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

Abstract

[Objective] As the most active component in forest soil, dissolved organic matter (DOM) can not only be directly utilized by microorganisms, but also be the main carrier for the migration of C, N, P and other elements in the ecosystem. The migration process is influenced by the hydraulic interactions and dissolving processes driven by throughfall. [Methods] Using soil column microcosm in situ culture to analyze the effects of forest throughfall on the dynamics of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and dissolved organic phosphorus (DOP) across varying layers of sandy red soil during the rainy season. The study focused on a subtropical evergreen broad-leaved forest with rainfall as a control. [Results] (1) During the rainfall season, the DOM input of throughfall into soil increased significantly compared with rainfall(p<0.01). The concentrations of DOC, DON and DOP increased by 37.00%, 93.47%, and 85.12%, respectively, and the fluxes of DOC, DON and DOP also increased by 20.76%, 49.93%, and 61.55%, respectively. However, there was no significant difference in output fluxes after passing through the 40 cm deep soil, indicating a strong capacity of the soil to absorb DOM from throughfall. (2) Compared to rainfall, throughfall reduced the C/N and C/P ratios of the soil surface by 29.19% and 26.00%, respectively, without significantly affecting N/P ratios. After passing through 40 cm of soil, throughfall reduced the input C/N, C/P and N/P ratios of the soil by 19.35%, 13.35% and 7.45%, respectively. The increase in DOM in throughfall was mainly due to the absorption of DON and DOP in the canopy, while the decrease in soil DOM was mainly concentrated in DOC and DOP. (3) Soil DOC and DOP showed a reduction in interception, while DON showed an increase in enrichment. Throughfall increased the interception of DOC and DOP in the 0-40 cm soil by 39.93% and 72.42%, respectively, and significantly reduced the release of DON by 32.37%. [Conclusion] These results demonstrate that throughfall in a subtropical evergreen broad-leaved forest can promote the input of DOM and facilitate its uptake at different soil depths, with implications for the sustainable management of ecosystems.

Keywords

• subtropical forest
• sandy red soil
• dissolved organic matter
• canopy interception
• rainfall