Experimental grazing and grass-specific herbicide application benefit rare FORB recruitment

Native ungulate grazers affect plant richness, with many studies examining grazer effects on community composition and structure. However, the effect of grazing on the demography of rare plant species is less well understood. Grazers are expected to benefit many plant species by suppressing the competitive dominant grasses and by scarifying and dispersing rare plant seeds. A goal in conservation biology is to quantify the most important threats to rare plant species and to determine how different types of management can improve their demographic outlook. Here, we provide results from two experimental studies that examine (1) the effect of ungulate grazer presence, and (2) the effect of a grass-specific herbicide treatment on the recruitment of a focal rare plant species. Our study demonstrates that both treatments effectively reduce the percent cover or height of the dominant grass species and increase the recruitment of the rare legume, Lespedeza leptostachya. If our results are generalizable to other grassland ecosystems and rare forb species, it suggests that reintroducing grazers may be critical to the management of rare plants in these ecosystems. However, in small remnant habitats where ungulate reintroductions are not possible, conservation efforts can more directly target the reduction of grass competitors using alternative methods.