EVALUATING FOREST STRESS FACTORS USING VARIOUS FOREST GROWTH MODELINGAPPROACHES

This paper examines in detail the relative merits of several modeling approaches to evaluating forest site, physical, chemical and climatic stresses. The modeling approaches considered are (i) empirical growth and yield (management) models (STEMS and FOREST); (ii) successional mo dels (JABOWA/FORET gap-phase simulation models and FORSKA); (iii) fore st process models (FOREST-BGC). The models were analyzed in terms of t heir assumptions, formulation, and predictive ability. The analysis in corporated intensive measurements of tree growth and weather condition s taken over 7 years in two stands of northern hardwoods located in Up per Michigan (USA). The process model was very detailed and required m any input variables. All models performed poorly when predictions were compared with the observed data making accurate site-specific predict ions impossible without local calibrations.