EVALUATING THE IMPACT OF COMPETITION USING RELATIVE GROWTH-RATE IN RED PINE (PINUS-RESINOSA AIT) STANDS

The development of red pine (Pinus resinosa Ait.) stands originating in different spacings was analyzed using absolute growth rate (AGR) and relative growth rate (RGR) in diameter at breast height for several ages. The objectives were to determine whether RGR better reflected the effect of competition than AGR, and to interpret the relationship between RGR and tree size. While AGR was always positively related to tree size, RGR decreased with an increase in tree size before the onset of competition and when competition was not severe, and increased with tree size under severe competitive stress. This implied that small trees were more efficient than large trees at producing new biomass before the onset of competition. The effect of competition was to reduce the efficiency of small trees relative to large trees. It was concluded that RGR expressed the competitive status of stands better than AGR.