Puettmann, Klaus JReich, Peter B2016-03-152016-03-151995The differential sensitivity of red pine and quaking aspen to competition. (1995). Canadian Journal of Forest Research, 25(11): 1731-1737, 10.1139/x95-187.https://hdl.handle.net/11299/178308Growth of red pine (Pinusresinosa Ait.) and quaking aspen (Populustremuloides Michx.) target trees with varying degrees of competition by neighboring aspen was measured in a 7-year-old clearcut in northeastern Minnesota. Competitive conditions were measured using indices of resource availability (percent open sky) and neighborhood stand density. Three-year diameter growth of target trees was reduced by more than 50% in both species because of competition from neighboring quaking aspen. The last 2 year's height growth was also reduced by approximately 30% for both species. The relationship between growth and percent open sky was convex for red pine and concave for quaking aspen, potentially indicating a greater sensitivity in aspen to any reduction below optimal resource availability. Competition reduced crown size in both species, but self-pruning occurred only in quaking aspen. Needle and leaf size were not affected by competition, but red pine needle density was lower in highly competitive environments. Red pine had a higher specific gravity when growing under competition, partially offsetting the reduction in wood volume.enArticle10.1139/x95-187