Comparative responses of phenology and reproductive development to simulated environmental change in sub-Arctic and high Arctic plants

A high arctic polar semi-desert community is characterised by a sparse, low and aggregated vegetation cover where plant proliferation is by seedlings. A sub-arctic dwarf shrub heath is characterised by a complete vegetation cover of erect, clonal dwarf shrubs which spread vegetatively. At the polar semi-desert site, there was a striking effect of temperature enhancement treatments on phenology and seed-setting of Dryas octopetala ssp. octopetala, with almost no seed-setting occurring in plots experiencing ambient temperatures. There was no significant effects of temperature enhancement alone on fruit production of Empetrum hermaphroditum at the sub-Arctic dwarf shrub heath site, although fruit production was significantly influenced by application of nutrients and/or water. The response of a dominant high arctic dwarf shrub to increased temperature suggests that any climate warming may stimulate seed-set. This could be particularly important in the high Arctic where colonisation can proceed in areas dominated by bare ground and where genetic recombination may be needed to generate tolerance to predicted changes of great magnitude. In the sub-Arctic, however, the closed vegetation is dominated by clonally-proliferating species and recruitment from seedlings is rare. Plant fitness will increase here in response to any increased vegetative growth resulting from higher nutrient availability in warmer organic soils. -from Author