A resilient system: North American mixed-grass prairie responds rapidly to livestock exclusion

Abstract

Grasslands are the most threatened terrestrial ecosystem in the world, and as their extent declines so does the abundance of species that depend on them. Periodic resting of rangelands could be used to manipulate plant cover and create wildlife habitat, but its effects may vary with prior grazing intensity. Using a large-scale manipulative grazing experiment conducted from 2006 to 2014 in Grasslands National Park, Canada, we evaluated how the effects of rest on vegetation and songbird abundance varied based on previous cattle stocking rates. Our results indicate that in northern mixed-grass prairies, grazing-induced changes were reversible, even at high stocking rates applied for up to four years. Both vegetation and songbirds were resilient to grazing, generally returning to levels observed prior to livestock reintroduction in three or fewer years following removal of livestock. Songbirds with flexible habitat requirements, such as Passerculus sandwichensis and Ammodramus savannarum, responded more rapidly to livestock exclusion. Recovery of both plant and songbird species occurred more rapidly in lowlands than uplands. The retrogressive nature of succession in North American mixed-grass prairies offers managers an opportunity to take chances when attempting to create wildlife habitat with livestock grazing, as risk of irreversible change is relatively low under moderate climate conditions.