Identifying the areas most vulnerable to a species' invasion within a habitat or region is crucial to managing and minimizing that species' eventual effect. The exotic annual grass Microstegium vimineum often occurs in the greatest density along disturbed corridors, such as waterways and trails, within otherwise undisturbed forests. We tested the hypothesis that such linear features within forests are correlated with invasion patterns. We surveyed linear transects along intermittent streams and foot trails through eight upland forests of different ages, as well as control transects within each forest that were distant from any type of linear feature. We documented significantly larger and denser patches of M. vimineum along transects in young forests than those in old stands. Streams and trails were similarly more invaded than control transects, and M. vimineum was distributed much more patchily away from such corridors. Isolated individual patches of M. vimineum (along neither streams nor trails) demonstrated the potential to expand at approximately 1 m over 1 y, although 11% of plants appeared farther than 2 m from their parent patch. Although germinants appeared downslope of the parent patch two to four times more frequently than upslope, the mean distance of spread was equivalent in both directions. Control efforts should focus on excluding the species from corridors that could allow entry, particularly in older forests.
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1 January 2012
Patterns of Patch Colonization and Expansion In the Non-Native Annual Grass Microstegium vimineum (Poaceae)
Jonathon W. Schramm,
Joan G. Ehrenfeld
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Rhodora
Vol. 114 • No. 957
January 2012
Vol. 114 • No. 957
January 2012
colonization
deciduous forest
dispersal corridors
historical effects
Microstegium vimineum
patch expansion
trails