Native prairie grasslands are a fundamental part of Canada’s natural heritage, but these formerly extensive ecosystems have undergone declines due to grassland conversion and fragmentation. In addition, remaining native grasslands are threatened by invasive non-native plants, which can outcompete native flora and negatively impact ecological functioning. Although several studies have reported invasions in northern prairie grasslands, only some have investigated overall patterns across a large regional gradient, and few have tested their relationship with environmental predictors and anthropogenic disturbance. We surveyed 140 plots across a latitudinal gradient in prairie grasslands of Alberta and asked: (1) What are the most frequent and abundant non-native vascular plant species? (2) Are levels of invasions are linked to environmental factors or anthropogenic disturbance? (3) Do these relationships differ between mesic and semi-arid grasslands? Data were analyzed using generalized additive models and commonality coefficient analysis.
Results/Conclusions
Our results show that Kentucky bluegrass (Poa pratensis subsp. angustifolia), is the most frequent and abundant non-native plant in Alberta prairie grasslands. Across all plots, abundance and richness of non-native plants were positively linked to a shared effect by aridity, soil texture, and agricultural activity, with mesic loamy grasslands having the highest levels of invasion. In mesic grasslands, non-native plant abundance and richness was highest in areas with high agricultural activity and fine-textured soils. By contrast, topography explained most variation in the levels of invasion in the semi-arid prairie. A priority for future research is to identify the mechanisms underlying the differences in invasion across mesic and semi-arid prairie grasslands. To counteract invasions, practitioners need to diminish the propagule pressure by invasive agronomic grasses, protect and restore grassland remnants in the mesic region, and proactively control new invaders.
