MODELING WETLAND FLORISTIC QUALITY CHANGE IN SPACE AND TIME IN THE PRAIRIE POTHOLE REGION OF THE UNITED STATES

The Prairie Pothole Region (PPR) landscape is known for its abundance of small wetlands formed by glacier retreatment; however, many of these wetlands have been drained for farm development. Restoration of wetland habitats in the PPR is an important activity of the U.S. Department of Interior (DOI) and U.S. Department of Agriculture (USDA) and generally involves plugging drains to restore hydrology and planting surrounding upland catchments to perennial cover. The wetlands in the PPR provide diverse ecosystem services, including carbon sequestration, groundwater recharge, nutrient retention, runoff and flood attenuation, water storage, contaminants filtering, and wildlife habitat provisioning. However, this list of benefits is not exhaustive and additional ecological services likely have been realized at local, regional, national, and even global scales. One of the ecological services that wetlands provide is the maintenance of diverse native plant communities. Floristic quality is a measure of the condition of these communities. Two common metrics of floristic quality are mean C and Floristic Quality Index (FQI). Mean C is the average coefficient of conservatism value (C) for all native species occurring in the area. C values are assigned by a panel of botanists with local plant knowledge and are based on each species’ likelihood to occur in a high quality natural area. FQI incorporates a measure of species richness derived from mean C and the number of native species present. Different sites can have the same mean C but different FQI scores, or vice versa. Therefore, it is useful to estimate both values. Although it is well known that the indicators of mean C and FQI can be used to assess floristic quality, these metrics are sensitive to climate fluctuations, and no model is available to quantify changes over large areas for this ecological service. In our research, we used the Wetland Continuum Conceptual Model (Euliss et al., 2004) to simulate the dynamics of floristic quality from landscape to regional scale in the PPR. Through this model, the mean C and FQI of a given wetland can be defined if three components are known: a) hydrologic relation to groundwater (groundwater of recharge, flow-through, and discharge derived from National Wetland Inventory (NWI) data); b) hydrologic relation to atmospheric water (drought to deluge derived from the Moisture Deficit Index (MDI) and Palmer Drought Severity Index (PDSI)); and c) predominant surrounding landscape within a wetland (derived from the National Land Cover Database (NLCD) 2001). The results of this model are being compared with field survey data collected in 18 wetlands at the USGS’s Cottonwood Lake Study Area for accuracy assessment. The next step of our research is to use our model to simulate the spatiotemporal change on floristic quality under three scenarios: 1) if 1/3 of the wetland disappeared (human drainage), 2) if all the potential wetlands are restored (wetland restoration); 3) if the two IPCC climate scenarios (A2 and B2) are adopted (climate change).