高寒山区土壤碳是全球冻土碳库的重要组成部分，以溶解相从陆地侧向输出到河流是该地区土壤碳输出的重要途径，而以往研究主要集中在多年冻土区，对季节冻土区关注较少.为探讨季节冻土区河流溶解性碳的输出规律、影响因素及其作用机制，以位于青藏高原祁连山北麓黑河上游的季节冻土山区——红泥沟小流域为研究区，通过对河水中溶解性有机碳（DOC）和溶解性无机碳（DIC）浓度与通量的连续观测，结合河水中稳定同位素丰度及流域内气象、水文、地温等观测数据，发现在冻土消融前期（春末），流域出口河水中DOC和DIC浓度较高但通量较低；在冻土消融后期（夏季），河水中DOC和DIC浓度较低但通量较高；河水中DOC和DIC浓度在消融后期总体呈下降趋势，但低流量期的浓度比高流量期略有上升.研究表明：对以红泥沟小流域为代表的季节冻土山区，消融前期溶解性碳输出的主控因素仍是冻土特征及动态，但在消融后期则变为水文输入特征主控，以细粒残坡积物为主的薄层含水层和广泛发育的冻融扰动地貌也对其有重要影响，导致河流中DOC浓度高于青藏高原其他地区的报道值.

Soil carbon storage in alpine regions is an important component of the global frost carbon pool. Lateral carbon export from terrestrial ecosystems to rivers in dissolved phase is an important pathway for soil carbon export from alpine catchments. Previous studies on dissolved carbon export from alpine catchments have focused on permafrost areas, and less attention has been paid to seasonal frost areas. To explore the patterns, influencing factors and mechanisms of dissolved carbon export through rivers in seasonal frost areas, we selected the Hongnigou catchment at the northern flank of the Qilian Mountains on the Qinghai-Xizang Plateau as the study area, and we made continuous observations of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations and fluxes in river water. Combining the observed data of stable isotope abundance in river water and meteorology, hydrology, and ground temperature in the catchment, it is found that: (1) during the early thawing period in late spring, the riverine DOC and DIC at the outlet of the catchment were high in concentration but low in flux; (2) during the late thawing period in summer, the riverine DOC and DIC were low in concentration but high in flux; and (3) both DOC and DIC concentrations in the river showed an overall decreasing trend in summer, but slightly increased during low flow periods compared to high flow periods. The study shows that for the alpine catchments underlaid by seasonal frost, represented by the Hongnigou catchment, the dissolved carbon export is mainly influenced by frost characteristics and dynamics during the early thawing period. However, during the late thawing period in summer, it becomes dominated by hydrological input characteristics. During this period, the thin aquifers consisting mainly of fine-grained residual deposits and the widespread freeze-thaw disturbed landforms also have significant impacts, resulting in a higher riverine DOC concentration than that reported in other areas of the Qinghai-Xizang Plateau.