A synthesis on the spatial patterns and driving factors of water-holding capacity of forest litter layer across China

Abstract

Forest litter layers play a crucial role in regulating hydrological processes and conserving ecosystem water, yet their spatial patterns and key drivers at regional scales remain unclear. By analyzing data from 1062 sampling sites across China using machine learning, we identified the distribution and controlling factors of forest litter mass, litter water-holding rate (LWHR), and litter water-holding amount (LWHA). Our findings reveal that (1) the mean storage of undecomposed and semi-decomposed litter was 6.2 and 10.3 t ha- 1, respectively, with a mean LWHR of 247.8 % and LWHA of 34.3 t ha- 1; (2) LWHR varied significantly among forest types, being highest in deciduous forests (285.7 %) and lowest in evergreen needleleaf forests (223.5 %); (3) LWHA was greatest in deciduous needleleaf forests (59.7 t ha- 1) and lowest in bamboo forests (17.4 t ha- 1); (4) both LWHR and LWHA decreased with latitude, indicating regional differences in litter water retention; and (5) climate and topography were the primary drivers of litter water-holding capacity, influencing litter production, accumulation, and decomposition. Our findings provide a scientific basis for forest management strategies aimed at enhancing water conservation, particularly in regions vulnerable to climate change and water shortages. The results also offer a reference for global forest ecosystems, highlighting the importance of litter layers in sustaining water resources and informing policy decisions on forest conservation and watershed management