tailieunhanh - Báo cáo khoa học: "The of 4 quality and wood properties provenances of South-African-grown"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: The of 4 quality and wood properties provenances of South-African-grown. | Ann Sci For 1994 51 203-212 2 03 Elsevier INRA Original article The quality and wood properties of 4 provenances of South-African-grown Pinus tecunumanii FS Malan Division of Forest Science and Technology CSIR Box 395 Pretoria South Africa Received 1st September 1992 accepted 25 June 1993 Summary The wood properties of 4 provenances of South-African-grown Pinus tecunumanii ie Yucul Camelias Mountain Pine Ridge and st Rafael were examined and compared with those of 3 commercial controls ie Pinus patula Pinus elliottii and Pinus taeda. Trials planted at 2 sites were evaluated. The rate of growth and stem form of the 4 p tecunumanii provenances were found to be very similar to that of the 3 controls used in the study but crown breaks were very common probably due to the tendency of p tecunumanii to develop heavy branch whorls. Tracheid lengths and the pattern of within-tree variation were found largely similar among the various groups of trees studied but in comparison with the controls the tracheid cells of p tecunumanii were markedly larger in cross-sectional diameter because of their thicker walls and larger lumen diameters. However differences in the proportion of cell-wall material among the groups of trees studied were small. At both sites the annual ring structure of the wood of p tecunumanii differed pronouncedly from that of the controls having a mean latewood percentage of only about half of that of p patula and about one-third of that of p taeda and p elliottii. In spite of the large relative proportion of earlywood characterising the wood of p tecunumanii it produces wood very similar in density to that of p patula and p taeda and slightly higher than that of p elliottii. This was found due mainly to the fact that the broad earlywood zones of the Pinus tecunumanii provenances were substantially more dense than those of the commercial controls while differences in latewood densities among the various groups considered were small and non-significant. Apart .