资源环境科技发展态势分析平台

The flux of terrestrial carbon across land-water boundaries governs the overall carbon balance of landscapes and the ecology and biogeochemistry of aquatic ecosystems. The local consequences and broader fate of carbon delivered to streams is determined by the overall composition of carbon inputs, including the balance of organic and inorganic forms of carbon. Yet, our understanding of how hydrologic fluxes across different land-water interfaces regulate carbon supply remains poor. We used seven years of data from three boreal catchments to test how different land-water interfaces (i.e., forest, wetland, and lake) modulate concentration-discharge (C-Q) relationships for dissolved organic carbon (DOC), carbon dioxide (CO₂), and methane (CH₄), as well as its balance (e.g., DOC:CO₂). Seasonal patterns in concentrations and C-Q relationships for individual carbon forms differed across catchments. DOC varied between chemostasis and transport limitation in the forest catchment, between supply limitation and chemostasis in the wetland catchment, and was persistently chemostatic in the lake outlet stream. Carbon gases were supply limited overall, but exhibited chemostasis or transport limitation in forest and wetland catchments linked to elevated flow in summer and autumn. Unique C-Q relationships for individual forms reflected the properties of different interfaces and underpinned changes in the composition of lateral carbon supply. Accordingly, DOC dominated the carbon flux during snowmelt, whereas gas evasion during other times of the year. Integrating the C-Q dynamics of individual carbon forms helps understand the shifting composition of lateral export, and thus predict how hydrologic changes may alter the fate of carbon supplied to streams.