Seed Availability and Woody Plant Distributions in a Fragmented Landscape: Evaluation of a Dispersal Limitation Hypothesis

EPA Grant Number: U914751
Title: Seed Availability and Woody Plant Distributions in a Fragmented Landscape: Evaluation of a Dispersal Limitation Hypothesis
Investigators: McEuen, Amy B.
Institution: University of Michigan
EPA Project Officer: Broadway, Virginia
Project Period: January 1, 1995 through January 1, 1996
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1995) Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology


The main objective of this research project is to determine how different types of human fragmented landscape characteristics (fragment area, shape, presence of connections, orientation, overall spatial configuration, surrounding types of land use) impact ecosystems, with specific interest in their impacts on movement patterns. Human needs dictate that much of the landscape be utilized for agriculture, transportation, housing, urban centers, etc. It also is imperative, however, that natural systems remain minimally degraded and responsive to environmental change due to human dependencies on them and their products. The long-term objective of this research is to predict the types of landscape configurations needed to retain minimally degraded and responsive ecosystems over long timeframes.


The broad question to be addressed by this research is whether landscape fragmentation can impact ecosystem composition through changes in plant dispersal inputs (seed rain). Specifically, does fragmentation favor plants with certain dispersal strategies and through this impact ecosystems floral composition? Or does the small contribution of poorer dispersers (shorter distance dispersers) and their seeding saturation over time counter such potential effects? Some lines of evidence support the former hypothesis. Island biogeographers have found that islands are dominated by bird-dispersed plants while mammal-dispersed plants are virtually non-existent and wind-dispersed are rare. Similar patterns are found in floral composition of highly isolated (>200 km) terrestrial systems (Sugden, 1982). On the smaller spatial scale of isolated oak woodlots, Auclair and Cottam (1971) hypothesized that succession to black cherry (Prunus serotina), as well as dominance of other bird-dispersed understory species, was due to fragmentation impacts. Matlack (1994) found that understory flora migration rates (distance moved/time) of ingested and adhesive propagules were greater than wind dispersed, ant dispersed, or gravity dispersed propagules. The groups with lower migration rates also were found to have lower abundances in areas isolated from the propagule source. Such data indicate that studying fragmentation impacts in terms of differing dispersal mechanisms may be a fruitful area for future research.

Study of landscape-scale plant dispersal ecology will provide a much needed link in basic research between small-scale dispersal studies and paleoecological studies of long-term, broad-scale distributional change. This link is of critical importance for applied research. Studies of landscape-scale plant dispersal should reveal: (1) whether such movement can occur; (2) which species are more capable of such movement; and (3) what landscape features help facilitate such movement.

Supplemental Keywords:

fellowship, land use, ecosystem, landscape, plant dispersal., Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Habitat, Ecology and Ecosystems, landscape context, community composition, land use effects, plant diversity, anthropogenic stressors, ecological consequences, habitat fragmentation, environmental stress