Management options for the conversion of allochthonous coniferous forest patches towards more natural species composition in the Vorpommersche Boddenlandschaft National Park, NE Germany

Abstract

The conversion of coniferous tree plantations towards natural self-regenerating forests is one of the targets of forestry in Europe and particularly desirable in national parks. The aim of this study was to evaluate the effectiveness of different conversion approaches (conducted once) on natural forest development in man-made spruce plantations. We studied the effects of three distinct management options (partial-cutting [PC], clear-cutting with timber removal [CC] and clear-cutting with timber remaining [CCr]) six years after application on tree regeneration (sapling identity, abundance, height, browsing intensity) and understorey species composition in former spruce plantations within the Vorpommersche Boddenlandschaft National Park in Northeastern Germany. An unmanaged spruce [M] and near-natural beech [N] stands were considered as local references. The sites differed significantly in tree regeneration and understorey species composition. The abundance of native tree saplings was highest at site CCr, their height did not differ among sites, while browsing intensity was most pronounced at site CC. Understorey species composition of all management options was equally dissimilar to site N. However, site CCr contained more species that are typically abundant in local beech forests. Clear-cutting of spruce plantations with dead wood remaining on site favoured the natural regeneration of native trees and understorey vegetation compared to clear-cutting with timber removal, partial-cutting and no management. Herbivore browsing detrimentally affected tree regeneration independent of the treatment. Clear-cutting with timber removal promoted the dominance of competitive herbaceous species that may hamper long-term forest regeneration. We conclude that progression of site CCr appears to proceed fastest towards natural forest conditions. Further long-term data is required to derive clear trends regarding time and direction of forest regeneration.  Keywords: forest conversion, spruce plantations, beech forest, natural tree regeneration, understorey species composition, deer browsing