tailieunhanh - Báo cáo toán học: "Impact of late frost on height growth in young sessile oak regeneration"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: Impact of late frost on height growth in young sessile oak regenerations. | 417 Ann. For. Sci. 56 1999 417-429 Inra Elsevier Paris Original article Impact of late frost on height growth in young sessile oak regenerations Hatem Chaar Francis Colin Unite de recherche croissance Production et qualité des bois Institut national de la recherche agronomique Centre de Nancy 54280 Champenoux France Received 21 April 1998 accepted 16 June 1998 Abstract - The damage due to late frost during the 1995 and 1996 growing seasons was analysed in sessile oak seedlings in a natural regeneration. The seedlings were 5 years old at the beginning of the 1995 growing season. In 1995 frost occurred after the complete elongation of the growth unit GU of the stem which was produced during the first period of elongation. In 1996 frost occurred during the elongation period of the first GU. Damage intensity was observed visually and ranged from simple necroses of the leaf or the terminal bud of the new GU to the total loss of the GU. Damage intensity appeared to depend on the growing season and the bud phonological stage when frost occurred but not on the initial dimensions height and collar diameter of the seedling. Damage was higher when the seedling was at the shoot elongation stage 1996 growing season and lower when the seedling was in apparent rest 1995 growing season . The consequences of frost damage on growth were greater in the 1996 growing season. The bud resting period after the first period of elongation and before regrowth was shorter in 1996. Regrowth occurred from either a bud from the damaged GU or a bud from the GU grown during the previous growing season. In the latter case the GU was sometimes longer than the GU from an axillary bud of the damaged GU. The second elongation period was shorter in 1996 than in 1995 and led to a relatively small GU. The intensity of frost damage which had an effect on the length of the GUs produced during the second period of elongation had no subsequent effect on the length of those produced during the third elongation