Differences in available phosphorus in temperate and subtropical forest soils

Soil P availability is influenced by the acid phosphomonoesterase (ACP) activity, microbial biomass P (MBP), pH, and other soil properties. To date, there is no clear understanding about how the enzyme catalytic efficiency (Vmax/Km) and the abundance of the phoC and phoD genes that encode ACP and alkaline phosphomonoesterase (ALP) influence the available P contents at different depths in temperate and subtropical forest soils. We investigated how the soil enzyme kinetic parameters, phoC and phoD gene abundance, pH, total P contents, and other soil properties influenced the P availability in soils from a temperate forest (ChangBai Mountain) and a subtropical forest (QianYanZhou Plantation). The results showed that the DNA contents and the ACP and ALP activities were positively correlated with the available P contents in the temperate forest soil. The phoC and phoD gene abundance and the ALP activity were positively correlated with the available P contents in the subtropical forest soil. The ACP-Vmax/Km and DNA contents were positively correlated with the available P contents in topsoil (0–10 cm). The total P contents, pH, MBP, and ACP-Vmax/Km in subsoil (10–30 cm) were positively correlated with the available P contents. A structural equation model showed that DNA content had the greatest effect on the soil available P in temperate forest soil, and phoC and phoD gene abundance had the greatest effect on the soil available P in subtropical forest soil. The mechanism of H+ dissolution affected the P availability through low pH in the topsoil and weathering in the subsoil. Overall, these findings provided an improved understanding about how the catalytic efficiencies of ACP and ALP and the phoC and phoD gene abundance, influenced the P availability in temperate and subtropical forest soils at different depths. We also gained insights into how the P availability was affected by H+ dissolution and the parent material in topsoil and subsoil, respectively.