W&L Research on the Effects of Road Building on Forest Habitats Awarded Three-Year NSF Funding

February 10, 2003

The National Science Foundation (NSF) has awarded a $374,754 grant to Washington and Lee University biologists David M. Marsh and Paul R. Cabe for their continuing study on how the building of roads is increasingly fragmenting threatened forest habitats.

The three-year NSF grant will enable the W&L faculty members and their undergraduate students to intensify their field surveys, field experiments and genetic analyses to determine how different types of roads affect the density, dispersal and gene flow among terrestrial salamanders in forest habitats.

The W&L research in ecology and conservation biology is central in producing data for state and federal management decisions related to road building in forests and to amphibian population declines in those areas. Fragmentation affects amphibian and animal populations by degrading habitat near forest edges and by reducing the species' dispersal rates among remaining forest habitat patches.

Terrestrial salamanders are an important component of temperate forest ecosystems, thus making the W&L research useful to evaluate forest health.

"Most previous studies of these effects have focused on habitat fragmentation by land uses that affect a large proportion of the landscape, such as logging and urban development," said Cabe and Marsh, assistant professors in W&L's biology department.

"Only recently have biologists begun to examine the effects of roads, which constitute a much smaller population of the landscape but have the potential to create both edge effects and strong barriers to animal dispersal. Our preliminary data show significant reductions in salamander densities and changes in habitat characteristics near forest roads," Cabe and Marsh said in their NSF grant proposal.

The grant, a substantial award to a liberal arts institution without graduate-level science programs, will allow the W&L research team to test several specific theories in their ongoing research. Their work will focus on the following hypotheses:

1) Salamanders are less abundant near forest roads. The W&L researchers will use replicated transect surveys to determine the effects of roads on patterns of abundance for red-backed salamanders (P. cinereus) and slimy salamanders (P. glutinosus). They will determine whether density or condition of animals changes with distance from forest roads, and whether these patterns differ among species.

2) Roads cause edge effects on salamander populations by reducing soil moisture and the availability of rocks, moss and trees on the forest floor. Marsh will use a factorial addition experiment to determine whether lack of suitable cover or reductions in soil moisture appear to cause observed reductions in salamander density near forest edges. They will also use a combination of correlative tests and demographic models to test the alternative hypothesis that edge effects are caused by traffic related mortality of juvenile and adult red-backed salamanders.
3) Roads constitute barriers to dispersal for terrestrial salamanders. The W&L faculty-student research group will use displacement experiments to determine whether roads of different types affect red-backed salamanders' dispersal ability. By comparing return rates of salamanders moving across roads to those of salamanders moving through forest, the W&L group will determine the extent to which different types of roads constitute barriers to movement.

4) Roads reduce gene flow among populations of terrestrial salamanders. The two faculty researchers will use microsatellite markers to analyze patterns of genetic differentiation among populations of red-backed salamanders. They will then compare sets of paired populations that are separated by a road or only by continuous forest. This experiment's design will be repeated across several types of roads to determine the extent to which these various roads affect gene flow.

The W&L project is the first to use a combination of detailed surveys, field experiments and genetic analysis to study the effects of roads on animal populations in fragmented habitats. The NSF-backed project also provides an array of research and training opportunities for undergraduates across the fields of population ecology, genetics and geography.

For interviews, contact Marsh at 540-458-8176, marshd@wlu.edu, or Cabe at 540-458-8894, cabep@wlu.edu.

Media requests to join the W&L research team in the field should be directed to Ruth S. Intress, media relations director, at 540-458-8955, rintress@wlu.edu.