Multivariate analyses of the influences of water chemistry and habitat parameters on the abundances of pond-breeding amphibians

We surveyed 104 potential amphibian-breeding sites in northwest Indiana for the presence and abundance of amphibians, habitat parameters, and water chemistry. Linear regression was used as an exploratory analysis, and stepwise multiple regression and ANOVA were used to model factors that best explained amphibian species richness, abundance, and number of years with breeding populations. The most important breeding site factors among those studied were wetlands with semi-permanent hydrology, levels of dissolved chloride, silica, hardness and alkalinity, standing waters that were not ditches, wetlands without agriculture within 200 m, the number of hydrology types within one kilometer, the number of wetlands within 400 m, and biotic interactions within the amphibian community. Minor factors included the presence of ammonia, turbidity, low phosphates, low detergents and pH level; wetlands with wooded upland habitats <200 m, palustrine wetland habitats, surface area of the wetland, and percentage of the wetland covered by emergent vegetation.