tailieunhanh - Báo cáo lâm nghiệp: "Summer and winter embolism in oak: impact on water relations"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế, đề tài:"Summer and winter embolism in oak: impact on water relations. | Ann Sci For 1996 53 173-180 Elsevier INRA 173 Review article Summer and winter embolism in oak impact on water relations MT Tyree 1 H Cochard 2 Aiken Forestry Sciences Laboratory USDA Forest Service PO Box 968 Burlington VT 05402 USA 2 Unite d ecophysiologie forestiere Inra 54280 Champenoux France Received 31 October 1994 accepted 21 June 1995 Summary In this paper we review vulnerability to embolism caused by drought and freezing in six species of oak Quercus . The xylem pressure potential that induces 50 loss hydraulic conductivity ranges from to MPa for the species reviewed and correlates with other measures of drought tolerance in oaks. The probability of vessel dysfunction increases with vessel size for both drought- and freezing-induced embolism. The impact of embolism is a reduction in hydraulic conductivity in the vascular system. We conclude that embolism plays little role in the drought tolerance of oaks since drought-induced embolism occurs at more negative water potentials than are known to cause damage eg reduced growth or mortality. Nevertheless vulnerability to embolisms probably explains species distributions between wet and dry sites or may explain the evolution of stomatai physiology. Oaks seem to operate close to the point of xylem dysfunction but oaks protect against embolism by stomatai regulation which keeps water potentials above that causing run-away embolism. In conclusion vulnerability to summer embolisms correlates with other measures of drought tolerance of oak species but significant summer embolisms are generally avoided. On the other hand frost-induced embolism may explain species distributions in cold climates. Quercus spp embolism water relations hydraulic conductance Resume Embolie estivale et hivernale Chez les chênes consequences sur les relations hydriques. Get article fait la synthèse des données sur la vulnérabilité à I embolie causée par stress hydrique et thermique de six espèces de chênes Quercus . Le potentiel .

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