Establishing mixed forests in Sweden by combining planting and natural regeneration—Effects of shelterwoods and scarification

Abstract

This study investigated the combination method which is defined as a method where natural regeneration of Scots pine ( Pinus sylvestris L.) is combined with planting of Norway spruce ( Picea abies L. Karst.). An experiment with planting of Norway spruce seedlings with and without soil scarification in shelterwoods of Scots pine and on clearcuts was established on 22 sites in southern, central and northern Sweden. Survival of Norway spruce and density of Scots pine was higher in shelterwoods than on clearcuts whereas height growth of Norway spruce, Scots pine and birch ( Betula pendula Erh. and Betula pubescens Roth.) was lower in shelterwoods. Survival and height of planted Norway spruce, density and height of naturally regenerated Scots pine and density of naturally regenerated broadleaved species were positively affected by scarification. Naturally regenerated Scots pine seedlings were small in comparison to planted Norway spruce seedlings 5–8 years after planting. This was most evident in southern Sweden where the height difference between the planted Norway spruce and naturally regenerated Scots pine was too large for pine to be a part of the future stand.