Adapting an Individual Tree Growth Model for Pure and Mixed Species Stands : Forest Ecosystem Restoration. Ecological and Economical Impacts of Restoration Processes in Secondary Coniferous Forests

2000

S. 54-60

5 Abb., 13 Lit. Ang.

Unselbständiges Werk

200072856

Within the Special Research Program (SRP) "Forest Ecosystem Restoration" the existing individual tree growth model PROGNAUS will serve as a link to other project parts dealing with the evaluation of the economic aspects of restoration. PROGNAUS is a basal area increment model for individual trees, that is based on a logarithmic function of tree size, competition and diagnostic site variables. The model coefficients have been estimated using data from the Austrian National Forest Inventory. The examination of 60 sample plots showed that the increment of spruce (Picea abies L. Karst.) in pure spruce stands was overestimated by the model and underestimated in mixed species stands. To verify whether the ecological differences between mixed and pure stands could be expressed in PROGNAUS, the original model was changed by adding basal area pro-portion of spruce as a new variable. By stepwise regression, the model was re-parameterised including interactions between physical and chemical soil parameters, growth variables and spruce proportion. The same was found when using the data of the Austrian Forest Inventory. Furthermore it was found, that up to a certain breast height diameter, individual tree growth of Norway spruce is better in pure stands than in mixed stands, depending on competition.