Effect of fire, herbicide, and mowing on smooth brome and re-establishment of a sand prairie

Background/Question/Methods

Control of invasive species is essential for the success of any restoration project.  Smooth brome (Bromus inermis) is a perennial, cool-season grass native to Eurasia that is frequently encountered in prairie restoration sites in North America.  A lack of published information comparing the success of control methods leaves land managers to rely on word of mouth and anecdotal evidence for decision-making.  We are studying the efficacy of fire, herbicide (2% glyphosate), mowing, and fire + herbicide for controlling smooth brome and re-establishing sand prairie in southwestern Wisconsin.  Seven treatments (two frequencies each of fire, herbicide and mowing, and a single fire + herbicide), a seed only control and full control were replicated 8 times in a randomized block design (2m x 2m plots). We applied treatments in May and June 2007 and in early July seeded all but full control plots with a 21-species seed mix appropriate to the site.  We measured foliar cover of smooth brome and seeded species, litter depth, light, and soil moisture in September to assess the initial treatment effects.  

Results/Conclusions Smooth brome cover was reduced significantly by all treatments, more so by herbicide and fire + herbicide.  Litter depth was significantly lower in fire and fire + herbicide plots, while light availability at ground level was significantly higher in herbicide and fire + herbicide.  Treatments had no effect on soil moisture at either 10 or 30 cm depths. Germination of seeded species occurred in 24 of the 56 treated plots, but cover of seeded species was significantly greater than controls only in the fire + herbicide treatment. After this first set of treatments, herbicide and fire + herbicide appear to be the most successful methods for controlling smooth brome. The fire + herbicide treatment may be the most beneficial for initial prairie development, perhaps as the result of both increased light availability and decreased litter depth. We will continue to monitor the plots for the next two field seasons to assess long-term differences in the effect of restoration methods on smooth brome cover and native plant establishment.