Soil bacterial community structure and extracellular enzyme activities under different land use types in a long-term reclaimed wetland

Abstract

This study was conducted to investigate shifts in the bacterial community structure and soil enzyme activities during long-term reclamation of different land use types in a freshwater wetland. Illumina 16S rRNA gene amplification and sequencing and soil extracellular enzymes were used to evaluate changes in bacterial community structure and potential function under four different land use types after 38 years of reclamation: abandoned wetland (AW), vegetable field (VF), pond sediment (PS), rice field (RF) and natural wetland (NW). Although bacterial rRNA gene alpha diversity remained unchanged, the bacterial community composition changed significantly under different land uses according to hydrological conditions. Under drying-wetting cycle conditions, RF harbored a similar bacterial community composition as NW, with Acidobacteriales, Holophagae, Planctomycetes, and Spirochaetae being dominant in both. Additionally, AW and VF as upland soil had significantly higher abundance of Gemmatimonadates and Actinobacteria. The composition of permanently flooded soil (PS) had unique features and significantly enriched levels of Chlorobi. The shifts in bacterial community structure were mainly driven by soil moisture content, as well as total organic C and N. However, variations in potential enzyme activities were better explained by soil properties than microbial community composition, suggesting high plasticity of the resident microbial community to environmental conditions. Rice field harbored a similar bacterial community structure as natural wetland, while the responses of enzyme activities for all land use types differed significantly. The distributions of bacterial community might be influenced by hydrology, while extracellular enzyme activities were closely related to soil properties. Our results suggest that the function of the active microbial community should also be considered in environmental risk models as indicators of ecosystem conversion caused by land use and anthropogenic activity.