PS 49-265 - Soil microbial community structure and function are enhanced by soil organic carbon additions in created wetlands

Abstract: Wetlands are ecologically important, providing essential ecosystem services such as biogeochemical cycling, carbon sequestration, and habitat provision. Many of these services are the result of the unique microbial communities found in wetlands. Restoration has been adopted to compensate for both intentional and unintentional degradation and destruction of wetlands. Unfortunately the success rate in achieving functional equivalence of restored systems with natural wetlands is low. To improve wetland conservation, a better understanding of the biotic community structure and biotic-abiotic relationships in developing wetlands and how management strategies may promote successful restoration outcomes is needed. Using the metagenomic approach of 16S rRNA amplicon sequencing, we aim to better understand the role of microbial communities as drivers of wetland biogeochemical cycling and succession. In this study we experimentally added readily available municipal leaf litter compost to three created wetlands and compared relative changes in the soil microbial communities in amended and non-amended soil to those of nearby natural reference wetlands. The three wetland groups were located in the Finger Lakes Region of Western New York State and included both forested and emergent wetlands. Each of the wetlands differed in hydrology and vegetation composition. We also measured soil nutrients, carbon and physical characteristics along with vegetation community composition. Overall, leaf litter compost increased organic matter and nutrients in treated plots in comparison to untreated control plots in the same created wetland, and appeared to accelerate development of soil structure towards that of natural wetlands. However, soil amendments appeared to promote development of a unique soil microbial community structure unlike either the created controls or natural wetlands. Relative abundance of Phylum showed that Firmicutes (and the Class Bacilli) was highest in the leaf litter compost addition plots at all sites, and both Verrumicrobota and Desulfobacterota were lowest in the compost addition. Microbial metabolic functions were assessed using FAPROTAX. In spite of the distinct microbial community, functional diversity in the compost amended plots fell between the reference and control plots, suggesting a shift towards the reference state. In particular, dark hydrogen oxidation and phototrophy found in the treated plots were more similar to the natural reference state at one of the wooded wetland groups. These results suggest that soil amendments may assist with development of ecosystem functions and services, but that the underlying ecosystem structure may vary in significant ways from wetlands without exogenous amendments.