Controlling the invaderUrochloa decumbens: Subsidies for ecological restoration in subtropical Campos grassland

Abstract

Questions:Restoration of grassy biomes is currently of large importance, and controlling invasive grasses is often key to restoring these ecosystems in the tropics and subtropics. We combined different ecological restoration techniques to evaluate potential to control the invasive grass Urochloa decumbens and restore plant species composition. Specific questions were: (a) are herbicide application and topsoil removal efficient to control U. decumbens cover and allow native species establishment; and (b) are hay transfer and sowing native grass species efficient to reintroduce native species and increase their cover? Location: Campos grasslands, southern Brazil. Methods: We combined the follow restoration techniques: (a) herbicide application or topsoil removal to control the invasive species, and (b) hay transfer or sowing of native grasses to reintroduce native species. We assessed and compared native plant species richness, vegetation cover, native species cover, U. decumbens cover and other exotic species cover in 2016 and 2017.Results: Herbicide application reduced invasive species cover more than topsoil removal, even though both were effective. The decrease of U. decumbens cover led to an increase in native species cover and native species richness. Hay transfer and sowing native grasses did not produce satisfactory results for native species reintroduction. Native species richness and U. decumbens cover increased from 2016 to 2017. Conclusion:Herbicide application was a better option to control U. decumbens and to allow recovery of native species. However, use of herbicides in restoration is controversial, and more detailed studies on impacts are necessary. Environmental filters appear to be a major cause for failure of hay transfer and seeding species. Recovery of the native plant community is a great challenge in invaded subtropical grasslands, and additional management actions and time are necessary to increase the establishment of native species.

Weed management for landscape scale restoration of global temperate grasslands

“…Also, as a result of fragmentation, many sites are isolated from remnant grasslands, making seed transfer by migration unlikely. Where natural regeneration is unlikely, competition from desirable native species can be introduced using a variety of methods including direct seeding (Cole et al, 2005; Thomas et al, 2019), transfer of threshing material (Baasch et al, 2016) or hay (Sengel et al, 2016), direct drilling (Bakker et al, 2003) and plant plugs (Tikka et al, 2001). Hedberg and Kotowski (2010) reviewed the effectiveness of different revegetation options for fragmented grasslands and found that direct seeding (sowing and broadcasting) to be the most widely used and most effective for introducing species back to semi‐natural systems.…”

Brushwood and artificial perch did not facilitate forest regeneration in Urochloa spp. grassland

“…Our results indicate that in pastures characterized by strong inhibitory vegetation, greater efforts in cleaning activities and methods to help induce natural regeneration should be combined to overcome both competitive and dispersal barriers, without which native species will have little chance of surviving (Tomazi et al 2010; Reid and Holl 2013; Barbosa et al 2018;Thomas et al 2019). Initially, brushwood treatments with and without perch reduced the Urochloa biomass.…”

Restoration of abandoned subtropical highland grasslands in Brazil: mowing produces fast effects, but hay transfer does not

“…Unlike temperate grasslands, where hay transfer has shown good results (Kiehl & Wagner 2006;Klimkowska et al 2010;Knut et al 2010;Schmiede et al 2012), in our experiment we did not manage to reintroduce species by this technique. Hay transfer was also not efficient for restoration in another recent restoration experiment in Campos Sulinos region (Thomas 2019), in Cerrado savannas (Pilon et al 2018) and in Campos Rupestres grasslands (Stradic et al 2013). Related reasons are still not entirely clear and could include unfavorable site conditions, lack of viable seeds in the hay, or presence of dormancy in seeds (Stradic et al 2013).…”