Effects of plantation types and patterns on rainfall partition in soil in a mid-subtropical region of China

Aims Mixed-species plantations are generally thought to increase soil carbon stocks, but it is unclear whether they can enhance soil water-holding capacity. By quantifying the contribution of rainwater to soil water (CRSW) following three different scales of rainfall events in Pinus massoniana and Schima superba monoculture plantations and a mixed P. massoniana and S. superba plantation, we aimed to examine the variations in CRSW and influencing factors for different plantations. Methods Stable hydrogen isotope compositions of rainwater, soil water and groundwater were analyzed to assess the CRSW of three plantations following three rainfall events in a subtropical monsoon region in China. We further used regression analysis to quantify the relative importance of canopy openness, litter characteristics, soil physical properties and root biomass to the CRSW. Results The CRSW in the P. massoniana monoculture plantation and mixed plantation was higher than that in the S. superba monoculture plantation following the three rainfall events. No significant difference in the CRSW was found between the P. massoniana plantation and the mixed plantation within nine days following the 8.7 mm rainfall event. Furthermore, the CRSW was significantly higher in the mixed plantation than in the two monoculture plantations within 11 days following the 15.3 mm and 36.9 mm rainfall events. The most important factors affecting the CRSW were canopy openness and root biomass after the 8.7 mm rainfall event, whereas root biomass and litter characteristics acted as the primary regulatory factors after the 15.3 mm rainfall event. Under the 36.9 mm rainfall event, dry weight and saturation moisture capacity within the semi-decomposed litter layer had the greatest influence on the CRSW. Conclusion Mixed-species plantations in humid subtropical regions have a higher capacity to intercept and maintain heavy rainfall than their respective monoculture plantations, and thus can enhance their adaptation to extreme rainfall events, as well as after frequent droughts.