Distinctive seed dispersal and seed bank patterns of invasive African grasses favour their invasion in a neotropical savanna

Xavier, Rafael de Oliveira; Christianini, Alexander V.; Pegler, Gabriela; Leite, Marcelo Boccia; Matos, Dalva Maria da Silva

doi:10.1007/s00442-021-04904-z

Cited by 11 publications

(13 citation statements)

References 69 publications

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“…This characteristic and, in fact, overall seed biology was poorly understood for many EPGs but suggests that this will be a critical research area for predicting risk of EPGs in any region. Evidence of the importance of seed banks for invasion has been noted in Brazil where difference in seed production and seed bank persistence favoured invasive African grasses over natives (Dairel & Fidelis, 2020; Xavier et al, 2021). Similar patterns of exotic seed pressure overwhelming native species appear to be driving successful invasion of EPGs in our study.…”

Section: Discussionmentioning

confidence: 99%

Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Rayment

French

Bedward

2022

Diversity and Distributions

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Aim Exotic perennial grasses (EPGs) are significant invaders of native grassy communities. We sought to determine how the profile of invading perennial grasses varies among different climatic regions and different grassy communities, to understand at which scale management is best undertaken. We investigated whether invader occurrence was related to specific plant traits. Location New South Wales, Australia. Method Field surveys of EPGs at 139 sites from nine grassy communities across four regions were assessed for variation in invasion profiles amongst regions and communities. We used a ranking of invasion risk based on plant characteristics to identify grasses likely to be more invasive and tested whether this ranking predicted the level of invasion in the survey. Results Using multivariate analysis, we found that all communities were significantly invaded. These assemblages were distinct regionally, and for most plant communities. Five widespread invaders were established in all regions and communities. Invasion by pasture grasses (termed trade‐off species) was the most significant threat, coupled with capacity to develop long‐term seed banks and use allelopathy. Species with higher risk rankings were recorded in more sites, although a few grasses had much greater occurrences than their ranking predicted. Conclusions Grassy communities across all regions were invaded by a suite of EPGs, some that have not been considered as problematic previously. Higher levels of invasion were associated with higher ranked species based on plant traits, indicating that our risk assessment is valuable as a management prioritization tool. Findings support community level management, although some species are important widespread invaders and could be managed at larger scales. Differences in species assemblages compared to nearby agricultural areas confirm different invasion pathways, with significant invasion from pasture grasses. Aided by the risk assessment tool, we propose that EPG management in native communities considers the climatic, community (including surrounding) and species level for prioritization.

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Section: Discussionmentioning

confidence: 99%

Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Rayment

French

Bedward

2022

Diversity and Distributions

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“…However, abundance and density present positive relationships with riparian forest width, and the larger the riparian forest is, the greater is the abundance and density of trees. This may be related to subtle changes on the larger riparian forests, such as small patches of better soil and microclimate conditions, due to the higher accumulation of litter above soil that acts on the nutrient cycling increasing the soil fertility, and to more shadow micro-sites, providing more environmental heterogeneity and better conditions to the plant germination and establishment (Boddey et al, 2004;Cole, Holl and Zahawi, 2010;Guareschi et al, 2014;Burdon et al, 2020;Gutiérrez-Chacón, Valderrama-a and Klein, 2020;Xavier et al, 2021). Also, larger riparian forests can suffer less edge effects over vegetation on the riparian zone interior (Griscom, Griscom and Ashton, 2009;Feld et al, 2018;Burdon et al, 2020;Xavier et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…In Brazil, the alien species Urochloa decumbens (Stapf) R.D. Webster, brachiaria-grass (former Brachiaria decumbens), is known as an aggressive species for the high competitive ability for water, light and nutrients in detriment to forest native species, as well for the great longevity of the seeds on the soil seed bank, an efficient energetic metabolism (C4) and seed dispersal, with high production of biomass, being also associated with the increase of risk of fire in the dry season (Marod et al, 2002;Marod et al, 2004;Ribeiro et al, 2006;Scervino and Torezan, 2015;Ferreira et al, 2016;Cury et al, 2020;Xavier, et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Tree diversity in riparian forests immersed in a pasture with Urochloa decumbens (Stapf) R.D. Webster (Poaceae) grass under domain of the Atlantic Forest, Brazil

Scervino¹,

Canto²,

Queiroga³

2023

Braz. J. Anim. Environ. Res.

