Characteristics of Dissolved Organic Matter in Alpine Mountain Soils and Its Effect on Riverine Dissolved Organic Matter Export
The soil layers in permafrost regions store a large amount of organic carbon.However,the understanding of the influence of dissolved organic matter(DOM)in permafrost and seasonally frozen ground on the DOM characteristics of riverine output is still unclear due to limited existing studies on the characteristics of soil organic matter in permafrost and seasonally frozen ground and their differences in alpine catchments.To understand the distributions,and controlling mechanisms of dissolved organic matter in the soil of alpine catchments on aquatic DOM,this study collected soil samples of permafrost and seasonally frozen ground in the Hulugou catchment in the northeastern part of the Tibetan plateau and analyzed the soil organic carbon(SOC),dissolved organic carbon(DOC)content,spectral characteristics of DOM,and its biodegradable dissolved organic carbon(BDOC).Then,DOM characteristics in soils were compared with those from different water bodies at different seasons.The study reveals significant differences between permafrost and seasonally frozen soils in terms of dissolved organic carbon(DOC)biodegradability and microbial activity.Permafrost soils have higher soil organic carbon(SOC)but lower DOC,and their dissolved organic matter(DOM)is less humified and aromatic compared to seasonally frozen soils,where biodegradable DOC(BDOC)proportions are higher.The findings indicate that soil hydrological traits in cold mountain areas significantly influence soil organic matter,highlighting soil moisture as a critical factor.In permafrost areas,shallow soil DOM crucially affects river water DOC concentrations and composition.In contrast,seasonal permafrost zone soils have less direct influence on changes in stream DOC concentration and composition,with hydrological conditions shaping DOM's output features in water bodies.This research is crucial for understanding carbon cycling under permafrost degradation in cold mountain regions,condensed into a comprehensive summary within the specified word limit.
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