Growth performance of two deciduous Vaccinium species in relation to nutrient status in a subalpine heath

Net primary production (NPP) of two Vaccinium species (V. myrtillus and V. uliginosum) was determined in three subalpine heath communities on the Northern Apennines (N. Italy). The main objective of the study was to test the hypothesis that two species sharing the same plant functional type (deciduous dwarf shrub) have similar growth performances along environmental gradients. The second objective was to assess whether, and to what extent, NPP of the two species was associated with functional and morphological traits, which can affect plant growth in relation to nutrient status. Total community NPP in the three communities was closely related to soil nutrient availability. NPP of V. uliginosum did not vary among communities, while that of V. myrtillus peaked in the most fertile habitat. The N:P ratio in the whole plant as well as in the leaves of the two shrubs exactly mirrored the among-community pattern in soil phosphate concentration. In particular, the foliar N:P ratio in both V. uliginosum and V. myrtillus was >16 in the poorer sites, which indicates P limitation. I concluded that the growth response of the two shrubs in relation to soil nutrient availability is individualistic. Growth of V. myrtillus is P-limited while that of V. uliginosum is not.