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Historic and current influences on habitat invasibility in a mosaic landscape: Cape Cod National Seashore.
Von Holle, Betsy*,1, Foster, David1, Motzkin, Glenn, 1 Harvard Forest, Harvard University, Petersham, MA
ABSTRACT- Effects of non-native species are a hazard to global biodiversity, second only to habitat destruction. For informed management decisions, we must determine factors that contribute to ecological resistance to biological invasion. Habitat invasibility to plant invaders was investigated in the highly resistant Cape Cod ecosystem through a spatially-explicit study of historical disturbances and current environmental and biotic properties of 20 x 20m field plots, randomly located across the landscape. These 352 plots were within natural areas, half within Cape Cod National Seashore, MA. This region experienced intensive land use during European settlement of the area, followed by large-scale reforestation in the last century and fire suppression in the last 60 years. Historic disturbances, current vegetation, edaphic properties and other environmental conditions were determined for each plot using historic and field methods. These factors were assessed for their influence on exotic species richness and cover with multiple linear regressions and canonical correspondence analyses. The most influential factors for non-indigenous plant cover and richness were current soil nutrient conditions. Plots that had been plowed or burned in the past did not have significantly greater richness of non-indigenous species. While land use history in Cape Cod National Seashore is a strong determinant of native community assemblages, this is not the case for non-native species in natural areas. The resistance of these natural areas may be due to the harsh conditions provided by the depauperate soils in this area.
Key words: resistance , invasibility, landscape