Soil carbon and microbial communities at mitigated and late successional bottomland forest wetlands

The practice of wetland mitigation has come into question during the past decade because the relative capacity of the mitigated wetlands to perform normal wetland functions is mostly unknown. In this study, we wanted to determine whether soil microbial communities were significantly different in early successional mitigated wetlands (<10 years) (ES) compared to late successional bottomland hardwood forest wetlands (LS) due to differences in soil properties, such as carbon quality and storage and water-holding capacity. Carbon storage in litter and soil was 1.5 times greater in LS wetlands than ES wetlands. Soil water-holding capacity was significantly greater in LS wetlands and was related to soil organic C content (r²=0.87, p-value=0.0007). Gravimetric water content was a moderately strong predictor of microbial respiration (r²=0.55-0.61, p-value=0.001-0.0004) and microbial biomass (r²=0.70, p-value=0.0019). Anaerobic microbial groups were enriched in soils from LS wetlands in both the dry and wet seasons, which suggested that LS soils were wetter for longer periods of the year than ES soils. The capacity of these wetlands to support anaerobic microbial processes depends on soil water retention characteristics, which were dictated by organic matter content. As an integrator of microbial growth conditions in soils, determination of microbial community composition by phospholipid fatty acid (PLFA) analysis may be an important new tool for monitoring successional development of compensatory mitigation wetlands.