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The riparian vegetation along water courses and the health of the river’s basin, regarding the aquatic and terrestrial ecosystems associated with them, are widely discussed in literature. However, the maintenance of the services and the conservation role that riparian forests provide to flora and fauna may be affected by the regional matrix that surrounds the water course and by the length and composition of the riparian vegetation associated with them. This study aimed to evaluate the relationships among the grass cover and arboreal species diversity in three watercourses surrounded by a pasture dominated with the alien grass Uroclhoa decumbens (Stapf) R.D. Webster (former Brachiaria decumbens). Two hypotheses were tested: (i) watercourses with larger riparian forest width present higher richness and abundance of native and zoochoric tree species and those associated to late succession stages, and (ii) watercourses with larger riparian forest width present a lower grass cover on their interior. The study was conducted under domain of Semideciduous Seasonal Forest, belonging to the Atlantic Forest biome, municipality of Londrina, Paraná State, south Brazil. The regional climate is Köppen’s Cfa humid subtropical. The soil is classified as a mosaic of eutroferric red nitosols and lithosols. The studied sites mostly comprise pasture with U. decumbens alien grass and small patches of woody vegetation amidst an open pasture dominated by species attributed to the first’s stages of secondary succession. The studied site is immersed in Cambé’s River watershed and contain three watercourses, Cristal River, tributary to São Lourenço River, that, in turn, is tributary to Cambé River. All watercourses are classified as small rivers (Brazilian Forestry Code, federal law: n. 12.651/2012), with length inferior to 10 m between both riversides. The riparian vegetation shares similar characteristics and structure, encompassing woody vegetation with pioneer trees species and high canopy openness. All riparian forests are immersed in pastures with U. decumbens grass. Transects of 200 meters long, measuring one meter wide from the line on both sides of the transect, and one square plot (25 m2) were allocated on the interior of each riparian forest. Transects were evaluated as arboreal species richness and the length of the riparian forest strip. In each plot, the arboreal vegetation was inventoried as species richness, abundance and density, and the U. decumbens cover was measured. The riparian forest width was arranged in two classes, forests with width ≤ 5 m or ≥ 10 m. The studied forests were compared as richness, abundance, density, and grass cover. The correlations among the riparian vegetation with the forest width and grass coverage (%) were evaluated. Species richness, abundance and density did not differ among the watercourses. However, species abundance and density presented positive correlations with the riparian forest width, indicating that the larger is the riparian vegetation, the higher is the species density. Grass cover presents a strong negative correlation with the riparian forest width, indicating that narrow strips of woody vegetation present higher grass cover. A high positive correlation was observed with riparian strip width and native trees, suggesting that native woody species establishment is limited by the riparian strip width and that those rustic trees species are more capable to colonize these environments. Also, the correlation found with species that present abiotic syndromes and pioneer species indicates that trees that can colonize open areas are more suitable to establish on narrow strips of vegetation amidst a pasture. The relationships observed with zoochoric trees suggests that the fauna that visits these forests are tolerant to open areas and visit these areas independently of their vegetation width. The larger riparian forests present lower grass cover and these can be related to shadow micro-sites that reduce the luminosity which can affect the permanence potential of the dominance of U. decumbens. In this way, the data suggests that few plants can establish in these pasture landscape, and those more rustic trees which are able to establish under open areas, high grass cover and canopy openness, and that re-sprout after a fire, became more dominant. For these watercourses, with narrow riparian vegetation strips surrounded by an U. decumbens pasture, the high grass cover can restrict and plant diversity, acting on the course and velocity of secondary succession in these areas.

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“…The increasing incidence of invasive species in savannahs worldwide (Davis et al, 2005; Hoffmann & Haridasan, 2008; Gorgone‐Barbosa et al, 2015; Oduor, 2021; Xavier et al, 2021) may also impact the establishment of woody plants in these habitats. However, the direction of this impact is difficult to predict.…”

Section: Introductionmentioning

confidence: 99%

An invasive grass and litter impact tree encroachment into a native grassland

Dettlaff

Erbilgin

Cahill

2021

Applied Vegetation Science

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Questions Woody plant encroachment and invasive plants are two critical factors that negatively impact grass‐dominated ecosystems. While studies have extensively investigated these factors individually, research on how invasive species impact the susceptibility of grasslands to encroachment is less common. Using the aspen parkland, an endangered savannah‐type ecosystem, we asked how the presence of a widespread invasive grass in North America, smooth brome (Bromus inermis), impacted the growth and survival of one‐year old trembling aspen (Populus tremuloides) seedlings. We also asked if plant litter was a potential mechanism of inhibition (as has been proposed for brome litter) or coexistence (as has been hypothesized for aspen litter) in this system. Location Alberta, Canada. Methods We used a manipulative experimental approach to determine if the survival and subsequent growth of planted aspen seedlings was impacted by the presence of smooth brome and manipulation of litter amount and type. Results We found that the presence of smooth brome reduced aspen survival by 57% compared to uninvaded habitats, likely mediated by reduced soil moisture, while litter manipulation had no effect on survival. For surviving seedlings, local context had complex impacts on growth; the addition of aspen litter to brome‐invaded communities increased seedling growth while aspen litter additions to native communities resulted in decreased growth. Conclusion These results suggest that invasion by smooth brome will alter the dynamics of aspen establishment in this system, potentially leading to significant changes to this already endangered landscape. Though smooth brome may serve as a barrier to aspen establishment, accumulation of aspen litter from nearby stands to brome patches could lead to faster growth of seedlings in invaded areas at the edge of existing aspen stands. Our results also suggest more generally that the impact of invasive plants on the establishment of native woody plants can be dependent on litter inputs.

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Distinctive seed dispersal and seed bank patterns of invasive African grasses favour their invasion in a neotropical savanna

Cited by 11 publications

References 69 publications

Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Tree diversity in riparian forests immersed in a pasture with Urochloa decumbens (Stapf) R.D. Webster (Poaceae) grass under domain of the Atlantic Forest, Brazil

An invasive grass and litter impact tree encroachment into a native grassland

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