Physical controls on the spatial and temporal biogenic gas dynamics in two subtropical wetland ecosystems in Florida

The spatial and temporal distribution of biogenic gas accumulation and release within peatland soils and their controls (i.e. both physical and environmental) remain highly uncertain. While several recent studies show the importance of the pore structure when defining gas dynamics, and particularly when modeling rapid gas releases (i.e. ebullition), it is unclear how different ecosystems (and particularly for subtropical systems) may show differences on such dependence. The study presented here investigates the spatial and temporal variability in biogenic gas accumulation and release in two 38-liter peat monoliths from two different wetland ecosystems in central Florida (pine flatwoods and emergent wetlands) at the laboratory scale. An array of non-invasive hydrogeophysical methods (using ground-penetrating radar, GPR) was combined with gas traps, time-lapse cameras, and direct measurements (i.e. porosity and bulk density) to explore gas content variability (i.e. build-up and release) within the peat matrix over a period of five months. The results show that specific physical soil properties for different types of wetland ecosystems play a critical role at controlling the dynamics of gas accumulation and release from peat soils. Furthermore, these differences are consistent with results on soils from other studies within similar ecosystems. This work has implications for better understanding how different types of ecosystem in subtropical systems may contribute differently to the production, accumulation, and release of greenhouse gases.