Effect of fertilization on the temporal dynamics of soil microbial community and multifunctionality along subtropical forest succession
Soil microbes play an important role in carbon (C) and nutrient cycling in forest ecosystems. However, the effect of chemical fertilization on temporal dynamic of soil microbial community and functions in different subtropical forest successional stages was not investigated. Here, we examined soil bacterial and fungal communities and multifunctionality (enzyme and C resource metabolic activities) in a 4-year experiment of nitrogen (N) and phosphorus (P) addition in three growth seasons (April, August, and November) under two successional stages (young and mature) in a Chinese subtropical forest. The richness of total, saprotrophic and ectomycorrhizal (EM) fungi and total, oligotrophic and copiotrophic bacteria was significantly higher in April and August than in November, while the pathogenic fungal richness was significantly higher in combination of N and P fertilization compared to other fertilization treatments. The temporal analysis demonstrate that the community composition of total, saprotrophic and EM fungi and total bacteria in November, April and August, and oligotrophic bacteria in November was influenced by P fertilization, while that of pathogenic fungi was significantly influenced by N fertilization in November, April and August and copiotrophic bacteria by both N and P fertilization in November. In addition, the community composition of total and functional groups of fungi and bacteria significantly differed between November and April/August. Furthermore, the community composition of total and functional groups of fungi and total bacteria but not their functional group in different season were significantly differed between young and mature forest indicating soil bacteria and fungal groups vary in their functional relationship with forest age. Soil multifunctionality was influenced by fertilization and season but not by forest stage, and related to fungal community negatively but to bacterial community and richness positively. This study suggests that the temporal dynamics of fungal and bacterial community composition strongly influenced by P fertilization and forest stage while the temporal dynamics of soil mulitifunctinality influenced by N and P fertilization  in a subtropical forest succession.