Response patterns of Vaccinium myrtillus and V. vitis‐idaea along nutrient gradients in boreal forest

The relationships between biomass of dwarf shrub species and nutrient gradients of forest soils was studied under field conditions in boreal forests. The biomass‐response curves of Vaccinium myrtillus and V. vitis‐idaea were fitted against soil nutrient gradients using Generalized Linear Models (GLM). Ecological niches of Vaccinium myrtillus and V. vitis‐idaea were evaluated, and effects of nitrogen addition (manipulation of the nutrient gradient) on response function were tested. The Vaccinium species showed statistically significant Gaussian responses along soil nitrogen, phosphorus and calcium gradients, but not along other gradients (K and Mg). Furthermore, manipulation of the nitrogen gradient seemed to have a minor effect on response functions, i.e. addition of nitrogen did not change ecological niches of these species. Ecological optima of V. myrtillus and V. vitis‐idaea on the nutrient gradients were about the same. This study suggests that differences in dominance between Vaccinium myrtillus and V. vitis‐idaea in boreal forest is not determined by nutrient gradients, but may rather be explained by light conditions and/or moisture availability.