Low temperatures reduce establishment of new populations of invasive plants in a subarctic treeline environment.

Biological invasions are a serious global issue, but invasions are relatively less common at high latitudes, likely due to harsh environmental conditions and limited accessibility. An exception to this is human-settled and disturbed towns that may promote invasions and risk acting as sources of non-native species into the surrounding natural areas. For instance, Churchill, Manitoba, Canada (58ºN), is a treeline subarctic town and port connected by a railway to temperate North America. More than a hundred non-native plant species have been recorded within the town footprint and associated areas. While some have persisted for decades in these areas, none has spread into nearby tundra or boreal forest ecosystems. We used a greenhouse warming experiment to investigate the importance of increased growing season temperatures on three perennial non-native species (Linaria vulgaris, Plantago major, Taraxacum officinale), and used a transplant experiment to investigate non-native survival and growth after manual translocation to tundra and boreal forest roadside over several full years. We found that non-native plants were able to survive temporarily after manual translocation to roadsides adjacent to natural areas, with higher survival in warmer boreal forest roadsides. When we experimentally increased temperature, non-native seed germination increased, and non-native transplants trended toward increased survival and growth, again suggesting that temperature is a limiting factor. However, survival and growth of these non-native species consistently declined over time. Future global and climate change that results in increased warming therefore may shift these non-native species from invasion failure to success.