Wetland Biogeochemical Responses to Predicted Climate Change Scenarios

Wetlands are one of the world's largest known carbon sinks while comprising only a small amount of the Earth's surface. However, the amount of carbon sequestered by wetlands is shrinking as droughts and human disturbance increases. Carbon in wetlands is stored through the contrast of decomposition and sedimentation of organic matter and absorption of CO2 from the atmosphere by soil microbes. Understanding how changing hydrological regimes and increased wildfires will affect wetland soil and microbial processes is important in the face of predicted climate change for future wetland conservation practices. Specifically, I seek to understand the response of southeastern coastal plain wetland soils to the interaction of prescribed burns and variable hydrological conditions through the use of large-scale experimental ponds. By manipulating wetland flood duration, I was able to compare wetland soils that 1) were continuously dry, 2) were continuously flooded, or 3) were flooded and allowed to gradually recede in combination with prescribed burns prior to all flooding. I predicted that wetland soils and soil microbial biomass would respond positively to recede treatments compared to dry and flooded treatments and burned wetlands would have higher microbial biomass than not burned. Immediately following the burn and prior to flooding, I recorded a reduction in soil microbial biomass nitrogen, soil pH, and soil C:N. When assessed, soil microbial biomass carbon was found to be higher in both flooded and receding treatments compared to dry with the prescribed burn having no effect for the duration of the study. Results suggest that the prescribed burn was not intense enough to have lasting effects on wetland soils, though the addition of nutrients post-burn can take time to process through the system. Soil microbial biomass estimates were opposite to my predictions, suggesting that the amount of disturbance the soils experience is a more important driver of microbial biomass than optimal conditions for microbes (i.e., ...