Changes of Forest Stands Vulnerability to Future Wind Damage Resulting from Different Management Methods

The structure of forests stands changes continuously as a result of forest growth and both natural and anthropogenic disturbances like windthrow or management activities – planting/cutting of trees. These structure changes can stabilize or destabilize forest stands in terms of their resistance to wind damage. The driving force behind the damage is the climate, but the magnitude and sign of resulting effect depend on tree species, management method and soil conditions. The projected increasing frequency of weather extremes in the whole and severe storms in particular might produce wide area damage in European forest ecosystems during the 21 century. To assess the possible wind damage and stabilization/destabilization effects of forest management a number of numeric experiments are carried out for the region of Solling, Germany. The coupled small-scale process-based model combining Brook90 [1] and SCAlar DIStribuiton turbulence model [2-4] is implemented. The SRES climate scenarios A1B and B1 dynamically downscaled by Climate Local Model CLM [5] are used to project the future climate conditions in the area. The experiments are performed for two tree species (spruce and beech) and a mixed stand and for two target diameter harvesting scenarios. The results show considerable increment of wind damage risks towards 2100 compared to “present climate conditions”, caused by the combination of weak increase of wind speed and precipitation and strong increase of air and soil temperature. The effect is stronger for coniferous species than for deciduous ones. It is shown that management activities have a strong destabilizing effect on forests due to joint influence of climatic factors and decrease of stand density.