Depthwise Soil CO2 Production Is Controlled by Freeze-Thaw Processes in a Tibetan Alpine Steppe

Cold ecosystems in regions of high-latitude and altitude with vast stores of soil organic carbon suffer strong freeze-thaw cycles, which can greatly affect soil CO2 release. However, on the Tibetan Plateau, where altitude is >4,000 m, it remains unknown how freeze-thaw processes regulate CO2 prod...

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Bibliographic Details
Published in:Journal of Geophysical Research: Biogeosciences
Main Authors: Zhang, Jianxin, Wei, Da, Hong, Jiangtao, Wang, Xiaodan
Format: Report
Language:English
Published: AMER GEOPHYSICAL UNION 2022
Subjects:
Soil CO2 production
freeze-thaw processes
Tibetan Plateau
alpine steppe
CARBON-DIOXIDE
TEMPERATURE SENSITIVITY
WATER-CONTENT
VERTICAL-DISTRIBUTION
MICROBIAL ACTIVITY
PERMAFROST CARBON
GRADIENT-METHOD
ORGANIC-MATTER
GAS-DIFFUSION
FROZEN SOIL
Environmental Sciences & Ecology
Geology
Environmental Sciences
Geosciences
Multidisciplinary
permafrost
Online Access:http://ir.imde.ac.cn/handle/131551/56432
https://doi.org/10.1029/2021JG006678
Description
Summary:Cold ecosystems in regions of high-latitude and altitude with vast stores of soil organic carbon suffer strong freeze-thaw cycles, which can greatly affect soil CO2 release. However, on the Tibetan Plateau, where altitude is >4,000 m, it remains unknown how freeze-thaw processes regulate CO2 production across the soil profile. In this study, we used the gradient method to explore impacts of freeze-thaw processes on depthwise soil CO2 production in an alpine steppe. We found almost all soil CO2 was produced in the root-zone layer (<30 cm), while the root-free layer (>30 cm) frequently alternated between being a source and sink of CO2 and thus acted largely as a buffer. The surface layer (0-15 cm) and subsurface layer (15-30 cm) had a similar CO2 production rate in the thawed period. However, during the freezing-frozen-thawing period, the subsurface layer consistently functioned as a weak CO2 source, although parts were trapped in frozen soil, resulting in a weaker CO2 sink in the surface layer. Soil CO2 production in subsurface layer is thus more sensitive to temperature variability compared with surface layer. Furthermore, our results suggest water content plays a more important role than temperature in regulating soil CO2 production. For the first time, our data set reveals the vertical production of CO2 within the seasonally frozen soils on the Tibetan Plateau, which will benefit understanding of belowground carbon processes and modeling of soil CO2 release in the region.

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