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

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

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

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.

Original languageEnglish (US)
Article numbere2021JG006406
JournalJournal of Geophysical Research: Biogeosciences
Volume127
Issue number1
DOIs
StatePublished - Jan 2022

Bibliographical note

Funding Information:
This work was facilitated in part by support provided by the following programs: This study was funded by the Scientific Instrument Developing Project of the Chinese Academy of Sciences, Grant No. YJKYYQ20190012 and the National Natural Science Foundation of China (41501083). We acknowledge Opening Research Foundation of State Key Laboratory of Frozen Soil Engineering, Chinese Academy of Sciences (SKLFSE201812 and SKLFSE201702). Hanbo Yun acknowledges the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA19070504) and National Cryosphere Desert Data Center, Northwest Institute of Eco‐Environment and Resources, Chinese Academy of Sciences. Qing Zhu was supported by the Reducing Uncertainties in Biogeochemical Interactions through Synthesis and Computation (RUBISCO) Scientific Focus Area, which is sponsored by the Earth and Environmental Systems Modeling (EESM) Program under the Office of Biological and Environmental Research of the US Department of Energy Office of Science. Yang Qu thanks the School of Urban and Regional Science, East China Normal University (Research on Asian Water Tower Changes 13902‐412125‐20018/005). Wenxin Zhang was supported by the Swedish Research Council VR starting grant 2020‐0533 and the Swedish National Space Agency project grant 209/19 and Bo Elberling by the Danish National Research Foundation (CENPERM DNRF100). We would like to thank Yongzhi Liu, Guilong Wu, Ji Chen, and Guojun Liu for their tremendous help in collecting field data over all these years. Thanks to Professor Per‐Erik Jansson for providing assistance with the non‐growing season data analysis.

Funding Information:
This work was facilitated in part by support provided by the following programs: This study was funded by the Scientific Instrument Developing Project of the Chinese Academy of Sciences, Grant No. YJKYYQ20190012 and the National Natural Science Foundation of China (41501083). We acknowledge Opening Research Foundation of State Key Laboratory of Frozen Soil Engineering, Chinese Academy of Sciences (SKLFSE201812 and SKLFSE201702). Hanbo Yun acknowledges the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA19070504) and National Cryosphere Desert Data Center, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences. Qing Zhu was supported by the Reducing Uncertainties in Biogeochemical Interactions through Synthesis and Computation (RUBISCO) Scientific Focus Area, which is sponsored by the Earth and Environmental Systems Modeling (EESM) Program under the Office of Biological and Environmental Research of the US Department of Energy Office of Science. Yang Qu thanks the School of Urban and Regional Science, East China Normal University (Research on Asian Water Tower Changes 13902-412125-20018/005). Wenxin Zhang was supported by the Swedish Research Council VR starting grant 2020-0533 and the Swedish National Space Agency project grant 209/19 and Bo Elberling by the Danish National Research Foundation (CENPERM DNRF100). We would like to thank Yongzhi Liu, Guilong Wu, Ji Chen, and Guojun Liu for their tremendous help in collecting field data over all these years. Thanks to Professor Per-Erik Jansson for providing assistance with the non-growing season data analysis.

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.

Keywords

  • Tibetan Plateau
  • alpine steppe ecosystem
  • automatic chamber
  • carbon sink
  • eddy covariance
  • soil respiration

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