Controlling the invader Urochloa decumbens: subsidies for ecological restoration in subtropical Campos grassland

Pedro Augusto Thomas, Jéssica Schüler, Lidiane da Rosa Boavista, Fábio Piccin Torchelsen, Gerhard Ernst Overbeck & Sandra Cristina Müller

Experimental plot after the application of herbicide and topsoil removal. In the background of the photo, behind the plot, and in the foreground experimental plots, we can see Urochloa decumbens. Porto Alegre, Brazil. Photo credit: Pedro Augusto Thomas.

Our research investigated the control of a common invasive grass (Urochloa decumbens) in the subtropical grasslands of southern Brazil, known as Campos Sulinos. Although these grasslands are one of the most biodiverse grassland ecosystems in the world, there is a lack of experience and knowledge about how to control this invasive grass. In an area widely dominated by U. decumbens, we tested combinations of two control techniques (herbicide application and topsoil removal), together with two techniques to reintroduce native species (hay transfer and sowing seeds). We hypothesized that establishing more native species could help us to control the invasive grass. We initiated the experiment in summer 2016 and analysed the response of the vegetation in summer 2017. We found that both herbicide application and topsoil removal were effective in reducing the invasive grass cover, with herbicide application being more effective. Neither hay transfer nor sowing were effective in establishing more native species in the experimental area. Plots with less U. decumbens (those that received herbicide application or topsoil removal) had higher native species richness. However, both these control techniques are difficult to apply over an area without affecting native species. Moreover, other studies show negative impacts of herbicide application, so more studies are necessary before this technique could be widely recommended. Despite having reduced the abundance of the invasive grass, the vegetation was still very different than in conserved grasslands and more experiments should take place, with an emphasis on increasing the diversity and abundance of native species.

A schematic design of experimental blocks with the combination of different techniques. Figure from the original paper.

This is a plain language summary for the paper of Thomas et al. published in the Applied Vegetation Science.