Cambium phenology and dendrochronology of the endangered tropical tree Ocotea catharinensis Mez

Ocotea catharinensis occurs mainly in the Brazilian Atlantic Forest and is highly threatened by timber logging, forest fragmentation, and habitat loss. The remnant populations of this species are genetically rich, which may be related to the presence of long-lived trees, and so it is imperative to understand their growth and age. In this study, we analyzed trees of O. catharinensis from dense ombrophylous forest, its dendrochronological potential, the period of cambial activity and dormancy, and the influence of climate on annual growth. The species showed distinct annually-formed tree-rings, with cambial activity during summer and autumn, and cambial dormancy during winter and spring. A tree-ring width chronology was built from 1852–2015. The estimated age of the sampled trees varied from 40 to 164 years. O. catharinensis in our study site does not show a strong age–diameter relationship, hence similar diameters at breast height resulted in differences in ages by as much as 50 years. The resulting tree-ring width chronology is positively correlated with March precipitation, the transition month between rainy and dry seasons. This study brings valuable contributions to the understanding of the growth of O. catharinensis, which is a novelty for this species and important to the maintenance of these long-lived trees in natural forests.

FORMATION OF INCREMENT ZONES AND INTRAANNUAL GROWTH DYNAMICS IN THE XYLEM OF SWIETENIA MACROPHYLLA, CARAPA GUIANENSIS, AND CEDRELA ODORATA (MELIACEAE)

The pattern of growth increment zones, the cambial growth dynamics and the structural variation in wood formation of Swietenia macrophylla King, Carapa guianensis Aubl., and Cedrela odorata L. (Meliaceae) were investigated in order to understand the relationship of site conditions and sustainable growth in Central Amazonian plantations. Trees were available from 8-, 17-, 23-, and 57-year-old plantations, and from primary forests in Manaus (Amazônia), Santarem (Pará), and Aripuanã (Mato Grosso). The wood anatomical structure and the annual increments of 61 Swietenia, 94 Carapa, and 89 Cedrela trees were studied for different tree heights. The curves of annual increments were cross-dated and tested for synchronisation. The cambial growth dynamics of up to 52 trees per species were dated by means of dendrometer measurements, monthly labelling by pinmarkers, and extracted cambium samples investigated using a microscope. The intraannual course of the growth and structural variation was compared with the water supply of the soil and insect attacks (Hypsipyla grandella (Zeller) Lep.).In Swietenia and Carapa parenchyma and vessel bands as well as bands of resin canals were observed. Within the xylem of Cedrela, alternating bands of fibres and vessels surrounded by paratracheal parenchyma were found; bands of resin canals were only occasional. In the juvenile wood of Swietenia and Carapa no synchronization of the increment curves was possible, whereas the increment curves obtained in the juvenile wood of Cedrela showed parallel run in growth. The increment curves obtained in adult wood of Swietenia and Cedrela indicate an annual formation of increment zones, whereas the number of increment zones in the xylem of Carapa was approximately 50% higher than the tree age (years) indicating that the growth increments of Carapa also were not annual during the adult phase of growth.The study of the intraannual growth dynamics of the trees showed that the formation of parenchyma bands in Swietenia is induced by dry periods before a cambial dormancy. The formation of parenchyma bands of Carapa was induced by extremely dry and extremely wet periods before a cambial dormancy, whereas fibre bands in Cedrela were induced by dry periods before a cambial dormancy and the formation of vessel bands embedded in paratracheal parenchyma was induced by wet periods after a cambial dormancy. In addition, insect attack (Hypsipyla grandella) induced locally restricted formation of parenchyma bands and bands of resin canals in Swietenia, Carapa and Cedrela.

SEASONAL CAMBIAL ACTIVITY AND PHYTOGEOGRAPHIC ORIGIN OF WOODY PLANTS: A HYPOTHESIS

An attempt was made to examine the hypothesis that the annual course of cambial activity is a permanent feature of each woody plant, related to its phytogeographic origin. Existing data on cambial activity in woody plants growing in Israel have been presented in a comprehensive diagram which shows a correlation between the course of activity and the phytogeographic origin of the various plants. Some attempts to prevent the occurrence of a period of cambial dormancy in plants which normally have such a period were unsuccessful.

Histochemistry of the dormant vascular cambium of Abies balsamea: changes associated with tree age and crown position

On three dates during September–December, the histochemistry and dormancy status of cambial zone cells were investigated in 6- and 19-year-old balsam fir (Abies balsamea) trees at the top of the crown (1-year-old cambium) and near the base of the bole (5- and 13-year-old cambium, respectively). The extent of dormancy on the date of collection and after 4 weeks in controlled-environment conditions favorable for growth indicated that a changeover between the dormancy stages of rest and quiescence occurred in all ages of the cambium during the experimental period. In trees of both ages, cambial dormancy began later, and the number of fusiform cells in the cambial zone was greater at the bottom of the tree than at the top. The staining intensities for total cytoplasmic RNA, protein, and insoluble carbohydrates in the fusiform cambial zone cells increased during the rest–quiescence transition at the top and bottom of the 6-year-old trees and at the top of the 19-year-old trees. However, no significant increase in RNA staining occurred at the bottom of the 19-year-old trees.