SITE INDEX AND PRODUCTIVITY OF ARTIFICIALLY REGENERATED BETULA-PENDULA AND BETULA-PUBESCENS STANDS ON FORMER FARMLAND IN SOUTHERN AND CENTRAL SWEDEN

Site index and productivity of artificially regenerated stands of silv er birch (Betula pendula Roth) and downy birch (Betula pubescens Ehrh. ) on former farmland in southern and central Sweden were examined. The material comprised sample plots in 27 stands, measured in both 1990 a nd 1993. Silver birch was the dominating species in most stands, and t he average site index (SI) was nearly 28 m. Site quality ranged from 5 .3 m(3) ha(-1) yr(-1) (equivalent, from tables, to a SI of 22 m) to 11 .4 m(3) ha(-1) yr(-1) (equivalent to an extrapolated SI of 32 m). Soil moisture was the only site factor tested that significantly affected SI for silver birch. Moist sites were found to be inappropriate for th is species especially on fine-textured sediment soils. On moist sites, SI for downy birch was as high as SI for silver birch. Growth of arti ficially regenerated silver birch on former farmland differed signific antly from growth of naturally regenerated birch on forest sites, acco rding to two Swedish growth simulators.