Grazing, a defining use of rangelands, can have immediate and legacy impacts in ecosystems with short evolutionary histories of grazing and where climatic conditions are marginal and variable. In arid rangelands of the Colorado Plateau, domesticated ungulates were introduced in the 1800s at high densities and grazing has been maintained in the region at variable stocking rates for approximately the past 150 yr. Historic grazing practices, combined with a marginal climate, may have caused an irreversible shift in the vegetation community leading to limited recovery with cessation of grazing. Using three exclosures ranging from 12 to 50 yr of age, we evaluated vegetation composition, diversity, and cover inside the exclosures and compared them with directly adjacent, actively grazed areas outside of the exclosures in the fall and spring of 2018 and 2019. We then asked 1) How do exclosures and their adjacent unexclosed sites differ in vegetation diversity, composition, and cover? and 2) Are there significant differences in cover of key forage species in exclosed versus unexclosed areas? Overall, there were significant differences in vegetation communities inside and outside of exclosures in both seasons. Composition, alpha, and beta diversity differed between grazed and exclosed sites, with higher alpha and beta diversity in the 50-yr exclosure in the fall. Composition was significantly different between exclosures and unexclosed sites at all sites and in all seasons. Cover of several important forage grasses (Achnatherum hymenoides, Hilaria jamesii, Elymus elymoides) was higher in exclosed areas, while cover of Scleropogon brevifolius and Bouteloua gracilis was higher in unexclosed areas. Taken together, these results indicate limited recovery of vegetation in the absence of grazing, with exclosures exhibiting higher plant diversity, as well as cover of some desirable forage species, suggesting this area has not undergone irreversible state change but recovery may require > 50 yr of grazing cessation.

放牧是牧场的一种明确用途，可以对放牧进化历史较短且气候条件边际和多变的生态系统产生直接和遗留影响。在科罗拉多高原的干旱牧场，驯化的有蹄类动物在 1800 年代以高密度引入，并且在过去大约 150 年里，该地区一直以不同的放牧率维持放牧。历史上的放牧做法，加上边缘气候，可能导致植被群落发生不可逆转的转变，导致随着停止放牧而有限的恢复。使用年龄从 12 到 50 岁不等的三个围场，我们评估了围场内的植被组成、多样性和覆盖，并将它们与直接相邻的、2018 年和 2019 年秋季和春季在围场之外的活跃放牧区。然后我们问 1) 围场及其相邻的未围场在植被多样性、组成和覆盖方面有何不同？2) 开放和非开放区域的主要牧草物种覆盖率是否存在显着差异？总体而言，两个季节围地内外的植被群落存在显着差异。放牧和封闭场地的组成、α 和β 多样性不同，秋季50 年封闭场地的α 和β 多样性更高。在所有地点和所有季节，外地和未外地之间的组成有显着差异。几种重要牧草的覆盖 然后我们问 1) 封闭区及其相邻的未封闭区在植被多样性、组成和覆盖方面有何不同？2) 开放和非开放区域的主要牧草物种覆盖率是否存在显着差异？总体而言，两个季节围地内外的植被群落存在显着差异。放牧和封闭场地的组成、α 和β 多样性不同，秋季50 年封闭场地的α 和β 多样性更高。在所有地点和所有季节，外地和未外地之间的组成有显着差异。几种重要牧草的覆盖 然后我们问 1) 封闭区及其相邻的未封闭区在植被多样性、组成和覆盖方面有何不同？2) 开放和非开放区域的主要牧草物种覆盖率是否存在显着差异？总体而言，两个季节围地内外的植被群落存在显着差异。放牧和封闭场地的组成、α 和β 多样性不同，秋季50 年封闭场地的α 和β 多样性更高。在所有地点和所有季节，外地和未外地之间的组成有显着差异。几种重要牧草的覆盖 两个季节围地内外的植被群落存在显着差异。放牧和封闭场地的组成、α 和β 多样性不同，秋季50 年封闭场地的α 和β 多样性更高。在所有地点和所有季节，外地和未外地之间的组成有显着差异。几种重要牧草的覆盖 两个季节围地内外的植被群落存在显着差异。放牧和封闭场地的组成、α 和β 多样性不同，秋季50 年封闭场地的α 和β 多样性更高。在所有地点和所有季节，外地和未外地之间的组成有显着差异。几种重要牧草的覆盖（Achnatherum hymenoides、Hilaria jamesii、Elymus elymoides）在未开放地区的覆盖率较高，而Scleropogon brevifolius和Bouteloua gracilis在未开放地区的覆盖率较高。综上所述，这些结果表明在没有放牧的情况下植被恢复有限，围场表现出更高的植物多样性，以及一些理想的草料物种的覆盖，表明该地区没有发生不可逆转的状态变化，但恢复可能需要 > 50 年的放牧停止。