Scientific interest in plant invasions in mountains is growing, together with the global exponential increase in these invasions. Current research mostly consists of observational studies, with only limited information from experiments, leaving important questions about the roles of and interaction between all possible drivers of mountain invasion unanswered. We integrate human-mediated (i.e. disturbance, nutrient addition and propagule pressure) and climatic factors into one multi-factorial cross-continental experiment to disentangle their roles in driving or limiting plant invasions. With this experiment along elevation gradients from lowlands to the alpine zone in two high-latitude regions in Sweden and Chile, we shed light on the possibilities for invaders at the invasion front in cold environments.
Results/Conclusions
We show how virtually all measures of invader success showed a quadratic correlation with elevation, with competition being the main limitation for invasions at low elevation and cold climate reducing invader success at high elevations. Disturbance turned out to be the main driver of invader success besides elevation, with high nutrient levels playing an additional role in biomass and flower production. The role of propagule pressure was neglegible, especially towards later stages of invader development. We thus argue that mountains are likely to see rapid increases in plant invasions in the near future, as disturbance and human influence are on the rise in mountains. Our results however suggest that invasion is unlikely if both conditions are not met, suggesting that we might be able to keep undisturbed mountain areas invasion free. It will thus be a question of limiting the uncontrolled expansion of anthropogenic disturbance in mountains to contain mountain invasion within reasonable limits.