Seed banks at six open and afforested heathland sites in southern Sweden.
Germinable seed banks in the soil were determined for: a grazed heathland; 4 first generation Picea abies plantations age 30-73 yr; and one recently clear-felled area previously covered with an 85-yr-old first generation P. abies plantation. On the open heathland site, the top 6 cm of soil was estimated to contain 22 species with a total of 45 200 (s.e. 4200) seeds/m2, 88% being of Calluna vulgaris. The depth distributions of the predominant species down to 9 cm in the mineral soil varied greatly, although all species occurred through the whole sampled section, suggesting that many seeds were probably not recently deposited. The 4 P. abies plantations had fairly similar soil seed floras. Some 24 species were found, of which 15 had probably been stored in the soil since before afforestation. Most seeds were of Calluna vulgaris, with up to 26 000 (s.e. 2000) seeds/m2 down to 6 cm in the mineral soil. Carex pilulifera, with up to 2400 (s.e. 410) seeds/m2 and Juncus spp. with up to 780 (s.e. 250) seeds/m2. There was no trend in seed densities with stand age. On the clear-felled area, dense stands of Calluna and Carex pilulifera were present, but only in scarified patches of soil, showing that the seeds of certain heathland species may survive an entire forest rotation in the soil in numbers sufficient to be important for the revegetation after felling if the humus layer is disturbed.