Testing a new competition index for Maritime pine in northwestern Spain

distance-independent competition index is derived from the basal area in larger trees (BAL) index combining individual treeʹs basal area percentiles with a relative-spacing stand-density measure. Empirical increment data from Maritime pine trees (Pinus pinaster Ait.) sampled from regular, naturally regenerated stands in the province of Pontevedra, northwestern Spain, are used to compare the performance of the two competition indices in the context 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 growth 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.