Site preparation of abandoned fields and early establishment of naturally and direct-seeded birch in Sweden

Karlsson. A. 1996. Site vrevaration of abandoned fields and earlv establishment of naturallv and direct-seeded birch in Sweden. Studia Forestalia Suecica 199, 25 pp. ISSN 0039-3150, ~ S B N 91-576-5152-3. Field experiments were carried out at four sites in Sweden to investigate the possibility of establishing downy birch (Betula pubescens Ehrh.) and silver birch (Betula pendula Roth) on abandoned fields by natural regeneration, direct seeding or both. The effects of six soil preparation methods on the vegetation cover, seedling survival, dominant seedling height and seedling establishment were studied up to four years after seedling emergence. The methods were: no preparation, ordinary ploughing, rotary cultivation, deep ploughing, soil inversion, removal of topsoil. Five additional treatments were applied: no treatment, herbicide, peat litter, wood ashes, slaked lime. Both a split-plot design and a randomised complete block design were used. Seedling survival and establishment without preparation, and with rotary cultivation, were close to nil, while the other soil preparation methods generally were more effective. Best seedling survival and establishment were obtained on seedbeds created by removing topsoil or by transposing it by deep ploughing or inversion. These seedbeds also suppressed competing vegetation, compared to seedbeds with topsoil at the surface. Seedling establishment after removal of topsoil, amounting to 8% of sown germinable seed, was outstanding on sandy soil, but much poorer on silty soil. The tallest dominant seedlings were found on seedbeds with topsoil within the soil profile. Application of peat litter to the seedbed promoted seedling establishment.