Abstract
Abstract The impacts of alien plants on native richness are usually assessed at small spatial scales and in locations where the alien is at high abundance. But this raises two questions: to what extent do impacts occur where alien species are at low abundance, and do local impacts translate to effects at the landscape scale? In an analysis of 47 widespread alien plant species occurring across a 1,000 km 2 landscape, we examined the relationship between their local abundance and native plant species richness in 594 grassland plots. We first defined the critical abundance at which these focal alien species were associated with a decline in native α ‐richness (plot‐scale species numbers), and then assessed how this local decline was translated into declines in native species γ ‐richness (landscape‐scale species numbers). After controlling for sampling biases and environmental gradients that might lead to spurious relationships, we found that eight out of 47 focal alien species were associated with a significant decline in native α ‐richness as their local abundance increased. Most of these significant declines started at low to intermediate classes of abundance. For these eight species, declines in native γ ‐richness were, on average, an order of magnitude (32.0 vs. 2.2 species) greater than those found for native α ‐richness, mostly due to spatial homogenization of native communities. The magnitude of the decrease at the landscape scale was best explained by the number of plots where an alien species was found above its critical abundance. Synthesis. Even at low abundance, alien plants may impact native plant richness at both local and landscape scales. Local impacts may result in much greater declines in native richness at larger spatial scales. Quantifying impact at the landscape scale requires consideration of not only the prevalence of an alien plant, but also its critical abundance and its effect on native community homogenization. This suggests that management approaches targeting only those locations dominated by alien plants might not mitigate impacts effectively. Our integrated approach will improve the ranking of alien species risks at a spatial scale appropriate for prioritizing management and designing conservation policies.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 6
Claim · model-written summary
Eight of 47 alien plant species were associated with a significant decline in native plant richness as their local abundance increased.
Verbatim
e0“In an analysis of 47 widespread alien plant species occurring across a 1,000 km 2 landscape, we examined the relationship between their local abundance and native plant species richness in 594 grassland plots”
e1“eight out of 47 focal alien species were associated with a significant decline”
Claim · model-written summary
Most significant declines in native richness started at low to intermediate abundance classes.
Verbatim
e0“In an analysis of 47 widespread alien plant species occurring across a 1,000 km 2 landscape, we examined the relationship between their local abundance and native plant species richness in 594 grassland plots”
e2“Most of these significant declines started at low to intermediate classes of abundance”
Claim · model-written summary
Declines in native gamma richness were an order of magnitude greater than declines in native alpha richness, 32.0 vs 2.2 species.
Verbatim
e0“In an analysis of 47 widespread alien plant species occurring across a 1,000 km 2 landscape, we examined the relationship between their local abundance and native plant species richness in 594 grassland plots”
e3“declines in native γ ‐richness were, on average, an order of magnitude (32.0 vs. 2.2 species) greater”
Claim · model-written summary
The landscape-scale decline is mostly due to spatial homogenization of native communities.
Verbatim
e0“In an analysis of 47 widespread alien plant species occurring across a 1,000 km 2 landscape, we examined the relationship between their local abundance and native plant species richness in 594 grassland plots”
e3“declines in native γ ‐richness were, on average, an order of magnitude (32.0 vs. 2.2 species) greater”
e4“mostly due to spatial homogenization of native communities”
Claim · model-written summary
The magnitude of the landscape-scale decrease was best explained by the number of plots where an alien species was above its critical abundance.
- Taxon
- alien speciese5
- Treatment
- number of plots where an alien species was found above its critical abundancee5
- Outcome
- magnitude of the decrease at the landscape scalee5
Not reportedDirection
Verbatim
e5“The magnitude of the decrease at the landscape scale was best explained by the number of plots where an alien species was found above its critical abundance”
Claim · model-written summary
Management targeting only locations dominated by alien plants might not mitigate impacts effectively.
Verbatim
e6“management approaches targeting only those locations dominated by alien plants might not mitigate impacts effectively”