LAUSR

To determine the contribution of overstory and understory flora on soil water content in typical forest plantations on the Loess Plateau, standard sampling plots were established in five pure Robinia pseudoacacia L. and five pure Pinus tabulaeformis Carr. plantations, together with five more plots in mixed forests of both species. The relationships between the overstory structure, herbaceous diversity, soil water, and nutrients were analyzed using statistical methods including feature, geostatistical, and Pearson’s correlation analyses. The results indicated that the topsoil moisture content of the pure forests (12.80% and 11.97%, respectively) was greater than that of the mixed forest (6.75%), but significantly lower than that of a grassland (26.97%). The canopy leaf area index (LAI), herbaceous Shannon-Wiener index, Simpson’s index, and total nitrogen (TN) were important factors controlling the distribution of soil moisture (the absolute values of their correlation coefficients were more than 0.5). The spatial heterogeneity of topsoil moisture was greatest in the pure Robinia pseudoacacia L. forests. It was found that appropriately increasing and decreasing the significant controlling factors, including LAI, herb diversity, and soil TN, could improve the soil moisture content and mitigate its spatial heterogeneity to improve the growth of vegetation on the Loess Plateau.