Roads as Conduits for Exotic Plant Invasions in a Semiarid Landscape

摘要: Roads are believed to be a major contributing factor the ongoing spread of exotic plants. We ex- amined effect road improvement and environmental variables on native plant diversity in roadside verges adjacent semiarid grassland, shrubland, woodland communities southern Utah (U.S.A.). measured cover species both richness interior (50 m beyond edge cut) along 42 roads stratified by level ( paved, improved surface, graded, four-wheel- drive track ). In paved roads, Bromus tectorum was three times as great (27%) four-wheel-drive tracks 9%). The five common forb tended lower than more roads. were 50% greater, 30% lower, at sites those tracks. addition, relating dominant vegetation, disturbance, topography significantly correlated with cover. Improved can act conduits for inva- sion ecosystems converting natural habitats highly vulnerable invasion. However, variation soil moisture, nutrient levels, depth, may render differentially susceptible invasions originating from verges. Plant that physically invasible (e.g., characterized deep or fertile soils) disturbed ap- pear most vulnerable. Decision-makers considering whether build, improve, maintain should take into account potential