The Influence of Landscape Composition on the Biotic Community of Constructed Depressional Wetlands

Abstract

To increase wetland acreage and biodiversity, state agencies constructed more than 220 depressional wetlands throughout Delaware. We investigated effects of landscape composition within 1,000 m and 5,000 m of 20 Kent County, Delaware constructed wetlands on their avian, macroinvertebrate, and vegetative communities. Using digital orthophotography and geographic information system (GIS), we quantified agriculture, early successional, forest, development, freshwater wetlands, roads, and streams within concentric buffers. We also calculated distance to nearest forest, wetland, and paved road edge from the wetland's center. In 2004 and 2005, we surveyed the biotic communities and regressed richness and diversity values against landscape variables. Proximity of nearest forest edge was the most important variable in explaining avian and vegetative richness and diversity. We detected negative relationships with distance to nearest forest and bird richness, bird diversity, total plant richness, facultative wetland plant cover, and native, exotic, and obligate wetland plant richness and cover. Furthermore, bird richness and diversity increased with forest area within 1,000 m and bird diversity increased with forest area within 5,000 m. To optimize biodiversity, managers should consider proximity to forest for wetlands constructed in agricultural landscapes.