‐thaw period; ST5‐min, minimum soil temperature at 5 cm during the freeze‐thaw period.