Models for prediction of basal area mean diameter and number of trees for forest stands in south-eastern Norway

Basal area mean diameter and number of trees ha are important stand variabl es for projections made with large-scale forestry scenario models in Norway , The aim of this work was to develop models for an initial description of these variables. Multiplicative models. adapted to available variables from different types of inventories (relascope. photo and visual inventories) w ere developed, R-2 ranged from 0.85-0.87 in models where mean height by bas al area was available to 0.62-0.68 without this variable. Validations provi ded few statistically significant differences between predicted and observe d values, while the standard deviations for the differences were relatively large (7-43%). There are numerous sources of uncertainty in large-scale fo restry analyses, but the developed models will probably produce a satisfact ory standard of accuracy at an aggregated level. However, the large standar d deviations, and large consequential losses in terms of net present value applying the models, indicate that one should avoid relying solely on the m odels with respect to decisions at stand level.