EVALUATION OF COMPETITION INDEXES IN INDIVIDUAL TREE GROWTH-MODELS

In this paper we explore how well distance-independent competition mea sures explain variation in the height and diameter squared growth of i ndividual conifer trees. We investigated a number of stand-level densi ty indices and individual tree competition indices which incorporate t ree sizes, but do not include location. We model growth of individual trees as potential growth reduced by competition. The reduction in mea n square error relative to no competition index was used to judge perf ormance of each competition index which varies by species and growth c omponent (height or diameter squared growth). Results are summarized b y species and type of competition index. The distance-independent meas ures are also compared to selected distance-dependent measures shown i n recent research work to perform well for conifer species. It was fou nd that a new class of distance-independent indices that includes esti mated crown parameters performs on par with the best distance-dependen t competition indices when used in conjunction with models of individu al tree height and diameter squared growth.