MODELING HYDROLOGY AND FISH OCCURRENCE IN ISOLATED WETLANDS TO IDENTIFY WETLAND COMPLEXES FOR MANAGEMENT

It is widely recognized that depression wetlands are important habitats for a range of flora and fauna, and that their conservation will be essential in protecting biological diversity in the southeast. However, a wetland-by-wetland approach to conserving and managing depression wetlands is not likely to be an effective strategy because hydroperiods and biological communities vary greatly among wetlands and among years within wetlands. Because wetland associated species are often adapted to specific hydroperiods and sets of biological interactions, and may require adjacent uplands to complete their life cycles, a collection or landscape of wetlands encompassing natural variation in hydroperiod and biotic conditions will be required. Operationally, land managers currently have little guidance in identifying and prioritizing isolated wetland landscapes for conservation purposes. We used information on the occurrence of surface water and fishes in 91 wetlands on the Upper Coastal Plain of South Carolina to generate classification tree models of hydroperiod and fish occurrence based on wetland habitat conditions and landscape position. We then hierarchically clustered wetlands based on their geographic location and assessed diversity in predicted hydroperiod and fish presence/absence within clusters to identify the spatial extent of wetland landscapes that would provide protection of the range of hydroperiod and fish presence/absence conditions found in these systems. The size of wetland landscapes identified as encompassing diversity of hydrological and predatory conditions among wetlands often closely corresponded to the area of small stream watersheds, but not all small watersheds contained the complete range of variation. Our approach should provide land planners with guidance in selecting management units for isolated wetlands.