Amphibian occurrence and wetland characteristics in the Puget Sound Basin

Abstract

We studied the pattern of amphibian distributions within 19 wetlands of the Puget Sound Basin in King County, Washington State from 1988 through 199 I. Amphibian richness was compared to wetland size, vegetation classes, presence of bullfrog and fish predators, hydrologic characteristics of water flow, fluctuation, and permanence, and land use. Low velocity flow and low fluctuation were correlated with high species richness. Seasonal persistence of water was unrelated to species richness. Wetland size, distance to other wetlands favorable for breeding, fish and bullfrog predators, and the number of vegetation classes found at a wetland were unrelated to total number of species. Increasing mean water-level fluctuation and percent watershed urbanization were correlated with low species richness.Small and structurally simple wetlands often have high value amphibian habitat, and traditional reliance on wetland size and broad vegetation classes without site-specific studies should be avoided when assessing habitat value for amphibians.

Evaluating perturbations and developing restoration strategies for inland wetlands in the Great Lakes basin

“…Perturbations to wetlands, such as changes in water regimes and nutrient levels, may favor the expansion of invasive taxa, such as Typha or Phalaris, resulting in competitive exclusion of plant species . Changing water regimes associated with stormwater impacts have been shown to limit reproductive potential of some amphibians in the Pacific Northwest (Richter and Azous 1995). Since multiple stressors tend to impact wetlands and their consequences are both direct, indirect, and cumulative, the lack of documentation on causes for losses of biodiversity is not surprising.…”

“…Wetland plant biodiversity has both local and regional components, and the ability to sustain diversity of plant guilds, such as sedge meadow and wet prairie species with limited seed production and dispersal capabilities, likely depends on the density of natural wetlands in a region (Galatowitsch and van der Valk 1996a). Similarly, habitat quality for animal metapopulations using wetlands during all or part of their life cycle depends not only on the habitat quality of individual wetlands (Richter and Azous 1995), but also upon a wetland density sufficient to facilitate recolonization following local extinctions (Gibbs 1993, Smith andHellmund 1993). Assessment of status and goals for critical wetland densities for maintenance of habitat and biodiversity should be made at a planning unit scale appropriate for the dispersal range of biodiversity elements of concern.…”

Identification of habitat controls on northern red-legged frog populations: implications for habitat conservation on an urbanizing landscape in the Pacific Northwest

“…Lack of association may reflect R. aurora's ability to lay multiple egg masses on one oviposition brace (per observation). Other research identifying negative associations with wetland size and R. aurora may reflect the secondary effects of exotic predators, i.e., smaller wetlands are less likely to maintain fishes or bullfrogs (Richter and Azous 1995;Adams 1999;. Additionally, R. aurora spend little time seasonally in wetlands, so finding a relationship with wetland size may not be a sensitive variable to measure.…”

Distribution Patterns of Lentic-Breeding Amphibians in Relation to Ultraviolet Radiation Exposure in Western North America

“…None of these lentic-breeding species are known to be declining in Olympic. However, R. cascadae has declined at the southern tip of its range in California (Fellers and Drost 1993), and surveys conducted in Washington for B. boreas found this species to be less common than expected (Richter and Azous 1995;Adams and others 1998Adams and others , 1999Adams and others , 2001. Few data are available for Oregon, but the numbers of B. boreas in several long-studied locations have not declined (Olson 2001).…”