A study on the ecological significance of snow distribution in the low Arctic tundra plant communities of northern Fennoscandia
A combination of field/monolith-based experimentation and numerical modelling was used to study the short-term influence of snow distribution on various ecological/biogeochemical attributes of a range of contrasting Low Arctic tundra plant communities in northern Fennoscandia. Experimental snow augmentation delayed the timing of snow melt, postponing early-season phenological development in a number of plant species, but had no effect on average plot greenness. Significant changes in stem growth, branching, leaf growth, leaf nutrient content, flowering and fruit production were also observed in response to the artificial increases in snow cover. The responses were generally species-specific and in many cases were also dependent on the type of community. Advanced snow melt was also found to exert a species-specific influence on plant phenology, promoting earlier occurrence of initial phenophases. Complete prevention of winter snow cover on the other hand, exerted a retarding influence on plant phenology. Both increasing snow cover and removing it completely were found to reduce carbon turnover, but had negligible effects on net ecosystem CO2 exchange. However, turnover and net CO2 exchange were found to differ between communities, with model estimates suggesting that they were all CO2 sources of varying strengths during the course of the study (although errors were large). The CO2 model also demonstrated the importance of vegetation cover and phenology in determining annual ecosystem CO2 balance. Snow melt date (independent of energy balance) was found to be less important. The short-term effects of snow cover perturbation demonstrated here indicate a number of pathways by which snow may directly or indirectly (via modification of nutrient dynamics etc) influence the structure and functioning of tundra ecosystems. More detailed, long-term analysis is required however, to further elucidate the nature of these evidently crucial, yet complex snow-ecosystem interactions.