Concerns over sustainability and a move towards systems of forest management other than clearfelling have fuelled the search for flexible growth models that can be used in a wide variety of situations with wide generalisation. The Tyfiant Coed project was established to develop a distance dependent individual tree model based on earlier stand level approaches. The model is parameter parsimonious and the parameters are interpretable. ln particular the primary growth parameter, c₁, is considered to reflect the vitality of a tree and is itself influenced by competition factors and environmental conditions. After preliminary parameterisation work using German data, Tyfiant Coed has attempted to establish suitable parameters for a flexible growth and yield model for
Sitka spruce (Picea sitchensis (Bong.) Carr.). This study describes methods of collecting data suitable for the establishment of model parameters and initial investigations into the relationship of the parameters with broad environmental variables. A rapid method was used to gather data from a wide variety of site types in north and mid Wales. Using these data alternative parameter values for individual trees and stands were estimated. These parameters were compared to values derived from stem analysis. The ability of the model to reproduce the pattern of individual tree growth was also examined. Using linear regression techniques parameter values were compared with environmental factors to determine whether any relationships existed.
The suitability of the methodology and its potential for use in modelling in Britain are discussed. Suggestions for further work are made.