Document: JUS-3-67-7

Historical versus hyrdologic controls on early successional dynamics in beaver meadows.

WRIGHT, J.P* ^1,2, C.GJONES ² and A.SFLECKER ¹

Cornell University, Ithaca, NY 14853, USA ¹
Institute of Ecosystem Studies, Millbrook, NY 12545, USA ²

Abstract:
In the central Adrirondacks, beaver are extremely abundant and, by building dams, create a unique habitat type in the riparian zone. Because the meadows that form after beaver pond abandonment are composed primarily of plant species not found elsewhere in the landscape, ecosystem engineering by beaver is responsible for a significant increase in species richness at the landscape scale. This increase in richness at the landscape scale is also due to the considerable variability in species richness (from 21 to 62 species in equivalent sampling areas) and composition between different meadows. Differences in the composition of meadows could arise from variability in seed bank composition due to differences in site history or from variability in seed bank emergence due to drainage rates. Factors that affect seed bank composition, such as pond age and distance from seed sources are potentially influenced by the population dynamics of the ecosystem engineer whereas hydrologic features of a meadow are largely independent of the number of beaver in a landscape. Sediment was collected from 6 active beaver ponds and placed in mesocosms under high and low drainage rates. After one growing season, site had a significant effect on species richness (p = 0.001), but was only a minor determinant of community composition. The high drainage treatment had significantly higher species richness than the low drainage treatment (p < 0.001), and drainage rate was the primary determinant of community structure. These results suggest that hydrologic factors such as drainage rate are the major determinants of early successional dynamics in beaver modified patches, and factors more directly influenced by the population dynamics of beaver are of less importance in generating variability at the between meadow scale.

Keywords: species richness, ecosystem engineers, seed bank

This abstract is being presented at: 11:00 AM in session:
Oral Session #45: Water Relations in Shrubs and Annuals.