Immediate effects of four different felling methods on mature boreal spruce forest understorey vegetation in southern Finland

We investigated the immediate response of mature (mean stand age 102 years) boreal spruce forest understorey vegetation to four different felling meth ods on 1-ha study plots in southern Finland. We hypothesized that understor ey vegetation response depends on the intensity of the felling method. Vege tation was sampled before the treatments and the year following them, when resident understorey vegetation had not had time to recover from the distur bance and pioneer species were still scarce or absent. Response of understorey vegetation differed significantly between the treat ments. Bryophyte species number decreased significantly in single-tree sele ction system felling (33% of stand volume felled). retention Felling (93% f elled) and standard clear felling, but remained at the pre-treatment level in gap felling (50% felled) and in control plots. Bryophyte cover decreased significantly over all treatments, except the residuals of the gap felling and the controls. Number of vascular plant species decreased significantly only in clear felling and retention felling, while cover of vascular plant s decreased significantly in all treatments, including controls. Vegetation response to gap felling and single-tree selection system felling was rathe r similar at the stand level. However, there were significant differences b etween the felled areas and residuals in gap felling in post-treatment vege tation species composition and cover. Retention felling and clear felling d id not differ significantly from each other in terms of vegetation response . Apparently the residual tree groups, which contained 7% of the pre-treatm ent stand volume, were too small to have significant sheltering effect on l ate successional vegetation in or outside of residuals. (C) 2001 Elsevier S cience B.V. All rights reserved.