SEED BANK COMPOSITION IN A SUB-ARCTIC 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 x 12 cm) were taken from plo ts that had received sulphuric acid and (or) nitric acid irrigation of pH 3 for 5 years and from irrigated control plots. The average seedli ng density per plot calculated from seedbank samples was 912/m2, varyi ng from 191 to 5240. All the main aboveground taxa were present in the emerging seedlings with Betula sp. and Empetrum nigrum ssp. hermaphro ditum being dominant. Other common seed-bank species included Vacciniu m uliginosum, Vaccinium vitis-idaea, and Festuca ovina. Acid treatment did not have any significant impact on the composition of the seed ba nk 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.