Effects of Landscape Composition and Wetland Fragmentation on Frog and Toad Abundance and Species Richness in Iowa and Wisconsin, U.S.A.

Abstract

Management of amphibian populations to reverse recent declines will require defining high‐quality habitat for individual species or groups of species, followed by efforts to retain or restore these habitats on the landscape. We examined landscape‐level habitat relationships for frogs and toads by measuring associations between relative abundance and species richness based on survey data derived from anuran calls and features of land‐cover maps for Iowa and Wisconsin. The most consistent result across all anuran guilds was a negative association with the presence of urban land. Upland and wetland forests and emergent wetlands tended to be positively associated with anurans. Landscape metrics that represent edges and patch diversity also had generally positive associations, indicating that anurans benefit from a complex of habitats that include wetlands. In Iowa the most significant associations with relative abundance were the length of the edge between wetland and forest ( positive) and the presence of urban land (negative). In Wisconsin the two most significant associations with relative abundance were forest area and agricultural area ( both positive). Anurans had positive associations with agriculture in Wisconsin but not in Iowa. Remnant forest patches in agricultural landscapes may be providing refuges for some anuran species. Differences in anuran associations with deep water and permanent wetlands between the two states suggest opportunities for management action. Large‐scale maps can contribute to predictive models of amphibian habitat use, but water quality and vegetation information collected from individual wetlands will likely be needed to strengthen those predictions. Landscape habitat analyses provide a framework for future experimental and intensive research on specific factors affecting the health of anurans.

Metacommunity dynamics of amphibians in years with differing rainfall

“…In our case, landscape variables had only a minor effect on the assembly of communities. In a less fragmented landscape like our study area, forests can moderate the negative effects of intensive agriculture (Hartel et al 2010;Knutson et al 1999). Sheltered corridors with moist microclimate and wet substrate are very important during dispersal, especially for recently metamorphosed juveniles to avoid dehydration (Gibbs 1998).…”

Uso de fragmentos florestais por anuros (Amphibia) de área aberta na região noroeste do Estado de São Paulo

“…A temperatura elevada e a baixa umidade encontrada em áreas abertas devem ser limitantes para anfíbios, que apresentam alta taxa de perda de água por evaporação e pouca habilidade de dispersão (Rothermel & Semlitsch 2002). Neste contexto, fragmentos florestais são hábitats relativamente menos perturbados em comparação com áreas agrícolas e urbanas, e proporcionam corredores para migração de anuros entre sítios de reprodução e áreas de refúgio, alimentação e estivação (Laan & Verboom 1990, Knutson et al 1999, Weyrauch & Gubb Jr. 2004.…”

Restored Agricultural Wetlands in central Iowa: Habitat Quality and Amphibian Response

“…Previous studies have found that wetland characteristics alone are insufficient to explain variations in amphibian species richness and that landscape characters (e.g., surrounding land use) are also important (Hecnar and MCloskey 1996;Knutson et al 1999). In our study, restored and reference wetlands are situated in an agriculturallydominated landscape, and are surrounded by similar buffers of perennial vegetation.…”