Linking microbial nutrient limitation and community composition to nitrogen mineralization in bamboo forest soil with phosphorus addition
摘要
P addition increased rates of net N mineralization and ammonification but not nitrification. P addition increased soil bacterial biomass, but did not change fungi biomass. Soil enzymatic stoichiometry and microbial P limitation were responsible for N mineralization.
The soil nitrogen (N) supply plays a core role in nutrient cycling, whereas phosphorus (P) is generally considered the limiting element of ecological processes in subtropical forests. However, the specific characteristics and regulatory mechanisms governing how P affects soil N mineralization remain incompletely understood. P fertilizer is often applied in bamboo forests, and we collected bulk soil and two types of rhizosphere soils (soils surrounding stump roots and rhizome roots, respectively) from a bamboo forest and conducted microcosm experiments with P addition (PA) to simulate the application of P fertilizer. The N mineralization and microbial and enzymatic parameters of the rhizosphere and bulk soils presented the same response to PA. PA increased the rate of net N mineralization and ammonification, suggesting that PA is beneficial to the N supply in the soil. PA increased the soil bacterial biomass but decreased the fungi:bacteria ratio. The soil enzyme C:N:P ratio indicated that the microbial community was subjected to P limitation. PA resulted in an increase in the enzyme C:P and N:P ratios and a decrease in the enzyme vector angle, suggesting alleviation of P limitation in the soil microbial community. Hierarchical partitioning and Pearson correlation analyses revealed that enzymatic stoichiometry and the vector angle were key regulators of soil N mineralization. These results indicate that PA can not only increase the concentration of soil P but also enhance the soil N supply in subtropical P-limited forests, primarily through changes in microbial nutrient limitation rather than in microbial biomass or community structure.