Limits to plant invasions at the edge of the Arctic

Abstract

Invasions by non-native plants are a widespread and serious problem throughout temperate regions, but invaders remain scarce in arctic and subarctic ecosystems. Northern limits of invaders may be set by environmental barriers; however, these barriers have rarely been studied in northern Canada. Churchill, Manitoba (58ºN) represents a unique site for northern invasion research, where over a hundred non-native plants have been recorded. While some have persisted for decades in human-disturbed areas, none have spread into nearby tundra ecosystems. Reasons these non-natives have failed to spread remain unclear.

We conducted field surveys, soil sampling, transplants, and common garden experiments to test the importance of various potential barriers to northern invasions. Results found that soils collected from invaded areas contain a high proportion of non-native seeds, potentially contributing to local persistence and spread. Non-native species had low survival and performance when transplanted into the tundra, suggesting that requirements to invasion success are not met. However, transplants performed better when transplanted with soil collected from previously invaded sites, suggesting that belowground factors may play an important role in invasion. Finally, sheltered sites, such as the south side of buildings, favour the survival of non-native species, perhaps because of a warmer microclimate.

These results suggest that the current failure of non-native species to spread into the natural environment is due to the inhospitality of the subarctic. However, if these invasion barriers are removed (i.e., elevated temperatures, increased soil nutrients), there is a risk of non-native species invasion from human-disturbed areas into the surrounding tundra.

Vicki M. Zhang

PhD Candidate

I am a PhD Candidate at UofT studying invasive species in the subarctic, and am passionate about science communication and outreach.