The Hydrology and Ecology of Isolated Wetlands
Isolated wetlands are critically imperiled ecosystems; by virtue of being small and not hydrologically connected (at least not obviously so), they are under-valued by our regulatory framework for wetlands protection. However, they are particularly well situated to confer to all of us the many services that wetlands provide, and because they are small and only intermittently flooded, they provide a critically important habitat setting, supporting far more than their share of threatened and rare taxa.
The many services that accrue from these wetlands might lead one to think that they are particularly well studied. In fact, processes occuring in isolated wetlands are only now becoming a research priority. It's in that vein that my lab's collective effort in this area was started. As we started working in these settings, we discovered that they are also useful model systems for wetlands more broadly.
Our work in isolated wetlands has taken three primary tacks. The first and foremost has been on numerically describing their hydrology, and in particular using a novel suite of methods to develop very high resolution water budget estimates, including direct empirical estimates of evapotranspiration based in the White (1932) method. This has revealed a critical insight: isolated wetlands, despite lacking surface connectivity, maintain flow in surface water drainage systems via their tempering effect on surficial groundwater levels. The detailed understanding of site hydrology that has been made possible by these methods permits far better resolved estimation of the ecosystem services that these wetlands provide, including water storage, C sequestration, and regional hydrologic buffering.
A second aspect of our work in isolated wetlands has focused on assessing the response of vegetation to anthropogenic stressors (water quality, fire exclusion, hydrologic modification, exotic species). Our work has focused most recently on trying to quantify the temporal stability of bioassessment metrics since these are typically calibrated based on one detailed site visit, despite intrisinc temporal variation in community composition.
Finally, we have become very interested recently in understanding how and why microtopography develops in wetlands. Our work suggests that the fraction of a wetland basin that is "hummocks" is remarkably well constrained (ca. 20% of the area). Moreover, the spatial arrangement of hummocks appears to be over-dispersed. Ongoing work is focused on quantifying these patterns over a range of site ages, and enumerating the improved primary production that is made possible at the site level with the presence of microtopography.
