tailieunhanh - Báo cáo khoa học: "Performance of young jack pine trees originating from two different branch angle traits under different intensities of competition"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: Performance of young jack pine trees originating from two different branch angle traits under different intensities of competition. | 635 Ann. For. Sci. 57 2000 635-649 INRA EDP Sciences Original article Performance of young jack pine trees originating from two different branch angle traits under different intensities of competition Guy R. Larocque Natural Resources Canada Canadian Forest Service Laurentian Forestry Centre 1055 du . . Box 3800 Sainte-Foy Quebec Canada G1V4C7 Received 16 June 1999 accepted 5 June 2000 Abstract - The performance of young jack pine Pinus banksiana Lamb. trees originating from seed orchard trees of two different branch angle traits was examined under different intensities of competition with morphological measures of crown development and growth efficiency measures. Seedlings were planted under a split-plot design at five initial spacings - m m m m and m - three blocks two branching characteristics and four replicates. Relative growth rate for diameter at breast height dbh increased by nearly twofold from the closest to the largest spacing. Crown width crown ratio needle density ratio and leaf weight ratio decreased significantly with decrease in spacing which indicated that the efficiency of jack pine crowns to occupy their growing space and the proportion of photosynthesizing biomass relative to respiring biomass were negatively affected by competition. Needle nitrogen concentration decreased with decrease in spacing and was significantly related to leaf weight ratio. Variation with tree size in the ratios of dbh increment to needle biomass and to needle nitrogen content indicated that small trees produced stemwood per unit of photosynthetic tissue and per unit of nitrogen more efficiently than large trees in the absence of severe competition and that this trend was gradually reversed as the intensity of competition increased. Branch angle trait did not constitute a significant advantage for crown development and stem growth. competition growth efficiency measures branch angle nitrogen Résumé - Performance de jeunes pins gris issus de