Cambial Age Research Articles

Dendroclimatology and dendroecology

Dendrochronology is the science of dating annual growth layers (rings) in woody plants. Two related subdisciplines are dendroclimatology and dendroecology. The former uses the information in dated rings to study problems of present and past climates, while the latter deals with changes in the local environment rather than regional climate. Successful applications of dendroclimatology and dendroecology depend upon careful stratification. Ring-width samples are selected from trees on limiting sites, where widths of growth layers vary greatly from one year to the next (sensitivity) and autocorrelation of the widths is not high. Rings also must be cross-dated and sufficiently replicated to provide precise dating. This selection and dating assures that the climatic information common to all trees, which is analogous to the “signal”, is large and properly placed in time. The random error or nonclimatic variations in growth, among trees, is analogous to “noise” and is reduced when ring-width indices are averaged for many trees. Some basic facts about the growth are presented along with a discussion of important physiological processes operating throughout the roots, stems, and leaves. Certain gradients associated with tree height, cambial age, and physiological activity control the size of the growth layers as they vary throughout the tree. These biological gradients interact with environmental variables and complicate the task of modeling the relationships linking growth with environment. Biological models are described for the relationships between variations in ring widths from conifers on arid sites, and variations in temperature and precpitation. These climatic factors may influence the tree at any time in the year. Conditions preceding the growing season sometimes have a greater influence on ring width than conditions during the growing season, and the relative effects of these factors on growth vary with latitude, altitude, and differences in factors of the site. The effects of some climatic factors on growth are negligible during certain times of the year, but important at other times. Climatic factors are sometimes directly related to growth and at other times are inversely related to growth. Statistical methods are described for ascertaining these differences in the climatic response of trees from different sites. A practical example is given of a tree-ring study and the mechanics are described for stratification and selection of tree-ring materials, for laboratory preparation, for cross-dating, and for computer processing. Several methods for calibration of the ring-width data with climatic variation are described. The most recent is multivariate analysis, which allows simultaneous calibration of a variety of tree-ring data representing different sites with a number of variables of climate. Several examples of applications of tree-ring analysis to problems of environment and climate are described. One is a specification from tree rings of anomalies in atmosphere circulation for a portion of the Northern Hemisphere since 1700 A.D. Another example treats and specifies past conditions in terms of conditional probabilities. Other methods of comparing present climate with past climate are described along with new developments in reconstructing past hydrologic conditions from tree rings. Tree-ring studies will be applied in the future to problems of temperate and mesic environments, and to problems of physiological, genetic, and anatomical variations within and among trees. New developments in the use of X-ray techniques will facilitate the measurement and study of cell size and cell density. Tree rings are an important source of information on productivity and dry-matter accumulation at various sites. Some tree-ring studies will deal with environmental pollution. Statistical developments will improve estimation of certain past anomalies in weather factors and the reconstructtion of atmosphere circulation associated with climate variability and change. Such information should improve chances for measuring and assessing the possibility of inadvertent modification of climate by man.

Ulteriori Osservazioni Sulla Variabilità Del Legno Secondario inPrunus PersicaStokes

Abstract Further observations on the variability of the secondary wood of PRUNUS PERSICA Stokes. — The length of both fibres and vessel members and the age of cambium in the trunk of a wild specimen of Prunus persica are positively correlated; no relation exists between the length of the above mentioned elements and the width of growth layers. The relation between the intrasive growth of fibres and either age of cambium or width of growth layers has been also calculated but no significant relation has been attained. The results have been compared with those obtained in the previous study of a trunk of a grafted Prunus persica, which are very different and quite peculiar mainly as to a decrease in length of fibres and vessel members with aging of cambium. The growing practice to which the tree may have been subjected is regarded as the possible cause of this peculiarity.

VERTICAL RESIN DUCTS IN THE SECONDARY WOOD OF THE ABIETINEAE

PAGE Introduction II Origin of the resin ducts and associated tissue 2I Character of the tissue associated with the ducts I4 Character and distribution of ducts at wounds . 2I The distribution of ducts and its interpretation 28 Phylogenetic considerations . 32 Comparison of the responses to wounding in the seedling and the adult 34 Relation between the response to wounding and cambial age 37 Comparison of the responses to wounding in different genera 40 Phylogenetic interpretations and fossil evidence 42 Summary 44 References 45