Análise da formação dos anéis de crescimento anual das árvores ao longo dum ciclo de actividade cambial

Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de AgronomiaThe growing awareness concerning the influence of environmental factors on tree´s growth, particularly under the threat of climate changes, fostered the design of a new method to study cambial activity and xylogenesis along the growing season, under the influence of Mediterranean climate. Unlike the currently used methods, that extract samples from the stem, this method is based on the collection of twigs from the crown, with the purpose of overcoming the disadvantages associated to other methods, such as the impact on tree, the associated cost, the lack of simplicity and of applicability to softwood and hardwood species. The study includes ten hardwood and softwood species. After microtome sectioning and staining (safranin and astrablue) techniques, the sections were photographed and analyzed, aiming at monitoring the ring development and defining the period of cambial activity. The twigs revealed great differences in the radial growth, that might be associated to their particular position in the tree (proximity of leaves, source of photoassimilates) and/or to the effect of the different microclimates created in the crown. The method showed effectiveness in the study of cambial activity, revealing, however, limitations on the study of ring development, due to the impossibility to compare samples