Effects of Throughfall on the Migration of Soil Dissolved Organic Matter in Subtropical Evergreen Broad-leaved Forest

Dissolved organic matter (DOM) is a highly dynamic component in forest soils, prone to migration. However, little information has well addressed the processes of soil DOM migration driven by throughfall, although it is well known that throughfall could be closely related to DOM migration in subtropical forests. Therefore, we used a soil column microcosm in situ to analyze the effects of throughfall on the migration processes of DOM, calculated from dissolved organic carbon in a subtropical evergreen broad-leaved forest. Over one-year incubation, throughfall retained three times more DOM in forest soils than rainfall. Specifically, throughfall inputted 29.72% more DOM into the soil than rainfall, but 21.18% less DOM outputted from soil driven by throughfall compared with rainfall. Moreover, these retentions mainly happened in the wet season, while DOM loss was common in the dry season, possibly due to understory microclimate-altered soil structure. Relative to rainfall, throughfall enhanced humification, resulting in a greater tendency for DOM in soils to accumulate simple DOM rather than being further transformed. The results take an insight into understanding the increase of soil DOM driven by throughfall compared with rainfall, and highlight the importance of forest canopy in reducing the loss of soil DOM.