Sustainability in multi-aged stands: an analysis of long-term plenter systems

Long-term research plots in multi-aged stands managed with the plenter system were assessed to evaluate sustainability of the plenter system in Central Europe. Plots primarily consisted of Norway spruce (Picea abies (L.) Karst., silver fir (Abies alba Mill.) or European beech (Fagus sylvatica L.) and were measured for seven to 16 measurement intervals over 60-91 years. Sustainability was assessed with four types of criteria: stand density, tree species diversity, basal area increment, and stand structure. Comparable even-aged stands were also analysed to compare and evaluate the performance of the measures of sustainability. Measures of species diversity, increment and stand structural diversity generally experienced increasing trends over time in these even-aged stands. Basal area generally increased and trees ha(-1) decreased in multi-aged stands following similar patterns as in even-aged stands. These results suggest that the plenter system is still evolving and is not the model of sustainability often assumed. Many of the measures used have potential as indicators of sustainability in multi-aged stands.