Stoichiometric imbalances and the dynamics of phosphatase activity and the abundance of phoC and phoD genes with the development of Cunninghamia lanceolata (Lamb.) Hook plantations

Abstract

Soil phosphatase and P-cycling functional genes, such as phoC and phoD, are crucial factors in regulating terrestrial P cycling, especially in highly weathered subtropical and tropical soils. Soil element stoichiometry (especially available C:N:P by measuring dissolved organic C (DOC):available N (AN):Olsen P plays an essential role in biogeochemical P cycling, but how it affects phosphatase activity and the abundance of phoC and phoD genes following afforestation is unclear. Here, we investigated how soil C:N:P stoichiometry affected the dynamics of soil phosphatase activity and the abundance of phoC and phoD genes in an age sequence of 6-, 12-, 18-, 25-, 32-, and 49-year-old Chinese fir plantations. The results showed that the phosphatase activity and the abundance of phoC gene were overall higher in 18- and 25-year-old plantations than in the other four plantations. The abundance of phoD gene gradually increased with stand age. Phosphatase activity significantly and positively correlated with DOC:Olsen P and AN:Olsen P ratios, but not with DOC:AN ratio. Soil phosphatase activity significantly positively correlated with phoC gene abundance, but not with phoD gene abundance, indicating that the phoC gene abundance is the dominant predictor of the microbial functional potential for secreting phosphatase. Further analysis suggested that the ratios of DOC:Olsen P and AN:Olsen P, total N, DOC, AN, Olsen P, and microbial biomass C were the main predictors of phoC gene abundance and that DOC:AN, total P, AN, Olsen P, and microbial biomass C were the main predictors of phoD gene abundance. These findings together highlight the importance of soil available element stoichiometry regulating microbial functional genes, with potential implications for subtropical and tropical biogeochemical processes and for understanding how soil available C:N:P stoichiometry regulates P biotransformation.