Importance of active layer freeze-thaw cycles on the riverine dissolved carbon export on the Qinghai-Tibet Plateau permafrost region

PeerJ

article

Chunlin Song¹  Genxu Wang¹  Tianxu Mao³  Xiaopeng Chen⁴  Kewei Huang¹  Xiangyang Sun¹  Zhaoyong Hu¹ 

[1] Institute of Mountain Hazards and Environment, Chinese Academy of Sciences;University of Chinese Academy of Sciences;Guizhou University;Shanxi Agricultural University

关键词: DIC;    DOC;    Riverine carbon;    Biogeochemistry;    Qinghai-Tibet Plateau permafrost;    Active layer;   

DOI  :  10.7717/peerj.7146

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

The Qinghai-Tibet Plateau (QTP) is experiencing severe permafrost degradation, which can affect the hydrological and biogeochemical processes. Yet how the permafrost change affects riverine carbon export remains uncertain. Here, we investigated the seasonal variations of dissolved inorganic and organic carbon (DIC and DOC) during flow seasons in a watershed located in the central QTP permafrost region. The results showed that riverine DIC concentrations (27.81 ± 9.75 mg L−1) were much higher than DOC concentrations (6.57 ± 2.24 mg L−1). DIC and DOC fluxes were 3.95 and 0.94 g C m−2 year−1, respectively. DIC concentrations increased from initial thaw (May) to freeze period (October), while DOC concentrations remained relatively steady. Daily dissolved carbon concentrations were more closely correlated with baseflow than that with total runoff. Spatially, average DIC and DOC concentrations were positively correlated with vegetation coverage but negatively correlated with bare land coverage. DIC concentrations increased with the thawed and frozen depths due to increased soil interflow, more thaw-released carbon, more groundwater contribution, and possibly more carbonate weathering by soil CO2 formed carbonic acid. The DIC and DOC fluxes increased with thawed depth and decreased with frozen layer thickness. The seasonality of riverine dissolved carbon export was highly dependent on active layer thawing and freezing processes, which highlights the importance of changing permafrost for riverine carbon export. Future warming in the QTP permafrost region may alter the quantity and mechanisms of riverine carbon export.

【 授权许可】

CC BY