Wetland restoration efforts aim to enhance the structure and function of degraded and damaged wetlands. Unfortunately, restoration techniques often alter a site's soil habitat and plant community structure, which affect the activity and composition of microbial communities. Microbial community structure and activity, as a function of soil texture and plant inputs, were studied in soils collected from a restored and a natural tidal freshwater wetland for a period of nine weeks. We expected that increasing the clay content of restored soils from 13% to 20% and 30% would increase soil C retention via sorption and reduce the carbon dioxide (CO2) and methane (CH4) emissions. To elucidate the role of plant inputs in shaping the microbial community and function, plant litter with contrasting C-to-nitrogen (N) ratios were added to soils. We hypothesized that a greater portion of plant leaf-C from the nutrient-poor plant, Phragmites australis, would be mineralized to CO2 and CH4 than the nutrient-rich plant, Peltandra virginica. We also expected P. virginica would support a more abundant and diverse microbial community than P. australis. Unexpectedly, we found that increasing the clay content of restored soils only marginally reduced the total amount of C partitioned as CO2 and CH4. The nutrient-rich plant, P. virginica, emitted more CO2 and CH4 than the nutrient-poor plant, P. australis. Furthermore, clay and plant leaf litter amendments had a greater impact on the size, diversity, and composition of the microbial population in restored wetlands soils than natural. Overall, we found that increasing clay content in a restored wetland will likely have a limited effect on soil C retention. We also discovered organic matter amendments to restored wetlands significantly altered the underlying structure of the microbial community but not for natural soils, suggesting greater diversity may lead to a more stable, resilient microbial community.
Read the article in Soil Biology and Biochemistry.