Effects of species mixtures on soil water storage in the semiarid hilly gully region

Mixed-species plantations are promoted to restore degraded ecosystems and improve soil quality worldwide. However, differences of soil water conditions between pure and mixed plantations are still controversial and how species mixtures affect soil water storage (SWS) was not well quantified. In this study, vegetation characteristics, soil properties and SWS were continuously monitored and quantified in three pure plantations (Armeniaca sibirica (AS), Robinia pseudoacacia (RP) and Hippophae rhamnoides (HR)) and their corresponding mixed plantations (Pinus tabuliformis-Armeniaca sibirica (PT-AS), Robinia pseudoacacia-Pinus tabuliformis-Armeniaca sibirica (RP-PT-AS), Platycladus orientalis-Hippophae rhamnoides plantation (PO-HR), Populus simonii-Hippophae rhamnoides (PS-HR)). The results found that SWS of 0–500 cm in RP (333.60 ± 75.91 mm) and AS (479.52 ± 37.50 mm) pure plantations were higher than those in their corresponding mixed plantations (p > 0.05). SWS in the HR pure plantation (375.81 ± 81.64 mm) was lower than that in its mixed plantation (p > 0.05). It is suggested that the effect of species mixing on SWS was species specific. Additionally, soil properties exerted more contributions (38.05–67.24 %) to SWS than vegetation characteristics (26.80–35.36 %) and slope topography (5.96–29.91 %) at different soil depths and the whole 0–500 cm soil profile. Furthermore, by excluding the effects of soil properties and topographic factors, plant density and height were particularly important to SWS (with standard coefficients 0.787 and 0.690 respectively). The results implied that not all the mixed plantations exhibits the better soil water conditions than the compared pure plantations, which was tightly related to species selected for mixing. Our study provides scientific support for revegetation technique improvement (structural adjustment and species optimization) in this region. [Display omitted] •Vegetation characteristics and soil properties were monitored in pure and mixed plots.•Effect of species mixtures on soil water storage was species specific.•Species mixtures did not always improve soil water conditions.•Soil properties exerted more contributions to the spatial variations in soil water.•Bulk density, capillary porosity and plant density were the dominant ones.