Soil moisture dynamics and response to rainfall under two typical vegetation covers based on HYDRUS-3D

In this study, based on the continuous measurement of soil water content and meteorological parameters, the HYDRUS-3D model was used to simulate the dynamic changes of soil moisture in different soil layers (1050 cm soil depth) under two typical vegetation covers [alluvial wetland forest (AWF) and ungrazed Bahia grassland (UBG)] in wet and dry seasons in the Alafia River Basin, Florida. Model performance was evaluated using several statistical criteria. Water balance and parameter sensitivity were analysed to indicate the adaptability of the model to the study area. Furthermore, soil moisture variation was assessed under different rainfall levels and its relationships with vegetation type, root biomass and soil physical characteristics were quantitatively and qualitatively analysed. Results showed that the correlation degree between the measured and simulated values of soil water content in the wet and dry periods was higher in the AWF than in the UBG. The water reserves of the UBG were relatively stable. The most sensitive parameters of the model to simulate soil moisture were saturated water content and pore size index. There were significant differences in soil water variation between the two vegetation types. The effect of precipitation on soil moisture was higher under AWF than under UBG.