• Detection of Atypical Years in the Tree-Ring Series by Construction of a Temporal Walk in the Principal Components Planes

      Dutilleul, Pierre; Till, Claudine; Unité de Biométrie et Analyse des Données, Faculté des Sciences Agronomiques, Université Catholique de Louvain, Louvain-la-Neuve, Belgium; Rue des Blancs Chevaux 1/404, B -1348 Louvain-la-Neuve, Belgium (Tree-Ring Society, 1989)
      The purpose of this paper is to introduce a method for identifying years of anomalous radial growth, which are called atypical years and are characterized by particularly narrow rings for certain trees or sites, and wide for the others. With this aim, we use principal components analysis (PCA) of tree -ring series, where years are the variables and trees or sites are the individuals, even though in classical dendrochronological applications of PCA, the trees or sites are considered as variables and the years as cases. The relevant method is explained and results are given for five cedar forests (Cedrus atlantica (Endl.) Carrière) in Morocco.
    • Preserving Decayed Wood Samples for Tree-Ring Measurement

      Krusic, Paul J.; Hornbeck, James W.; USDA Forest Service, Forest Experiment Station, Radnor, PA, Durham, NH (Tree-Ring Society, 1989)
      Wood disks in various states of decay can be inexpensively preserved and prepared for accurate crossdating and precise tree-ring measurement by impregnation with commercial wood glue. The technique does not affect the dimensions or physiological features of samples preserved in this manner. Dead red spruce trees on Mt. Washington, New Hampshire, remain available for dendrochronological examination as long as 29 years after their last year of stem growth.
    • Dendroclimatological Study of Pinus Sylvestris L. in Southern Catalonia (Spain)

      Gutiérrez, Emilia; Departamento d'Ecologia, Facultat de Biologia, Universitat de Barcelona, Barcelona (Tree-Ring Society, 1989)
      Two modem tree-ring width chronologies of Pinus sylvestris L. have been established in an area near the southern limit of the species' distribution. Trees were sampled in the South of Catalonia in northeastern Spain where Mediterranean climatic conditions are of primary influence. To better understand climate ring-width relationships, tree-ring index series have been studied in relation to local climate. Ring-widths are strongly related to low precipitation at the beginning of the growing season in March, in June of the current growth year, and in September prior to tree-ring growth. High temperatures mainly affect growth in summer during the growing season and in autumn of the year prior to growth. During the winter, mainly in December, mean monthly temperatures show a significant positive correlation with growth. Major factors controlling the southern distribution of P. sylvestris may be related not only to water stress in summer but also to the amount of precipitation at the beginning of the growing season and in autumn, even in mild winters.