Seed bank composition in a subarctic pine–birch forest in Finnish Lapland: natural variation and the effect of simulated acid rain

The seed bank composition and seedling densities were determined for a subarctic pine–birch forest. Samples (12 × 12 cm) were taken from plots that had received sulphuric acid and (or) nitric acid irrigation of pH 3 for 5 years and from irrigated control plots. The average seedling density per plot calculated from seedbank samples was 912/m 2 , varying from 191 to 5240. All the main aboveground taxa were present in the emerging seedlings with Betula sp. and Empetrum nigrum ssp. hermaphroditum being dominant. Other common seed-bank species included Vaccinium uliginosum, Vaccinium vitis-idaea, and Festuca ovina. Acid treatment did not have any significant impact on the composition of the seed bank or on germinative capacity in general. These findings indicate the existence of a viable soil seed bank in northern subarctic forests and the persistence of viability in spite of moderate acid deposition.