2000 Progress Report: Effects of Forest Fragmentation on Community Structure and Metapopulation Dynamics of AmphibiansEPA Grant Number: R827642
Title: Effects of Forest Fragmentation on Community Structure and Metapopulation Dynamics of Amphibians
Investigators: Johnson, Lucinda , Boone, Randall , Gross, John , Johnson, Catherine
Current Investigators: Johnson, Lucinda , Boone, Randall , Breneman, Dan , Gross, John , Johnson, Catherine , Olker, Jennifer H.
Institution: University of Minnesota - Duluth , Colorado State University
EPA Project Officer: Packard, Benjamin H
Project Period: December 1, 1999 through November 30, 2002
Project Period Covered by this Report: December 1, 1999 through November 30, 2000
Project Amount: $769,623
RFA: Ecological Indicators (1999) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Ecosystems
The overall goal of this research is to quantify the effects of forest fragmentation on amphibian community structure and population dynamics in vernal pool ecosystems. Specific objectives are to: (1) quantify the manner and extent to which forest fragmentation influences amphibian community structure; (2) assess the extent to which regional and local-scale indices reflect fundamental structural properties of vernal pool habitats and their biotic communities and, conversely, the extent to which amphibian community structure reflects local and landscape properties; and (3) develop predictive models to quantify the extent to which forest fragmentation influences the metapopulation dynamics of woodland amphibians and predict the consequences of landscape change on these metapopulations.
Over the past year, our research has focused on study site selection and collection of field and spatial data. Site selection was completed in April 2000, and included 38 sites in six wetland clusters. Two clusters each, one located in unfragmented woodland habitat and one in a more fragmented landscape, were selected in three areas: Wrenshall, Grand Rapids and Duluth, Minnesota. The fragmented clusters in these areas also represent differing levels of land use: low and high-intensity agriculture and urban development.
Calling surveys were conducted and field data (including water quality and macroinvertebrate sampling) collected during three surveys in 2000; invertebrate samples are being sorted and identified in the laboratory. Rainfall and wetland water level data also were collected on a daily basis at the eight Wrenshall pools, and detailed vegetative sampling was completed for all sites. More than 5600 amphibian captures were recorded during the 2000 field season, including 4301 individuals comprising seven anuran and two salamander species. Over 3400 wood frogs (primarily metamorphs) were captured in the drift fences around the Wrenshall wetlands, weighed, measured, individually marked and released; >100 blue-spotted salamanders were given wetland-specific marks and released. Toes that were clipped as part of the mark-recapture process were preserved in 70 percent alcohol for potential genetic analysis at a later date.
Collection of pertinent GIS (landscape) data for the study region, including land use, land cover, hydrography, roads, soils, Quaternary geology, and wetland (NWI) coverage, was initiated. Low-level infra-red aerial photos also were acquired for photo interpretation. These data will be used to characterize the landscape structure within a 5-km radius around each wetland, and will be incorporated into the metapopulation model structure.
Initial plans for modeling amphibian movements were solidified during a month-long effort as part of the first year of the project. A literature review was conducted, and relevant information was incorporated in a draft amphibian dispersal model, using raster-based spatial data layers read into a Microsoft Visual Basic 6.0 program called ?IMove.' In the model, vernal pools are metapopulations, with animals moving into and out of each metapopulation. The dispersing amphibians react in an integrated way to different spatial layers of information (e.g., spectral images representing differences in cover, elevation gradients, and distances to water). Metapopulation dynamics are emergent properties flowing from the movements of amphibians within and between vernal pools.
In the coming year, we will continue to compile and summarize landscape-level metric data. Satellite imagery also will be acquired to cover all study sites and enhance our land cover database. Landscape structure will be assessed for concentric buffers around each wetland and wetland cluster for use in spatial analyses to identify potential relationships between landscape metrics and amphibian community structure. Amphibian community data, along with on-site chemistry, light regime, and biotic surveys will be conducted at all sites again in 2001, with an increased effort made to capture adult and metamorphosing amphibians at the Duluth and Grand Rapids sites. We also will continue our mark-recapture efforts in Wrenshall over the next 2 years to assess the movement patterns of amphibians within and between study sites.
Modeling efforts goals in the second year are to locate and adapt an existing hydro-period model for vernal pools, since it appears that the extent of time that vernal pools hold water is critical in understanding amphibian metapopulation dynamics in Minnesota. We anticipate using weather, soils, and topographical data to roughly estimate hydro-period for each of the vernal pools in the study. That submodel will be merged with the draft amphibian dispersal model, and progress made toward finalizing it. Adequate field data will be available in the second year to allow us to merge those results with information from the literature, and calibrate the model.