19 Aug 2022
19 Aug 2022
Status: this preprint is currently under review for the journal BG.

Variations of carbon flux at different time scales in a semi-fixed sandy land ecosystem in Horqin Sandy Land, China

Yayi Niu1,3,4, Yuqiang Li1,2,3,4, Wei Liu1,3, Xuyang Wang1,3,4, and Yun Chen1,3,4 Yayi Niu et al.
  • 1Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
  • 2Key Laboratory of Strategic Mineral Resources of the Upper Yellow River, Ministry of Natural Resources, Lanzhou 730000, China
  • 3University of Chinese Academy of Sciences, Beijing 100049, China
  • 4Naiman Desertification Research Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Tongliao 028300, China

Abstract. Sandy land is an important part of terrestrial ecosystem, which has a substantial impact on maintaining global ecological health and security. However, there is still a scarcity representative studies of climate change’s effect on the carbon fluxes (NEE: net ecosystem CO2 exchange; Reco: ecosystem respiration; GPP: gross primary productivity). Eddy covariance technique was used to determine carbon fluxes and climatic conditions in this ecosystem from 2017 to 2021. At an annual scale, the semi-fixed sandy land was found to be a net carbon release, the value of annual average NEE was 6.81 ± 36.35 g C m-2 yr-1. It functioned as a carbon source in dry years (2017 and 2020), but was a carbon sink in wet years (2019 and 2021) and a normal year (2018). At seasonal scale, according to the Random Forest, deep soil water content (SWC80) and photosynthetic photon flux density had a great impact on NEE and GPP, whereas shallow and deep soil water (SWC10 and SWC80) dominated Reco. At a monthly scale, the multiple stepwise regression showed that soil temperature, precipitation (PPT) and SWC were the dominant environmental factors. At an annual scale, correlation analysis showed that total annual PPT was negatively correlated with NEE. Our results illustrate the importance of climate variations for the NEE, Reco, and GPP at different time scales in arid and semi-arid areas. They also highlight the importance of water availability (the pattern and intensity of PPT and SWC at different depths) on regional and global carbon cycles.

Yayi Niu et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-171', Anonymous Referee #1, 12 Sep 2022
  • RC2: 'Comment on bg-2022-171', Renee Prokopavicius, 15 Sep 2022

Yayi Niu et al.


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Short summary
Seasonal Reco was regulated by both shallow and deep soil water content (SWC80 and SWC10). PPFD and the soil water content at 80 cm regulated seasonal NEE and GPP variation. Rainfall (PPT), soil temperature, and SWC regulated monthly carbon-flux variation. Inter-annual variation of NEE was modulated by the total annual PPT. Annual variation of GPP was regulated by PPFD and SWC80. At all time scales, water availability controlled ecosystem carbon fluxes.