TAILIEUCHUNG - Báo cáo khoa học: "The effect of phase change on annual growth increment in eastern larch (Larix laricina (Du Roi) K. Koch)"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "The effect of phase change on annual growth increment in eastern larch (Larix laricina (Du Roi) K. Koch). | 171s Ann. Sci. For. 1989 46 suppl. 171S-177S Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA The effect of phase change on annual growth increment in eastern larch Larix laricina Du Roi K. Koch M. Greenwood Department of Forest Biology University of Maine Orono ME 04469 . Introduction Under natural conditions a plot of the cumulative height and diameter growth by dominant trees in a given stand exhibits a sigmoid growth curve with the maximum annual increment occurring relatively early in the age of the tree Assmann 1970 Fig. 1B . The time at which the maximum increment occurs appears to be speciesspecific and occurs earlier for pioneer species like pine see Fig. 1A . Such observations have led some growth and yield scientists to conclude that a tree undergoes several distinct growth phases during its development in a stand referred to as physiological ageing . Assmann 1970 . For example a phase where annual increment reaches a maximum value the phase of full vigor according to Assmann followed by a so-called mature phase where annual increments decline then stabilize have been proposed but the role of tree size or maturation state as a basis for these phases is not discussed. Assmann 1970 using data from von Guttenberg 1885 showed that for Norway spruce the maximum annual increment for both height and diameter occurs later on relatively poorer sites Fig. 1A and B . The trees were approximately the same height 7-8 m when the maximum increment occurred but the tree on the moderate quality site attained this height at age 34 compared with age 23 on the top quality site. Diameter growth increments appeared to follow a pattern similar to that for height growth. One interpretation of these observations is that annual increment is in part determined by the maturation state of the tree which in turn is a function of size not chronological age. The decline in annual increment will also be affected by competition from other trees for light water and .

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