Print PageDynamic hydrology in wetland ecosystems mediates oxygen and nutrient availability, affecting the structure of microbial communities. To examine the relationship between landscape and local factors on microbial community composition, we surveyed total bacterial and denitrifier community composition along with landscape (regional climate variables and proportion of wetland, developed, and agricultural land surrounding a wetland) and local soil factors (moisture, organic matter, inorganic N, pH, redox status) at 27 restored wetlands in Illinois. Based on these survey results, we identified that changes in redox status and soil moisture in these ecosystems strongly influence microbes at the wetland level. To further explore the influence of local abiotic factors within wetlands, microbial structure-function relationships were compared along an upland-to-wetland gradient at two natural and two restored wetlands. Soil chemistry and microbial community composition of denitrifiers and ammonia oxidizers (assessed by molecular analysis of functional genes) were analyzed along with potential denitrification and nitrification activity. The contribution of environmental factors to microbial community variability was determined using PERMANOVA.
Results/Conclusions
Precipitation and growing degree-days significantly contributed to variation in overall bacterial community composition but not denitrifier community composition. In addition, soil pH strongly contributed to among- and within- wetland variation in total bacterial and denitrifier communities. Different soil factors representing soil nutrient status and redox conditions were also important to bacterial and denitrifier communities within wetlands. Abiotic differences (e.g., soil moisture, pH) along the hydrologic gradient produced contrasting assemblages of denitrifiers and ammonia oxidizers within wetlands. Further, different combinations of soil factors influenced community patterns of denitrifiers and ammonia oxidizers along hydrologic gradients. Potential denitrification and nitrification rates were not predictably controlled by soil moisture along the hydrologic gradient at each site. With greater understanding of proximal roles of the environment on microbial communities, we can improve our ability to predict the response of microbially-mediated nutrient cycling activities to support desired microbial functions.
