Seasonal variations of soil microbial biomass within two typical wetland areas along the vegetation gradient of Poyang Lake, China

- Soil microbial biomass was determined along the vegetation gradient in two typical wetlands.
- Soil microbial biomass was characterized with high variations among vegetation communities.
- Dish-shaped pit wetland had greater capacity active carbon sink compared to Delta wetland.
- A weak relationship was found between soil microbial biomass and vegetation community biodiversity.

Poyang Lake, a wetland area of critical ecological importance, is characterized by dish-shaped patterns of vegetation along the lakeshore. In this study, we intensively investigated seasonal and spatial variations of soil microbial biomass (SMB) within three representational vegetation communities in the two dominant types of wetlands within Poyang Lake. The results showed high levels of SMB carbon (SMBC) and SMB nitrogen (SMBN) among the vegetation communities within both types of wetlands. The highest concentrations of SMBC and SMBN were found in spring and autumn in the Phragmites community, the lowest in the Phalaris community. Compared to the delta wetland, the dish-shaped pit wetland was found to have higher levels of SMBC and SMBN within the same vegetation type. Interestingly, variations of SMB were also significantly and positively correlated with vegetation biomass both in spring and autumn. Moreover, we found variations of SMB to be consistently correlated with soil bulk density, soil nutrient conditions and elevation. However, contrary to seasonal tendency, we detected relationships between SMB and community biodiversity, indicating a hidden interaction between these aspects in Poyang Lake.