The growth form of dominant grasses regulates the invasibility of Uruguayan grasslands

Abstract

Abstract. In this paper we report the results of a small-scale experiment on patches of natural grasslands in Uruguay. We analyzed whether growth form of C 4 grasses affects invasion success. The experimental plots represented three patch-types arising from short-term grazing effects and were dominated by prostrate C 4 grasses, erect C 4 grasses and codominated by prostrate C 4 grasses and forbs. We seeded the plots with four exotic species: one perennial C 4 grass, one annual C 3 grass, one perennial forb and one annual legume. Contrary to many studies conducted at small spatial scales, our results suggest that in our system, the processes that control invasibility are not directly linked with resident species richness or biomass, but rather are driven by growth form. Emergence of invaders did not differ among patch-types, but seedlings survived less in plots dominated by erect grasses. We suggest that the erect growth form of C 4 grass species is more successful in preventing invasion by mediating seedling competition for light under the canopy for a longer period of time. Grazing management, through its ability to regulate canopy architecture, is a potentially important tool in controlling invasion.

Plant Colonization of Green Roofs Is Affected by Composition of Established Native Plant Communities

“…The direct effects of resident assemblage composition on colonization in our study suggest that species-specific interactions between resident and colonizing species affected colonization, as often has been observed in studies on natural systems (Bresciano et al, 2014). In the current study, the larger colonist dry mass in the HP treatment was associated with a resident assemblage dominated by several C 4 graminoids, compared with the RS treatment, where the assemblage was dominated by a C 3 tuft graminoid and forbs.…”

“…A key factor affecting colonization of green roofs may be the abundance and composition of resident plant species, just as priority effects affect colonization in natural systems (Chase, 2003;Fukami, 2015). For example, in grasslands, increased resident plant cover has been shown to decrease colonist species richness (Foster, 2001;Milbau et al, 2007), and specific growth forms, such as C 4 graminoids, may limit colonization more than other growth forms (Fargione et al, 2003;Bresciano et al, 2014). Moreover, the dominant growth form of resident species may lead to colonization by complementary growth forms, due to competition by similar growth forms (Macarthur and Levins, 1967;Fargione et al, 2003;Smith et al, 2004).…”

Spread of exotic grass in grazed native grass pastures and responses of insect communities

“…An important caveat to our results is that although the type of grazing management implemented in our study (continuous season-long) is common, other grazing regimes may not yield the same results that we observed, particularly if bermudagrass spread is driven by greater insolation from reductions in plant height and canopy coverage (Dong & de Kroon 1994;Bresciano et al 2014). For example, season-long grazing may increase and maintain openness at ground level whereas early-season grazing (for 30 days in May) can result in greater vegetation density later in the growing season (Harper et al 2015).…”

“…According to the enemy of my enemy hypothesis, grazing can benefit exotic species through apparent competition when an herbivore has a greater impact on native than exotic grasses (Colautti et al ). In our study, the erect growth form of bunchgrasses makes them more effective at competing for light than prostrate grasses (Chaneton et al ), and low light conditions can limit growth of bermudagrass (Dong & de Kroon ; Newman et al ; Bresciano et al ). This is supported by our finding little change in bermudagrass coverage among non‐grazed NWSG where VOR was greater than in grazed pastures.…”

Community Attributes Predict the Relationship between Habitat Invasibility and Land Use Types in an Agricultural and Forest Landscape

“…A species-rich community use environmental resources more fully and less resource will be left for the alien plants [17]. According to the sampling effect, a species-diverse community is more likely to contain highly suppressive species to inhibit alien plant invasion by competing for resources [54,55] or by producing antagonistic substances [56]. Decreases in stem density and species diversity in the overstory may also increase plant invasion severity by reducing the effects of shading exclusion on invasive plants.…”