Ertragskundliche Leistung in den Plenterwald-Versuchsflächen der Schweiz | Yield performance in the plenter forest research plots in Switzerland

Abstract

22 plenter forest research plots, some of which are under long-term observation, allow the assessment of the performance of these stands and to a certain extent these performances can also be compared with the perfor mances of other management systems. The performance descriptions presented here are in a broad sense of the term growth and yield: the pure growth parameters for four selected areas are complemented by a modelling of the economic results by determination of the timber harvesting costs and the revenues. Young forest surveys were also made in four areas and thus allow us a glimpse into the future development. Most of the areas presented here lie in the silver fir - beech belt, some in the upper montane and in the subalpine zone and only one in a stand rich of broad-leaved trees. An equilibrium model can be calculated for most of these stands. The high altitude areas, two stands with high volume retention and conversion stands were exceptions. These areas showed high fluctuations in the growing stock. In contrast the increment remains the same over a large range of the growing stock. Utilization and increment are on the average in a similar magnitude. Standing volume and heavy timber proportions are lower in higher altitudes due to site conditions. The modelled revenues after deducting harvesting costs can be partly correlated with the diameter of the mean basal area tree of the harvested logs. Based on the stem number distribution from the one year old plant to the thickest tree, the sustainability of the forest effects – timber extraction or protection – for four areas is assured in the future. It can be shown with this data that the big advantage of selection forests lays in the regularity of these performances and this also on small areas.