BFW
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    User Interface from the Software PROGNAUS |
Modelling Forest GrowthFollowing a North-American trend of the 1970s, individual-tree growth models have been developed in Europe within the last two decades. These models are considered as alternative management tools replacing the classical yield tables. One of the benefits of individual-tree growth models is that they in fact predict the growth of individual trees. In contrast, yield tables are only reproducing the development of stand characteristics such as stem number, basal area and volume per hectare as well as mean diameter, mean height and dominant height. Because of this capability individual-tree growth models provide more detailed information about stand structure (e.g. diameter distribution, tree species composition), which becomes increasingly important due to a general trend to individual-tree based forest management.The core module of such an individual-tree growth model is a set of species specific mathematical (statistical) functions predicting diameter and height increment as well as the probability of mortality. Many of the individual-tree growth models also include functions describing the regeneration of young trees. The coefficients of the functions are usually estimated from a large and representative data set using multivariate statistical methods. All these models operate on the level of individual trees. Thus, it is possible to describe the effects of many silvicultural management systems, different tree species compositions and age-class distributions. At the Institute of Forest Growth Research, University of Natural Resources and Applied Life Sciences (BOKU), Vienna, Austria, ord. Univ. Prof. Dipl.-Ing. Dr. Hubert Sterba developed the distance-independent individual-tree growth model PROGNAUS. Under his supervision the model was continuously improved and extended. The data for estimating the model coefficients were provided by the Austrian Federal Office and Research Centre for Forests (BFW), Department of Forest Inventory. PROGNAUS has been validated several times in cooperation with the Department of Forest Growth and Silviculture (BFW) using data from permanent research plots, and it has successfully been applied for a prognosis of the timber supply in Austria. Within the scope of the EU-Project ITM, which was coordinated by ao. Univ. Prof. Dipl.-Ing. Dr. Hubert Hasenauer, the forest growth model PROGNAUS was implemented in the Forest Growth Simulator PROGNAUS for WINDOWS 2.3 by Dipl.-Ing. Dr. Thomas Ledermann. The activities in forest growth modelling at the BFW are mainly limited to the application and evaluation of PROGNAUS. Additionally, it is intended to check out new fields of model application. In particular, within the scope of a new research focus we are going to test whether the model concept is suitable for describing the dynamics of stand structure and regeneration in protection forests. Moreover, this new research focus should also help us to better understand the relationships between regeneration, growth and mortality of individual trees growing in high elevation forests. From this knowledge guidelines for an appropriate silvicultural treatment of protection forests should be deduced. |
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