Invasive plant species cause ecological or economic harm in a new environment where they are not native. Invasive species compete with native species for resources and alter whole habitats. Climate change is expected to change the competitive ability of both native and invasive species. Much attention has been paid to how longer growing seasons affect plants, but the effects of warming winters has rarely been addressed.

Lupinus polyphyllus is a perennial nitrogen fixing legume that colonizes dry meadows and road verges in Finland. Being a strong competitor, Lupinus threatens native species and reduces biodiversity. Currently, we are studying the responses Lupinus to warm winters in a mesocosm experiment. Mesocosms consisting of 12 herbaceous species were established in summer 2016. In spring 2017, Lupinus will be introduced in half of the mesocosms. The mesocosms will be grown at the Viikki Campus, Helsinki, during the growing season. For the winter season, the mesocosms will be transferred either to a maritime overwintering site with mild winters and ephemeral snow (Åland Islands), or to a continental overwintering site with cold climate and persistent snow cover (Lammi, southern Finland). As the mesocosms will be returned to their original site in the beginning of the following growing, we are manipulating only the overwintering climate of the plants. Both short-term and long-term responses will be monitored.

Lupinus polyphyllus, Photo: Timo Saarinen