Epsilon Archive for Student Projects

Abstract

A national regeneration experiment was established across the boreal forest of Sweden. This study presents the regeneration results of the combination method, the so-called Drettinge method, which aims to evaluate the establishment of mixtures of naturally regenerated Scots pine (Pinus sylvestris L.) and planted Norway spruce (Picea abies L. Karst.). In the experiment, two different regeneration approaches were compared: (i) planting on clearfelled areas and (ii) a combination of planting and natural regeneration using shelter trees. About 133 stemsha-1 of Scots pine trees were retained in the shelterwood and no trees were retained in the clearcut. Planting was performed in both treatments with 2000 - 2500 Norway spruce seedlings ha-1. Each of the established plots was further divided into two sub-treatments, treated with either soil scarification or no soil scarification. Ten (10) sites across the south to central of Sweden were analysed for this study. Stem density, basal area proportions and volume production were analysed across the treatments in both regions. The results from this study show that the treatments resulted in a Norway spruce-dominated stand on the sites in the south. At the same time, the sites in the central region were mainly spruce-pine mixtures. Natural regeneration of birch was abundant in both regions. The volume production was similar to the basal area production in both regions. The shelterwood treatments resulted in lower basal area and volume in both regions. Scarification had a limited effect on the stand variables. The stands in clearcut treatments often outperformed the stands in the shelterwood treatments in both regions. Based on the results of this study, it is evident that the combination method was not successful in achieving the desired outcome of establishing mixed forests of Scots pine and Norway spruce, particularly in the southern sites. Consequently, there is a need for further development of the combination method to effectively promote the creation of mixed forests, thereby ensuring sustainable forest management practices.