Boreal and subarctic dwarf shrub contribution to carbon capture early in the growing season

In boreal and subarctic regions, dwarf shrubs may dominate the ground cover in forests as well as open habitats. Therefore, their contribution to the carbon capture in these areas is important to quantify. The length of the growing season impacts greatly on the carbon capture and is also very variable depending on duration of the snow cover as well as daylenghts and temperatures. In a project studying many ecological aspects of dwarf shrubs in four sites in Norway, we compare a coastal and an inland site in the south and the north of the country. The coastal sites typically have less snow than the inland sites, whereas the southern sites have higher mean air temperatures than the northern sites. The extremes of these four sites are then the southern coastal site where the snowless season with favourable temperatures can come in April, versus the northern continental site where snowmelt and favourable temperatures may come in June when there is midnight sun. If the plants from varying locations are differently adapted to start photosynthesising and producing new leaves, it will impact on the seasonal carbon capture. To compare these abilities between sites, we collected plants from each site and grew them in controlled conditions giving them the same winter and spring startup conditions. The dwarf shrubs Calluna vulgaris and Empetrum nigrum are among the species we studied. Repeated measurements of photosynthesis rate, respiration rate and branch lengths were done to investigate the phenology. This presentation will show how the species differed between sites of origin and the results will be discussed with respect to the normal climate at each site.