Warming and Increased Respiration Have Transformed an Alpine Steppe Ecosystem on the Tibetan Plateau From a Carbon Dioxide Sink Into a Source

Summary, in English

Cold region ecosystems store vast amounts of soil organic carbon (C), which upon warming and decomposition can affect the C balance and potentially change these ecosystems from C sinks to carbon dioxide (CO₂) sources. We quantified the decadal year-round CO₂ flux from an alpine steppe-ecosystem on the Tibetan Plateau using eddy covariance and automatic chamber approaches during a period of significant warming (0.13°C per 10 years; and 0.18°C in the non-growing season alone: 1st October to next 30th April). The results showed that ongoing climate change, mainly warming within the topsoil layers, is the main reason for the site’s change from a sink for to a source of CO₂ in the atmosphere. Non-growing-season ecosystem respiration accounted for 51% of the annual ecosystem respiration and has increased significantly. The growing seasons (1st May to 30th September) were consistent CO₂ sink periods without significant changes over the study period. Observations revealed high-emission events from the end of the non-growing season to early in the growing season (1st March to fifteenth May), which significantly (p < 0.01) increased at a rate of 22.6 g C m⁻² decade⁻¹, ranging from 14.6 ± 10.7 g C m⁻² yr⁻¹ in 2012 to 35.3 ± 12.1 g C m⁻² yr⁻¹ in 2017. Structural equation modeling suggested that active layer warming was the key factor in explaining changes in ecosystem respiration, leading to significant changes in net ecosystem exchange over the period 2011–2020 and indicated that these changes have already transformed the ecosystem from a CO₂ sink into a source. These results can be used to improve our understanding of the sensitivity of ecosystem respiration to increased warming during the non-growing period.

• Author: Hanbo Yun; Jing Tang; Ludovica D’Imperio; Xiaobo Wang; Yang Qu; Licheng Liu; Qianlai Zhuang; Wenxin Zhang; Qingbai Wu; Anping Chen; Qing Zhu; Deliang Chen; Bo Elberling
• Department/s: Dept of Physical Geography and Ecosystem Science; MERGE: ModElling the Regional and Global Earth system; BECC: Biodiversity and Ecosystem services in a Changing Climate
• Publishing year: 2022-01
• Language: English
• Publication/Series: Journal of Geophysical Research: Biogeosciences
• Volume: 127
• Issue: 1
• Links: http://dx.doi.org/10.1029/2021JG006406
• Document type: Journal article
• Publisher: Wiley
• Topic: Physical Geography
• Keywords: alpine steppe ecosystem; automatic chamber; carbon sink; eddy covariance; soil respiration; Tibetan Plateau
• Status: Published
• ISBN/ISSN/Other: ISSN: 2169-8953