Patterns of Plant Invasions: A Case Example in Native Species Hotspots and Rare Habitats |
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Authors: | Thomas J Stohlgren Yuka Otsuki Cynthia A Villa Michelle Lee Jayne Belnap |
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Institution: | (1) Midcontinent Ecological Science Center, US Geological Survey, Fort Collins, CO 80523, USA;(2) Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, USA;(3) Canyonlands Field Station, US Geological Survey, 2282 S. Resource Blvd, Moab, UT 84532, USA |
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Abstract: | Land managers require landscape-scale information on where exotic plant species have successfully established, to better guide
research, control, and restoration efforts. We evaluated the vulnerability of various habitats to invasion by exotic plant
species in a 100,000 ha area in the southeast corner of Grand Staircase-Escalante National Monument, Utah. For the 97 0.1-ha
plots in 11 vegetation types, exotic species richness (log10) was strongly negatively correlated to the cover of cryptobiotic soil crusts (r = −0.47, P < 0.001), and positively correlated to native species richness (r = 0.22, P < 0.03), native species cover (r = 0.23, P < 0.05), and total nitrogen in the soil (r = 0.40, P < 0.001). Exotic species cover was strongly positively correlated to exotic species richness (r = 0.68, P < 0.001). Only 6 of 97 plots did not contain at least one exotic species. Exotic species richness was particularly high in
locally rare, mesic vegetation types and nitrogen rich soils. Dry, upland plots (n = 51) had less than half of the exotic species richness and cover compared to plots (n = 45) in washes and lowland depressions that collect water intermittently. Plots dominated by trees had significantly greater
native and exotic species richness compared to plots dominated by shrubs. For the 97 plots combined, 33% of the variance in
exotic species richness could be explained by a positive relationship with total plant cover, and negative relationships with
the cover of cryptobiotic crusts and bare ground. There are several reasons for concern: (1) Exotic plant species are invading
hot spots of native plant diversity and rare/unique habitats. (2) The foliar cover of exotic species was greatest in habitats
that had been invaded by several exotic species.(3) Continued disturbance of fragile cryptobiotic crusts by livestock, people,
and vehicles may facilitate the further invasion of exotic plant species.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Colorado Plateau cryptobiotic crusts exotic species richness invasive species native plant diversity vulnerable habitats |
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