Smothering invaders: the use of plastic tarps for controlling Urochloa eminii in South Brazilian grasslands

Abstract

In South Brazilian grasslands, invasion by African C4 grasses, such as Urochloa eminii (Mez) Davidse (formerly U. decumbens), poses a significant threat to biodiversity. We conducted an experiment to evaluate the effects of plastic tarps and herbicide application on U. eminii cover in a heavily invaded protected area. We established eight experimental blocks, each subdivided into six plots of 5 m × 3 m with the experimental treatments. The treatments were: black tarp for 30 days, black tarp for 60 days, transparent tarp for 30 days, transparent tarp for 60 days, herbicide application, and mowing only (control). Vegetation regeneration was analyzed in three plots (1 m2) within each treatment plot before and 90 days after the experiment was initiated. We used linear mixed models to assess treatment effects on U. eminii cover, native richness, and native cover, considering the difference between both samplings. All treatments were effective in the initial control of the invader. Black tarp proved to be more efficient compared to the transparent tarp. After tarp coverage, native species that first regrew were mainly plants with xylopodium/woody roots. Herbicide plots showed an increase in native species' cover and richness, but this positive initial effect on native species establishment might be counteracted by a fast return of the invader. The use of tarps may be an efficient alternative and a complementary technique to the use of herbicides and other control methods. Our study provides directions for the efficient use of tarps for U. eminii control and points toward areas for further research.