Otfinowski, R., Kenkel, N. C. and Catling, P. M. 2007. The biology of Canadian weeds. 134. Bromus inermis Leyss. Can. J. Plant Sci. 87: [183][184][185][186][187][188][189][190][191][192][193][194][195][196][197][198]. Smooth brome (Bromus inermis Leyss.), a native of central Eurasia, was introduced to Canada as a forage and hay crop around 1888. Early reports of plants escaped from cultivation appear in 1903, and based on the number of collections prior to 1920, smooth brome spread most rapidly in western Canada. It is common along roadsides, forest margins, clearings, shorelines and disturbed areas, but its most detrimental impact is on the diversity of prairies and native grasslands. For example, in Riding Mountain National Park, MB, plant diversity of fescue prairies recently invaded by smooth brome decreased by 70%. Vegetative proliferation through underground rhizomes is key to the invasiveness of smooth brome, but long-range dispersal of seeds is facilitated by animals, wind and the transport of hay. Smooth brome is effectively controlled using selective applications of glyphosate and well-timed clipping. However, restoration of infested areas depends on the composition of native seed banks. Smooth brome remains valuable as a forage and cover crop in every province and territory in Canada. [183][184][185][186][187][188][189][190][191][192][193][194][195][196][197][198]. Le brome inerme (Bromus inermis Leyss.), plante indigène du centre de l'Eurasie, a été introduit au Canada pour la production fourragère vers 1888. Les premiers rapports mentionnant des plants retournés à l'état sauvage datent de 1903. D'après le nombre de prélèvements effectués avant 1920, on constate cependant que l'espèce s'est répan-due plus rapidement dans l'ouest du pays. Le brome inerme colonise souvent le bas-côté des routes, la lisière des bois, les clairières, les rivages et les terres perturbées, mais l'espèce nuit le plus à la diversité de la flore des prairies et des pâturages naturels. Dans le parc national Riding Mountain, au Manitoba, on a noté une diminution de la diversité des plantes de 70 % dans les prairies à fétuques récemment envahies par le brome inerme. L'efficacité du brome inerme vient essentiellement de sa reproduction végé-tative par rhizomes, mais les animaux, le vent et le transport du foin favorisent la dispersion des graines sur de grandes distances. L'application sélective de glyphosate et une coupe opportune permettent une lutte efficace contre cette adventice. Toutefois, la restauration des lieux infestés dépend de la composition des réserves de semences indigènes. Le brome inerme garde son utilité comme culture fourragère et culture abri dans toutes les provinces et tous les territoires du Canada. Mots clés: Bromus inermis Description and Account of Variation(a) Description. Rhizomatous perennial, 2-15 dm tall, the culms topped with open panicles 5-20 cm long with ascending or spreading branches. Rhizomes up to 1.5 m long without branching or producing stems, 2-5 mm wide, with pale scales. Culms smooth...
We evaluate the predictive power and generality of Shipley's maximum entropy (maxent) model of community assembly in the context of 96 quadrats over a 120-km2 area having a large (79) species pool and strong gradients. Quadrats were sampled in the herbaceous understory of ponderosa pine forests in the Coconino National Forest, Arizona, U.S.A. The maxent model accurately predicted species relative abundances when observed community-weighted mean trait values were used as model constraints. Although only 53% of the variation in observed relative abundances was associated with a combination of 12 environmental variables, the maxent model based only on the environmental variables provided highly significant predictive ability, accounting for 72% of the variation that was possible given these environmental variables. This predictive ability largely surpassed that of nonmetric multidimensional scaling (NMDS) or detrended correspondence analysis (DCA) ordinations. Using cross-validation with 1000 independent runs, the median correlation between observed and predicted relative abundances was 0.560 (the 2.5% and 97.5% quantiles were 0.045 and 0.825). The qualitative predictions of the model were also noteworthy: dominant species were correctly identified in 53% of the quadrats, 83% of rare species were correctly predicted to have a relative abundance of < 0.05, and the median predicted relative abundance of species actually absent from a quadrat was 5 x 10(-5).
Predicting exotic invaders and reducing their impacts on the biodiversity and function of native ecosystems require understanding of the mechanisms that facilitate their success during key stages of invasion. We determined whether clonal growth, characteristic of the majority of successful invaders of natural areas, facilitates the proliferation of Bromus inermis (smooth brome), an exotic grass invading prairie ecosystems across the Great Plains. By manipulating the below-ground connections of proliferating rhizomes as well as the levels of soil nitrogen along the margins of clones invading northern fescue prairies in Manitoba, Canada, we hypothesized that physiological integration would most benefit ramets invading low resource environments. Severing clonal connections reduced the mass of smooth brome shoots invading native prairies and was exacerbated by the immobilization of soil nutrients with glucose. Clonal connections were equally important in the maintenance of smooth brome density and the horizontal proliferation of ramets. Our results demonstrate the role of physiological integration in the proliferation of a clonal exotic invader and may help explain the success of clonal invaders in other regions. Although integration among invading ramets suggests several possibilities for successful management, future research must continue to elucidate differences in the invasiveness of native versus exotic species as well as the persistence of clonal connections among exotic invaders.
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