Evaluating Restoration Methods across a Range of Plant Communities Dominated by Invasive Annual Grasses to Native Perennial Grasses

Abstract

Prairies are imperiled habitats, with remnants being generally small and often existing in isolation. Invasive plants have the potential to invade not just the edge of small remnants but also the interior because smaller remnants experience greater edge effects than do large, contiguous prairies. Additionally, invasive plants limit recruitment of native plants, which can arrest secondary succession. We proposed to assess techniques for restoration that included removing annual grasses and supplementing native species recruitment with seeding of native grass and forb species. We also assessed the effect of specific factors affecting recruitment: soil moisture and seed predation. Treatments included broadcast, spot, or no application of the herbicides imazapic and glyphosate and with or without seeding plus mulch. With treatments nested within each of three plant communities, ranging from annual- to perennial-dominated communities, in four blocks per community, plant characteristics (percentage of cover and plant density), soil moisture availability, and seed-predation losses were measured along a plant community gradient within one season at two locations. A combination of broadcast herbicide application and seeding with mulching was found to be more effective in reducing annual grasses and enhancing the establishment of native grass species in predominately annual and mixed communities (annuals and perennials). Spot herbicide application was effective in predominately perennial communities, whereas only seeding native species did not improve recruitment. Although seed predation reduced seedling recruitment, mulch provided seed protection and enhanced soil moisture retention. Plant community response to imposed treatments differed among communities, suggesting that a decision support tool would facilitate management decisions tailored for each plant community. The decision tool would be useful to ensure that appropriate treatments are applied and that specific factors affecting recruitment, such as seed predation and soil moisture, are addressed.

Efficacy of Exotic Control Strategies for Restoring Coastal Prairie Grasses

“…Our results are consistent with many previous studies showing that both herbicides and mulch are effective in reducing exotic grass competition and favoring native grasses (e.g., Cox and Allen 2008;Huddleston and Young 2005;Irvine et al 2013;Kettenring and Adams 2011;Nyamai et al 2011). Exotic control treatments had much weaker and less consistent effects on cover of exotic forbs, which likely reflects the fact that cover of exotics forbs, many of which are low-stature and/or have basal rosettes, is strongly influenced by competition with taller-stature grasses, both native and exotic (Cox and Allen 2011;Hayes and Holl 2011).…”

“…Mulch also increases soil moisture, which can enhance seed germination and seedling survival in arid systems (Biederman and Whisenant 2009;Nyamai et al 2011). The vast majority of wood mulch breaks down within 2 yr in our study system, so in turn these effects are expected to decrease.…”

Comparison of Methods for Restoring Meadows Invaded by Solidago Species

“…Using a herbicide can quickly eradicate or limit invasive species [29][30]47]. Our experiments reveal that Solidago spp.…”

“…Thus, many semi-natural meadow restoration projects spread fresh hay, which contains the seeds of target species [32,[45][46]. Our experimental results show that fresh hay was an efficient source of target species propagules, even in grasslands seriously affected by invasive plant species, but the efficiency of target species emergence depends on the method used to remove the alien species.Using a herbicide can quickly eradicate or limit invasive species [29][30]47]. Our experiments reveal that Solidago spp.…”

“…cover decreased rapidly after applying a glyphosate-based herbicide, and the dominant species were F. pratensis, A. pratensis, and P. trivialis. These perennial grass species are highly competitive and can effectively reduce the occurrence of non-target species [33,47]. Other species, such as L. pratensis and F. rubra, along with dominant grasses resulted in good tolerance of mowing and a high forage value for the sward after applying glyphosate.…”