Intra-specific variation in phenology offers resilience to climate change for Eriophorum vaginatum

Phenology of arctic plants is an important determinant of the pattern of carbon uptake and may be highly sensitive to continued rapid climate change. Eriophorum vaginatum has a disproportionate influence over ecosystem processes in moist acidic tundra, but it is unclear whether its growth and phenology will remain competitive in the future. We asked whether northern tundra ecotypes of E. vaginatum could extend their growing season in response to direct warming and transplanting into southern ecosystems. At the same time, we asked whether southern ecotypes could adjust their growth patterns in order to thrive further north, should they disperse quickly enough. Detailed phenology measurements across three reciprocal transplant gardens and two years showed that some northern ecotypes were capable of growing for longer when conditions were favourable, but their biomass and growing season length was still shorter than the southern ecotype. Southern ecotypes retained large leaf length when transplanted north and mirrored the growing season length better than the others, mainly due to immediate green-up after snowmelt. All ecotypes retained the same senescence timing, regardless of environment, indicating a strong genetic control. E. vaginatum may remain competitive in a warming world if southern ecotypes can migrate north