Kourtev, P., Ehrenfeld, J., and
Huang, W. (1998). Effects of exotic plant species on soil
properties in hardwood forests of New Jersey. Water, Air
& Soil Pollution, 105: 493-501.
Two exotic plant species, Berberis thunbergii and
Microstegium vimineum, recently have invaded deciduous
hardwood forests in the Northeast. We examined changes in soil
properties that may be associated with this invasion in three
parks in northern New Jersey. In each park, we collected soil and
vegetation data along transects that were established across
heavily infested areas and extended into uninvaded forest. The
data were analyzed statistically by ANOVA and Canonical
Correspondence Analysis (CCA). Significant differences were found
between invaded and uninvaded plots in both soil and vegetation
characteristics. Invaded areas have fewer oaks (Quercus
spp.) in the canopy, and lack the native understory shrubs
(Vaccinium spp.). The pH of soils in the invaded areas is
significantly higher flan in the uninvaded areas, and the litter
and organic horizons are thinner. The data cannot show that the
exotic species have caused these changes. However, the occurrence
of contrasting soils in adjacent areas of native vegetation, with
no evidence of differences in land-use history between areas,
suggests that such a cause-and-effect relationship exists. We
propose a feedback loop involving the exotic plants, and the
presence of earthworms to explain these dramatic soil differences.
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