Abstract
Biological invasions are a global problem, but invasions are relatively rare at high latitudes. This is starting to change as non-native species are beginning to appear in these regions. Climate change and increases in human activity in polar regions are likely to exacerbate this issue. The northern town of Churchill, Manitoba offers an ideal site for research into this problem: its history as a rail link has provided a pathway for the introduction of non-native plant species, with dozens persisting for decades. None of these species has spread significantly beyond town boundaries, suggesting environmental conditions are limiting their range. Seed-contaminated soil may be a potential avenue for spread, but seed germination and establishment may be a bottleneck for invasions at high latitudes. My field experiments investigated if changes in temperature, snow cover, and seasonal timing of germination could increase the germination and growth of non-native plants from seeds in contaminated soil. My results suggest an earlier start to the growing season could increase the germination of some non-native species, while warmer temperatures increase their growth and reproductive output. However, snow cover or warmer temperatures may not affect the germination of all non-native species in the same way. This indicates that future climatic warming risks improving some components of the performance of invasive species, potentially accelerating the rate of invasions.