A modified approach to model the hydrological effects of living moss and fallen leaves on carbonate-derived laterite in karst forests

Abstract

Due to recent vegetation restoration projects in karst mountainous areas of China, the living moss and litter layer play important roles in controlling soil water dynamics in karst forests. However, the underlying mechanisms of the effects of moss and the litter layer on soil water dynamics are still controversial. To explore the underlying mechanisms, we employ the CoreKarHydro model, capturing soil water content dynamics driven by evapotranspiration and influenced by living moss and fallen leaves. This model integrates surface changes' impact on evapotranspiration, categorizing the domain into: no cover (S), moss (SM), pine needles (SP), and both (SMP). Model validation employs the MOCOM-UA method, using diverse metrics (RMSE, R2, ACC, ED, KGE and SA) against lysimeter data with 4 moss biomass levels and 3 pine needle biomass levels. The results indicated: 1) The CoreKarHydro model exhibited reliable performance in simulating the soil water content curves, with an RMSE ranging from 1.49% to 4.21% and an R2 value ranging from 0.60 to 0.77. 2) Among the factors that influenced evaporation processes, soil hydraulic properties emerged as the most sensitive parameters, whereas the properties of the moss and pine needles played a relatively lesser role. 3) The impact of moss cover on evaporation processes varied depending on the soil texture and the stage of evaporation. Moss cover reduced evaporation loss in 8 out of 12 soil textures (loamy sand, loam, silt, silt loam, sandy clay loam, silty clay loam, sandy clay, and silty clay). On the other hand, moss cover increased evaporation loss in 4 out of 12 soil textures (sand, sandy loam, clay loam, and clay). This study contributes to the understanding of the mechanisms of coupled soil-moss(litter)-hydrological processes in karst areas.