04 – Nagel

The tradition of long term forest experiments started in 1873 with a manual for thinning experiments published by the Society of German Forest Research. Many of these experiments are still in observation and have been used to understand the principles of forest growth, to test hypothesis, to derive models for sustainable management and to give advice to forest managers. Since the 1970s many permanent forest inventories have been established to describe the forest on a national, regional or company level. The availability of growth information from inventory data puts the amount of the long term experiments into question. The main difference between both sources of information is that long term experiments are designed to study cause and effects by active variation of one variable. Inventories are made to estimate unbiased the state or the change of a variable of interest, in example the standing volume or the volume growth. Inventory data represents usually average conditions and rarely extreme conditions which are important for understanding and modelling. However long term experiments are expensive in time and effort. Therefore, it is often not possible to establish the experiments on wide amplitude of site conditions. The use of existing inventory data in combination with long term experiment is a possibility to enlarge the data base and derive fast results for current issues. For example Albert and Schmidt (2010) used this approach to model climatic effects on the site index of Norway spruce and European beech. Long term experiments will still be essential for forest research. Available inventory data can be useful to fill in data gaps and to project the long term experiment results to a regional or overall site level.