Carbon Sink of a Very High Marshland on the Tibetan Plateau. Issue 4 (6th April 2021)

• Record Type: Journal Article
• Authors: Qi, Yahui; Wei, Da; Zhao, Hui; Wang, Xiaodan
• Is Part Of: Journal of geophysical research. Volume 126:Issue 4(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-04-06
• Subjects: carbon -- eddy covariance -- marshland -- permafrost -- Tibetan Plateau -- warming; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2020JG006235
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: The Tibetan Plateau (TP) is home to the most extensive alpine permafrost, where there are over 30% of China's marshlands. Though climate warming of 0.26°C per decade may have altered the carbon (C) balance by promoting permafrost C release. To date, most studies have been conducted in the eastern TP region (<3, 500 m in altitude), even though 51% of the TP's marshlands are located at altitudes above 4, 500 m, where climate warming is even faster than at lower altitudes. Thus, we set up an eddy covariance system at a very high marshland (4, 760 m in altitude) in the hinterland of the TP and recorded observations for three consecutive years. The results showed that the marshland functioned as a net C sink (187 ± 29 g C m −2 yr −1, Mean ± SD), which is even stronger than at lower altitude marshlands, possibly because of cold‐constraints on respiration. Temperature and vapor pressure deficit together dominated the variation in C exchanges. Moreover, the ecosystem functioned as a net C sink when the average daily temperature exceeded 8°C. Photosynthesis was consistently more sensitive to temperature variation, compared with C release, at the annual, seasonal, and daily scales, which was then validated across other marshlands on the TP. All these pieces of evidence suggest that high‐altitude marshlands on the TP are still functioning as C sinks, and photosynthesis is more sensitive to temperature than C release implies that a warmer climate will benefit the C accumulation, before there is too much soil C loss. Key Points: Cold‐constrained respiration accounted for 68% of gross primary productivity, resulting in a carbon (C) sink of 187 g C m −2 yr −1 The ecosystem functioned as a net C sink when the average daily temperature exceeded 8°C Site‐scale and regional scale revealed that C uptake is more sensitive to temperature loss, implying a stronger C sink under warming.