Using Adaptive Management to Restore Grasslands Invaded by Tall Fescue (Schedonorus arundinaceus)

Abstract

Invasive grasses reduce habitat quality for multiple taxa and can negatively impact forage quality for livestock. Large-scale experimental studies are needed to inform more effective grassland restoration that is grounded in practice. To this end, we studied the control of a common but highly invasive cool-season grass using a landscape-scale experiment, employing an adaptive management framework. The study design included three patches (average 8.7 ha) at each of seven sites. Treatments included 1) herbicide (glyphosate), 2) herbicide and native seeding, and 3) control. Four sites were grazed by domestic cattle using adaptive stocking. We sampled vegetation composition and structure during one pretreatment year (2014) and four post-treatment years (2015–2018). Our primary objective was to evaluate how these one-time treatments affected the cover of tall fescue (Schedonorus arundinaceus) and native grasses and forbs. Tall fescue cover was reduced after a one-time glyphosate application, and this reduction was maintained over 4 years on grazed and ungrazed sites. We observed increases of warm-season grasses after herbicide and seeding, with the strongest restoration observed on ungrazed sites. Native grasses did not differ strongly between treatments on grazed sites, where there was a resurgence of nonfescue exotic grasses. Percent cover of native forbs was near zero before seeding but ranged from low to moderate levels afterward. Our results indicate a one-time application of herbicide can be used to reduce but not eradicate the invasive grass tall fescue, although other exotic grasses may replace tall fescue, especially on grazed sites. For plant community restoration to be successful, sites should be rested from grazing to give native seedings time to establish. Although eradication of invasive grasses is often infeasible in productive landscapes, restoring at least some native vegetation has the potential to protect ecosystem services provided by grasslands.