Establishment of Native Species in Soils From Russian Knapweed (Acroptilon Repens) Invasions |
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| Affiliation: | 1. Graduate Research Assistant, Department of Renewable Resources, University of Wyoming, Laramie, WY 82071;2. Associate Professor, Department of Renewable Resources, University of Wyoming, Laramie, WY 82071;3. Professor, Department of Renewable Resources, University of Wyoming, Laramie, WY 82071;4. Director of Stewardship, The Nature Conservancy of Wyoming, Lander, WY 82520;1. University of Vienna, Core Facility Cell Imaging and Ultrastructure Research, Althanstraße 14, A-1090 Vienna, Austria;2. University of Exeter, College of Life and Environmental Sciences, Biosciences, Stocker Road, Exeter EX4 4QD, United Kingdom;3. Leibniz University Hannover, Institute of Radioecology and Radiation Protection, Herrenhäuser Straße 2, D30419 Hannover, Germany;4. University of Vienna, Department of Microbiology and Ecosystem Science, Althanstraße 14, A-1090 Vienna, Austria;5. Instituto Nacional de Pesquisas da Amazônia, Coordenação de Dinâmica Ambiental, Manaus, Brazil;6. Helmholtz-Zentrum Dresden-Rossendorf, Division of Biogeochemistry, Bautzner Landstraße 400, D-01328 Dresden, Germany |
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| Abstract: | Russian knapweed (Acroptilon repens [L.] DC.), an exotic perennial forb, has invaded many native ecosystems in western North America. Russian knapweed's success is attributed to allelopathy, extensive tap rooting, zinc accumulation in soils, and a lack of North American predators. Revegetation following chemical control slows exotic reestablishment, but the impacts of Russian knapweed-invaded soils on the establishment of native forbs and shrubs have not been determined. In a greenhouse experiment, we monitored the establishment of two native forbs, Indian blanketflower (Gaillardia aristata Pursh) and purple prairie clover (Dalea purpurea Vent.) and two native shrubs, winterfat (Krascheninnikovia lanata [Pursh] A.D.J. Meeuse & Smit syn. Ceratoides lanata) and Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis [Hook.] Nutt.) in soils obtained from three Russian knapweed invasions and adjacent noninvaded areas. We analyzed soils collected near Greybull and Riverton, Wyoming, and Greeley, Colorado, for cation exchange capacity, organic matter, electroconductivity, pH, and total nitrogen, carbon, and plant-available potassium, zinc, manganese, copper, and phosphate. We documented seedling emergence of the four natives and Russian knapweed every two days for 14–17 weeks, harvested seedlings biweekly to assess their growth, and determined their zinc accumulation. All species established in invaded soil and seedlings were larger in invaded than in noninvaded soils. Invaded rangeland soils had greater organic matter (8.6% and 1.1% in invaded vs. 2.5% and 0.4% in noninvaded soils) and lower pH (7.4 in invaded versus 8.0 noninvaded soils). Zinc concentrations in invaded soils (from 0.15 to 6.56 mg · kg-1) were not high enough to limit plant growth. Reports that Russian knapweed is a hyper-accumulator of zinc are not supported by our seedling data, which suggests that previously invaded soils may not limit native seedlings. |
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