Variation in the effectiveness of nonnative plant removal along elevation gradients in Switzerland

Abstract Limiting the spread and impact of nonnative species in mountain ecosystems is a key management objective. While current management strategies may be tailored to species traits and life histories, understanding how management effectiveness varies along elevation gradients could help optimize control measures and ultimately support native plant communities. We hypothesized that management efficiency would increase with elevation due to smaller population sizes and more limiting environmental conditions affecting population performance near range edges. To test our hypothesis, we conducted a removal experiment with two perennial ( Solidago canadensis and Lupinus polyphyllus ) and one annual ( Erigeron annuus ) invasive species in the eastern Swiss Alps. Control effectiveness (recovery of plant cover after 1 year) depended on plant life history, with a strong reduction in cover for the perennial species. However, elevation did not significantly affect short-term management outcomes, suggesting consistent efficiency of control measures across the gradient. A germination experiment using soil samples from field sites revealed higher seedling numbers for the annual species and a decline in emergence with elevation for both focal species analyzed, suggesting that seed bank size may influence management outcomes. Based on our findings, we recommend long-term strategies that include the sowing of native seed mixtures to support recovery. Additionally, lower germination at higher elevations suggests that removal success may eventually be greater at species’ upper range limits. Overall, our study shows that considering elevation-related variation can help refine nonnative plant management strategies in mountains.