2001 Progress Report: Effects of Forest Fragmentation on Community Structure and Metapopulation Dynamics of Amphibians

EPA 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, 2000 through November 30, 2001
Project Amount: $769,623
RFA: Ecological Indicators (1999) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Ecosystems

Objective:

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.

Progress Summary:

Pertinent, available digital spatial data for the study region, including land use, land cover, hydrography, roads, Quaternary geology, soils and wetland (NWI) coverage, has been acquired, merged, and clipped for the study areas. Low-level, infrared aerial photos were acquired for the area within 5 km of each cluster, scanned, georeferenced, and used to visually interpret high-resolution land cover within 1 km of each site. These photos were used in conjunction with U.S. Geological Survey topographical maps and National Wetlands Inventory mapping to locate additional vernal pools (too small to identify accurately from photos alone) in the vicinity of study ponds. Four leaf-off, Landsat 7 satellite scenes have been acquired for fall 1999 and spring 2000 for the project study areas. Spring and fall leaf-off scenes were chosen to best map high and low water levels. An additional pair of leaf-on (5/31/200) scenes also was acquired to better classify upland land cover in the study area. Image classification is underway.

The investigators have completed the second year of field work at 37 study sites (6 wetland clusters in 3 geographically distinct pairs, each with 1 fragmented and 1 unfragmented cluster). Calling surveys were conducted and field data (including water quality and macroinvertebrate sampling) were collected during three surveys in 2000 and 2001. Pitfall traps and drift fences installed around the eight Wrenshall wetlands were checked daily (from April 17–August 27) for amphibians. Amphibians also were collected via minnow traps, activity traps or by hand at all other study sites during one of the three seasonal surveys. Captured amphibians were identified and examined for malformations prior to their release; wood frogs and salamanders were weighed, measured, and given a unique mark to detect recaptures. Small mammals incidentally captured in pitfall traps were released if alive, but if dead, were given to the Minnesota County Biological Survey for identification. Rainfall and wetland water level data were collected on a daily basis at all Wrenshall sites in association with the mark-recapture effort; water temperature was recorded daily throughout the season at all sites.

More than 12,000 individual amphibians were captured during the 2001 field season, including seven anuran and two salamander species (Table 1). Over 9,600 wood frogs were captured in the drift fences around the Wrenshall wetlands, including 253 recaptures from 2000 (approximately 7 percent of the individuals captured that year). While most of the 2001 recaptures (61 percent) occurred at their original year-2000 capture location, several individuals had moved between wetland clusters (> 1.5 km). More wood frogs were captured at all drift fence sites in 2001 than in 2000. However, metamorph dispersal in 2001, was lower for two of the three sites that produced metamorphs in 2000 (Figure 1); this decrease in wood frog productivity coincided with a shorter hydroperiod in those two sites. Dispersal of blue-spotted salamander metamorphs from these sites was similarly affected. Preliminary data were recently presented at two meetings attended by forestry and wetland managers (see below).

Table 1. Amphibians captured as part of the mark-recapture portion of the study, 2000-2001; recaptures are not included.

 
Township (location of study sites)
 
Wrenshall
Grand Rapids
Duluth
Species
2000
2001
2000
2001
2000
2001
Rana sylvatica
3,433
9,629
51
53
5
11
Ambystoma laterale
451
740
6
 
 
 
Bufo americanus
173
1,557
 
 
 
 
Plethodon cinereus
3
13
 
 
 
 
Hyla spp.
6
29
 
 
 
 
Pseudacris triseriata
8
102
2
 
 
 
Pseudacris crucifer
13
396
5
3
6
1
Rana clamitans
123
79
 
 
 
 
Rana septentrionalis
16
5
 
 
 
 
Notophthalmus viridescens
 
 
 
2
 
 
Total
4,226
12,550
64
58
11
12

It was determined that ephemeral pool hydroperiod is a critical variable in predicting the number of dispersing amphibians. Although hydroperiod is being measured at the study sites, long data records are required to accurately model metapopulation dynamics. Therefore, Boone modeled pool hydroperiod using typical hydrologic modeling methods of calculating water flow, although their application to vernal pools is not typical. The investigators’ model appears to predict hydroperiods reasonably, but validation with observed data is pending. Boone modified the metapopulation model IMOVE to apply to each of the three project study sites. The IMOVE program was modified to represent pools and accumulate dispersing individuals moving from one pool to another.

Figure 1.  Metamorph dispersal from vernal pool study sites in Wrenshall, MN, 2000-2001.

Future Activities:

In the coming year, the investigators will finalize land cover maps from the Landsat imagery and summarize landscape-level metric data at several spatial scales. Landscape structure will be assessed for concentric buffers around each wetland or wetland cluster for use in spatial analyses to identify potential relationships between landscape metrics and amphibian community structure. Amphibian surveys will be conducted at all sites again in 2002, with an increased effort made to capture amphibians at the Duluth and Grand Rapids sites. Mark-recapture efforts in Wrenshall will be continued to further document the movement patterns of amphibians within and between study sites. Additional field data to be taken in 2002, include woody debris and UVB measurements. Continuous and instantaneous recordings of UV will be performed at a subset of pools in the study area and related to the surrounding vegetation patterns and levels of fragmentation.

Metapopulation dynamics modeling using data gathered in the last two field seasons will be conducted this summer. The hydroperiod model, based on weather, soils, and topographical data, will be compared to 2000-2001 field data from study sites and refined if necessary. That submodel then will be merged with the draft amphibian dispersal model, and finalized.

Journal Articles:

No journal articles submitted with this report: View all 6 publications for this project

Supplemental Keywords:

ecological effects, sensitive populations, vulnerability, animal, stressor, indicators, aquatic, conservation, genetics, biology, ecology, monitoring, analytical, Midwest, EPA Region 5, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Ecology, exploratory research environmental biology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, Forestry, Ecological Effects - Environmental Exposure & Risk, Environmental Monitoring, Ecological Risk Assessment, Agronomy, Ecological Indicators, anthropogenic stresses, risk assessment, wetlands, ecological exposure, UV effects, aquatic biota , algae, frogs, landscape indicator, vernal pool ecosystems, amphibian, multiple spatial scales, regional scale, ecosystem indicators, multiscale assessment, community structure

Relevant Websites:

http://www.nrri.umn.edu/cwe/waterresources.htm Exit

Progress and Final Reports:

Original Abstract
  • 2000 Progress Report
  • Final Report