The influence of softwood broadleaves on vegetation and the soil organic layer in Norway spruce stands - investigations in a two-decade old birch-rowan forest in the upper Solling area, Lower Saxony, NW Germany.

摘要

Vegetation, stand structure, and organic soil layer of a birch-rowan (Betula pendula, B. pubescens/Sorbus aucuparia) forest on sandstone in the upper Solling area of NW Germany were studied. Twenty years previously, the Norway spruce [Picea abies] trees on the site had suffered windthrow, and were consequently cleared. Natural regeneration of pioneer broadleaves was largely undisturbed, and this development is analysed and discussed, in order to clarify the role of pioneer 'softwood' broadleaves onthe vegetation, structure and organic layer of stands which contain Norway spruce. Compared with a neighbouring remnant of a 100-year-old Norway spruce stand, the birch-rowan forest is more diverse in terms of stand structure and number of species. Significant changes were found in botanical composition and dominance of species in the herb and moss layer. High cover values of Avenella flexuosa [Deschampsia flexuosa] in the Norway spruce stand were replaced by Agrostis tenuis [A. capillaris] in the birch-rowan forest. The species which are more frequent in the birch-rowan forest than in the Norway spruce stand indicate the relatively higher light intensity on the forest floor, a higher nitrification rate in the upper soil and moist site conditions or temporary stagnating water conditions. Soil organic layer quality differed significantly between the two stands. In view of near-natural silviculture, the results show the positive effects of a temporary pioneer 'softwood' broadleaved stand on soil organic matter and ground vegetation of coniferous stands.