Natural Regeneration of Broadleaved Tree Species in Southern Sweden

Karlsson, LT. 2000. X f . i m r m . L usgenerulion oJ'hroadleaved lree .species in .soulhern Sweden EJJerls o$ . s i l v i r d f u m l ireafment.s mnd .seed disprsa l f rom surrounding .slnnds. Doctor's dissertation. ISSS 1401-67307 ISBN 91-576-6080-8 The objective of the present thesis was to examine the effects of silvicultural treatments and seed dispersal from surrounding stands on the establishment of natural regeneration of broadleaved tree species in southern Sweden. Most of the broadleaved tree species that occur naturally in forests in southern Sweden were studied but birch (Betulapendula Ehrh.1 B. pi~besceizs Roth) was the most common species and present in equal numbers in all studies. The wind dispe.rsa1 of see.ds of se.ven species was studied and great variations were found. This could mainly be explained by differences in seed morphology. The effect of soil scarification was examined in all five studies and was generally found to be positive for the establishment of the studied broadleaved species. However, in some cases the scarification was not positive for the establishment. The reason for t l i s was hypothesised to be that the seed supply was limited, or an effect of large and/or animal-dispersed seeds. The effect of shelterwood w a s examined in three studies and was found to be positive for animal-dispersed species but negative for shade-intolerant species, although a sparse shelterwood can be used to rcgcncratc birch. Slash removal was included in onc study and found to be positive for thc cstnblishrncnt of birch. This thcsis showccl that regeneration trcatmcnts can be used to incrcasc the e.stablishnent of naturally regene.rated broadleaved tree seedlings, but the stand structure and species composition must be regulated with pre-commercial thinning. However, the effect of variations in seed production and seed dispersal must be closely examined from a time and a space perspective prior to any forecasts regarding the effects of regeneration trcatrncnts. Keynwds: Broadlea ed tree species. Establishment, Natural Regeneration, Scarification, Seed dispersal, Shelterwood, Silr, icultuial treatments. iliithorr's adre\\. hlat ts Karlsson, Swedish University of Agricultural Sciences, Southern Snedish Forest Research Centre. P.O. Box 49. S-230 53 Alnarp, Sweden. E-mail: Matts.Karlsson@ ess. slu. se