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    Description

    Plant species assemblages, communities or regional floras might be termed saturated when additional immigrant species are unsuccessful at establishing due to competitive exclusion or other inter-specific interactions, or when the immigration of species is off-set by extirpation of species. This is clearly not the case for state, regional or national floras in the USA where colonization (i.e. invasion by exotic species) exceeds extirpation by roughly a 24 to 1 margin. We report an alarming temporal trend in plant invasions in the Pacific Northwest over the past 100 years whereby counties highest in native species richness appear increasingly invaded over time. Despite the possibility of some increased awareness and reporting of native and exotic plant species in recent decades, historical records show a significant, consistent long-term increase in exotic species (number and frequency) at county, state and regional scales in the Pacific Northwest. Here, as in other regions of the country, colonization rates by exotic species are high and extirpation rates are negligible. The rates of species accumulation in space in multi-scale vegetation plots may provide some clues to the mechanisms of the invasion process from local to national scales.

    Publication Notes

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    Citation

    Stohlgren, Thomas J.; Barnett, David T.; Jarnevich, Catherine S.; Flather, Curtis; Kartesz, John. 2008. The myth of plant species saturation. Ecology Letters. 11: 313-326.

    Keywords

    biotic resistance, competitive exclusion, habitat heterogeneity, invasion, plant diversity, saturation, species richness

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https://www.fs.usda.gov/treesearch/pubs/30717