Strukturvielfalt als Ergebnis waldbaulichen Handelns

The effect of silvicultural treatment on the spatial diversity of forest stands has hitherto rarely been examined on quantitative scale. The aim of this study is to quantify the effect of silvicultural treatment on the spatial heterogeneity and diversity of forest stands. One first important basis are indices that are capable of quantifying reliably horizontal tree distribution patterns, vertical stand profile and segregation of species. A second means of modeling the spatial stand structure and the stand dynamics is the stand simulator SILVA 2. By combining SILVA 2 with a programme module for structural analysis, we get a flexible prognosis and research tool with the help of which we can examine the influence of different regeneration technics, thinning regimes and site conditions on growth, yield and spatial stand structure. By a series of simulation runs, the influence of the initial structure (single and group mixture), thinning method (thinning from below and thinning from the top) and thinning degree (slight, moderate and strong) on the spatial structure of mixed stands of spruce and beech is examined. The indices for the horizontal distribution pattern, the vertical profile of the species and the segregation underline the fact that especially slight and moderate thinning from the top offer an effective possibility to form the stand structure and support its diversity. Thinning from below has a more homogeneous effect on the spatial stand structure. The desired integration of structural diagnosis and statements into prognosis models that hitherto have been aligned to wood yield exclusively offers the possibility of considering, quantifying and optimizing production and stability aspects of silvicultural treatment.