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2007 Harvard Forest REU Student Symposium Abstracts

Dunbar Carpenter - Smithsonian Conservation Biology Institute at the National Zoo

Landscape-scale Ecological Drivers of Alliaria Petiolata Invasion in Western Massachusetts


Alliaria petiolata (garlic mustard) is an herbaceous biennial herb that has was introduced to the New England landscape over a century ago. Recent work has shown that inter-regional differences in the herb's presence and performance exist in Western Massachusetts. Some of the discrepancy in performance may be explained by differences in land-use history, but ecological factors should also affect A. petiolata's distribution. Habitat fragmentation, geophysical attributes, and forest community structure are all likely to influence garlic mustard's invasion pattern. One-hundred-and-seventy-five 25 100 m roadside, forested plots across two ecoregions were visited in the summers of 2006 and 2007. A. petiolata presence and incursion distance, dominant canopy species, slope, and soil moisture were recorded. Additional data on vicinity to water, and road, forest, and land-cover edge density was obtained for each plot using GIS datalayers from MassGIS.

Different metrics of habitat fragmentation and geology appeared to have little correlation with A. petiolata presence or performance. But A. petiolata does show a propensity to invade mesic to hydric soils (chi-squared test, p = .04 for presence and incursion). The survey data also shows that A. petiolata does poorly in Quercus-dominated forests (p < .001 for presence and incursion), but does well in forests dominated by Acer sachrum and Fraxinus Americana (for both species p < .001 for presence). The prevalence of Quercus in one of the ecoregions, and F. Americana in the other, accounts for some of the interregional differences in A. petiolata presence. The prevalence of Quercus in historically less disturbed sites, and A. sachrum in historically more disturbed sites accounts for some of the differences in A. petiolata performance between sites with different land use histories. From this it can be concluded that A. petiolata is not likely to be limited by lack of available forest edge habitat, but that other ecological factors, particularly soil moisture and forest community composition, do appear to affect garlic mustard distribution, and are closely associated with the ecoregional and land-use history patterns of this invasive plant.

click for /symposium/A petiolata & soil moisture.pdf

click for /symposium/A petiolata & dominant tree species.pdf

click for /symposium/A petiolata & dominant tree species by ecoregion.pdf

click for /symposium/A petiolata & dominant tree species by luh.pdf

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