WOOD ANATOMICAL VARIABLES IN TROPICAL TREES AND THEIR RELATION TO SITE CONDITIONS AND INDIVIDUAL TREE MORPHOLOGY

For a better understanding of the influence of external growth factors on the wood structure, samples of 139 tropical trees were analysed across plant families and a wide climatic gradient. For all samples a unique data set on climate, site and forest stand conditions is available. Different vessel variables as well as the relative cross-sectional area of vessel, parenchyma and fibre tissue were studied in individual tree rings of varying sizes. High within-species and within-site variation of wood anatomical variables was observed which was higher than inter-species and -site variation. In addition, between-ring variation within many individuals was higher than variation between individuals. The differences within individuals show how trees can adapt or adjust to environmental variability and can provide information about the plasticity of a species under changing environmental conditions. The variable 'vessel diameter' showed the strongest and most significant correlations to other wood anatomical variables, but also to climate parameters and tree morphology. Thereby tree size (DBH & height) and crown exposure to light had the strongest impact on vessel size and consequently on hydraulic stem architecture. General climate conditions only showed a weak influence on vessel variables. The principal component analyses revealed a strong influence of tree morphology and a weaker influence of climate on the hydraulic stem architecture. In contrast the general climatic site conditions strongly influenced fibre and parenchyma tissue.