SOIL SEED BANKS IN PRIMARY AND SECONDARY DECIDUOUS FOREST IN BIALOWIEZA, POLAND

Germination over 3 years was followed in 25 soil samples of 31 x 31 x 5 cm each from primary and secondary stands in Bialowieza forest, Pola nd. The number of seedlings emerging and the number of species decline d over the 3 years. In year 1 the mean densities of emerging seedlings for the primary and secondary stands were similar (2142 m(-2) and 248 8 m(-2) respectively); in year 3 the difference was greater (248 vs 49 8 m(-2)) but not statistically significant. The trend reflected the gr eater longevity of the seed bank species characteristic of the seconda ry forest. Two functional groups of herb and shrub species were distin guished in the seed bank based on (a) frequency as adults in the prese nt vegetation, and (b) relative abundance in the seed banks of primary and secondary forest. Group A species need large-scale gaps in the tr ee canopy; most have very small seeds (<0.15 mg mean dry mass) and are very persistent in the soil. Group B species benefit from single-tree fall gaps in the tree canopy, but appear to be suited primarily to gap s in the canopy of the herb layer and in the root layer made mainly by animals; their seeds are not as small (mostly >0.15 mg) and not as pe rsistent in the soil. Group B species made up 86% of the seedlings eme rging over 3 years in soil from the primary stand, and 56% of those fr om the secondary stand. In the laboratory all five Group B species tes ted showed some inhibition of germination in darkness, but only one sh owed unequivocal inhibition by far-red-enrichment of low irradiance li ght.