Wetlands are important sinks in the global carbon cycle as flooded, anaerobic conditions retard organic matter decomposition, thus increasing soil carbon storage. To increase understanding of wetland ecosystem function and evaluate the impacts of hydrological restoration on carbon storage, this study assessed the relationship between water levels and organic soil depth at the Disney Wilderness Preserve (DWP). This 4,654-hectare former ranch, now managed by the Nature Conservancy, underwent hydrological and ecological restoration from 1994 to 2012 to mitigate Disney and airport development. The restored site contains 1,416 hectares of wetlands situated at the headwaters of the Everglades. For restoration and monitoring purposes these wetlands were assigned to 24 hydrologic units (HUs), each of which has an instrumented well for continuously measuring water level and several manual monitoring wells that were read once per month. Initial monitoring data included “organic soil depth” determined by pushing a probe into the soil to resistance along multiple transects of each HU. We used this existing monitoring data to test the hypothesis that long-term (12-20 year) average water depth measured at the manual monitoring wells would be strongly correlated with organic soil depth measured along the sites’ original monitoring transects.
Results/Conclusions
There was a significant (p < 0.001) positive correlation between organic soil depth and average water depth from the manual monitoring wells in most habitat types at DWP, but the model had poor explanatory power (R2 = 0.049). This model had weaker explanatory power than a model previously run on the correlation between organic soil depth and average water depth measured at a single continuous monitoring well in each HU (R2 = 0.089). These results may suggest that monthly measurements are not as accurately predicting long-term average water depth as more frequent but less widespread water elevation monitoring, which might more accurately predict soil carbon storage. Other variables, such as vegetation type, may also be stronger predictors of soil carbon storage than water depth. How well organic soil depth relates to, or can serve as a proxy for, actual soil carbon storage and accumulation is unknown. Determining soil carbon density along the established transects not only will provide a better understanding of carbon storage in these systems, but also may reveal that average water depth has a stronger relationship to soil carbon storage than it does to physically-based measurements of organic soil depth.