Testing a new competition index for Maritime pine in northwestern Spain

A distance-independent competition index is derived from the basal area in larger trees (BAL) index combining individual tree's basal area percentiles with a relative-spacing stand-density measure. Empirical increment data fr om Maritime pine trees (Pinus pinaster Ait.) sampled from regular, naturall y regenerated stands in the province of Pontevedra, northwestern Spain, are used to compare the performance of the two competition indices in the cont ext of basal area growth modelling. The basal area increment of individual trees was first predicted exclusively as a response to competition using a two-parameter exponential function and then as a function of potential grow th reduced by competition. For the criteria evaluated in this paper the new competition index has shown superior qualities. The main improvement over BAL is the incorporation of the relative spacing measure.