TAILIEUCHUNG - Báo cáo lâm nghiệp: " Influence of repeated defoliations by insects on wood increment in common oak (Quercus robur L)"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế, đề tài:Influence of repeated defoliations by insects on wood increment in common oak (Quercus robur L). | Ann Sci For 1996 53 407-412 Elsevier INRA 407 Short note Influence of repeated defoliations by insects on wood increment in common oak Quercus roburL vv Rubtsov Institute of Forest Science Russian Academy of Sciences Uspenskoe Moscow Region 143030 Russia Received 6 September 1994 accepted 13 February 1996 Summary The dynamics of radial wood increments were analysed over a 30 year period in oak stands Quercus robuij of the forest-steppe zone in the Voronezh region eastern-central Russia . Relative losses in wood increment due to insect-caused defoliations of diverse extents and periodicity were quantitatively assessed. Such estimates were made for trees with early and late phenology as well as with respect to growth classes and to local forest types. The intensity of the responses of dominant and codominant trees were shown to vary in different forest types. No differences in increment losses were detected between early and late oaks after one to three moderate defoliations. A factor two variation was observed in the intensity of the responses depending on actual climate. In response to repeated defoliations the ratio latewood to earlywood was reduced by a factor 5-8 in a stand and even 20 in an individual tree. This suggests that insect defoliation severely affects oak growth. radial increment wood leaf feeders oaks growth I defoliation Resume Effets de defoliateurs sur la croissance de chênes Ouercus robur L . Les dyna-miques de croissance radiale ont été suivies sur une période de 30 ans sur des chênes pédonculés Quercus robur L de la steppe forestiere de la region de Voronezh Russie centre-orientale . Les pertes relatives de croissance radiale dues à des defoliations par des insectes ont été évaluées quan-titativement. Ces estimations ont concerné à la fois des chênes tardifs et précoces alnsi que differentes classes de dominance et divers types forestiers. L intensite des réponses d arbres dominants et codominants variait en fonction de la station. En revanche

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