Plant species and season influence soil physicochemical properties and microbial function in a semi-arid woodland ecosystem

Abstract

This research investigated the effects of woody plant identity and season on soil physicochemical properties and microbiological function in the semi-arid Zagros forest, one of the old-growth semi-arid oak forests in the world. Soil sampling was conducted beneath the canopy of six woody (tree and shrub) species in spring and winter. Microbial variables analysed included soil basal respiration (BR), microbial biomass C and N (MBC and MBN), microbial entropy index (MIE), substrate induced respiration (SIR) and enzymatic activities (i.e., urease and alkaline phosphatase). Soil physicochemical properties were also analysed and included pH, electrical conductivity (EC), available calcium and magnesium (Ca2+ and Mg2+), organic carbon (OC), total nitrogen (Ntot), lime, water content (WC), bulk density (BD), clay, silt and sand. Results demonstrated significant differences among the woody species (Pseudo-F = 56.31; p = 0.001), season (Pseudo-F = 97.37; p = 0.001) and their interaction (Pseudo-F = 2.96; p = 0.005) for the matrix of microbiological soil parameters. Differences were species-specific for shrubs and trees with a marked effect for tree species such as Quercus brantii. Microbial parameters were consistently higher in spring when higher temperature and lower moisture were recorded. Soil OC, Ntot, BD, and WC were important drivers of the soil microbial function. Our results evidenced a strong effect of season and plant species on soil physicochemical and microbiological soil properties in a semi-arid forest ecosystem. Higher values of microbiological soil parameters, including urease and phosphatase activities, were recorded for tree species during spring season.