Alien plant species on roadsides of the northwestern Patagonian steppe (Argentina)

Abstract

The introduction of alien species represents one of the greatest threats to biodiversity worldwide. Highway construction increases the dispersal and invasion of exotic plant species. This study examined the assembly process of the plant communities to determine whether the roadsides of the Patagonian steppe represent a reservoir and dispersal source of invasive exotic species. We analyzed the composition of exotic and native species and functional groups present in the established vegetation and seed banks of roadsides and reference areas nearby. The type of dispersal of exotic and native species at the roadsides was also evaluated. Total cover and that of exotic and native species was lower at the roadsides than in the reference areas; however, at the roadsides the cover and seed abundance of exotic species was higher than that of native species. In the roadsides vegetation, native shrubs such as Acaena splendens predominated, along with exotic perennial herbs and grasses which were mainly represented by Rumex acetosella. In the seed bank the predominant species were exotic perennial herbs, also represented by R. acetosella, annual exotic species such as Epilobium brachycarpum and Verbascum thapsus, and annual native species such as Heliotropium paronychioides. No exotic shrubs were found either at the roadsides or in the reference areas. The species at the roadsides did not present a dominant type of dispersal. The abundance of exotic species at the roadsides, both in the aboveground vegetation and the seed bank, may be due to the stressful environment and the characteristics of the species themselves, such as the ability to form seed banks. This work revealed that the roadsides of the Patagonian steppe constitute reservoirs of invasive exotic species, highlighting the importance of identifying them and controlling their spread, with a view to generating ecosystem management programs.

Abiotic and biotic contexts shape the effect of disturbance on non‐native plant invasion

“…Our results suggest that the relative importance of the plant invasion–disturbance relationship in explaining invasion patterns decreases when the importance of abiotic factors, compared to that of biotic factors, increases. Consistently, it has been found that non‐native cover in the harsh conditions of the Patagonian steppe is higher in non‐disturbed than disturbed communities suggesting that roadside disturbance per seis not an important mechanism explaining plant invasion patterns in that region (Chichizola et al 2021) . Under stressful conditions, stress tolerant species, rather than ruderal species, should dominate the non‐native pool (Grime 1977, Pearson et al 2018).…”

“…Positive coefficients depict a positive effect on non-native species cover/richness, whereas negative coefficients depict a negative effect. disturbed communities suggesting that roadside disturbance per se is not an important mechanism explaining plant invasion patterns in that region (Chichizola et al 2021). Under stressful conditions, stress tolerant species, rather than ruderal species, should dominate the non-native pool (Grime 1977, Pearson et al 2018.…”

“…However, empirical evidence is mixed (Smith and Knapp 1999, Moles et al 2012) and some studies have even reported a negative relationship between disturbance and invasion (Smith and Knapp 1999, Chichizola et al 2021). Disturbance type and frequency, methodological approach, and time after disturbance may all influence non‐native species response to disturbance (Moles et al 2012, Jauni et al 2015, Chichizola et al 2021) and, hence, help explain contradictory results. Differences in the abiotic and biotic context in which disturbance occurs could also explain discrepancies among studies (Chiuffo et al 2022).…”

“…Accordingly, many studies have reported an increase in non‐native basal area (Bellingham et al 2005), biomass (Domènech and Vilà 2006), cover and density (Hierro et al 2006), establishment (Burke and Grime 1996), survival (Domènech and Vilà 2006, De Villalobos et al 2011) and richness (Deutschewitz et al 2003, Sharma and Raghubanshi 2009, Paiaro et al 2011) with disturbance. However, empirical evidence is mixed (Smith and Knapp 1999, Moles et al 2012) and some studies have even reported a negative relationship between disturbance and invasion (Smith and Knapp 1999, Chichizola et al 2021). Disturbance type and frequency, methodological approach, and time after disturbance may all influence non‐native species response to disturbance (Moles et al 2012, Jauni et al 2015, Chichizola et al 2021) and, hence, help explain contradictory results.…”

Municipal solid waste landfill: Evidence of the effect of applied landfill management on vegetation composition

“…The richest species turned out to be complex families ( Asteraceae ), grasses ( Poaceae ) and legumes ( Fabaceae ). Many species belonging to Asteraceae and Poaceae produce high numbers of seeds adapted to wind dispersal (Chichizola et al, 2021), which can easily reach the surroundings. According to Kornaś and Medwecka-Kornaś (2002), habitats subjected to strong anthropogenic stresses are dominated by non-native species (anthropophytes).…”