Mechanized Harvesting Systems in Permanent Stands and Technology

The application of different modern logging systems depends on the silvicultural aims and methodologies. Depending upon these specifications the appropriate technique must be selected. This is the basic condition, which leads to a specific logging system in Central European and especially in German forestry. In the following an overview is to be given upon the different applications of full-mechanized harvesting systems in permanently managed forests in Germany. First of all the principles of sustainable silviculture are explained. Afterwards the advantages of modern Harvesters and Forwarders and their limitations under given conditions are discussed. Further an idea of the ecological effects for stock and soil, caused by the use of heavy logging machines, is to be given. SILVICULTURAL BASICS The principles of silviculture in Germany and especially in the southwest of BadenWuerttemberg are shaped through the natural essentials and small scale forestry. These are the main reasons for the fact that the forests are managed as continuous forests. In more recent time the realization is added, that forests cannot only serve pure wood production, but have also an ecological meaning and have to serve as a recreation region too. Due to high population density in Germany it is not possible to separate these different requirements, the same forest area has to fulfill all requirements at the same time. Outgoing from this starting situation it becomes obvious that an clear cut on large surface (> 1 hectare) forbids itself. From traditional forest forms of management and the requirements of the society to the forest, the silvicultural target finally results as continuous forest. The management of a continuous forest is shaped by the fact that trees of different ages and heights are present at the same time. Harvesting is done in all ages, heights and diameters. This type of silviculture causes permanent use of harvesting techniques, which can be quite problematic as described in the following. MACHINE USAGE IN THE CONTINUOUS FOREST The continuous forest management saves some problems for the forest technique. Despite the permanent crossing by logging machines it must remain ensured that the productivity of the soil and the stock is not impaired substantially. The largest influences on the stock are damages by cutting and skidding and compression of the soil body by crossing with heavy machines. In both cases substantial growth losses at the remaining stock can result from inappropriate application of harvesting techniques. This can go so far that stocks are destabilized and become susceptibly to various calamities (e.g.: Storm or bark beetles). The application of fullmechanized harvesting procedures in continuous forests is shaped additionally by the structures and especially the increased strong wood proportions.