Traits of the invasive Centaurea maculosa and two native grasses: effect of N supply |
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Authors: | P S Blicker B E Olson R Engel |
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Institution: | (1) Department of Land Resources and Environmental Sciences, Montana State University-Bozeman, Bozeman, MT 59717, USA;(2) Department of Animal and Range Sciences, Montana State University-Bozeman, Bozeman, MT 59717, USA |
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Abstract: | The Eurasian forb Centaurea maculosa (Lam.; spotted knapweed) has invaded millions of hectares of semi-arid grasslands in western North America. It readily colonizes disturbed areas, but also invades pristine grasslands. C. maculosa's success could be attributed to greater use, or more efficient use, of available soil nitrogen (N). Soil N often limits growth on semi-arid grasslands. Greater or more efficient use of soil N by C. maculosa, if this occurred, may inhibit establishment, survival, or reproduction of native grasses. In a glasshouse, C. maculosa and two native grasses, Pseudoroegneria spicata Scribn. and Smith] A. Love and Pascopyrum smithii Rybd.] A. Love, were grown in mixed- and monoculture for 8 weeks to determine growth response to two soil N supplies, which mimicked low and high N mineralization rates in semi-arid grasslands. At the end of the 8 weeks, plants were exposed to 15N-labeled nitrate for 24 h, and harvested to compare uptake of NO3
–. C. maculosa's growth response to N indicated that it was more competitive for N than the tussock grass P. spicata, but less competitive than the rhizomatous grass P. smithii. C. maculosa used nitrogen less efficiently than both of these native grasses. C. maculosa roots took up more 15N per unit root mass than the grasses, but acquired less N than P. smithii because P. smithii had greater root mass than C. maculosa. Total biomass and 15N uptake of C. maculosa varied depending on which species it was growing with. C. maculosa's success cannot be explained wholly by greater or more efficient use of soil N than that of the native grasses with which it competes. |
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Keywords: | biomass invasive isotope roots semi-arid shoots uptake |
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