Measuring and modelling stem growth and wood formation: An overview

Abstract

The immediate environment of a cambial initial (weather and nutritional factors, growth regulators, physical stresses) varies continuously over time. Consequently local conditions in the cambium influencing wood formation at any given instant are unique. The distribution of these conditions can be influenced by longitudinal gradients (stem base to apex), circumferentially or by local factors, such as proximity to branches. Not surprisingly, therefore, the variation in wood properties within a stem is large and in seasonal climates, the greatest variation is typically found within an annual ring. A great advantage for the study of wood is that the net product of seasonal processes is recorded in the wood structure across the stem radius. Thus by studying the pattern of wood property variation, within the context of its growth history, we can gain insight into cause and effect relationships between the drivers of wood variability. Combining this with temporal, high-resolution measurements of stem growth, weather, and process modelling enables us to better understand and test hypotheses of wood formation and the causes of variability in wood properties. Over recent years and in partnership with industry and other research providers, we have been attempting to model tree growth (Cabala) and cambial activity (TreeRing and CAMBIUM) at a daily time step to explain radial variability in wood properties. CAMBIUM is the latest development of this effort, modelling a population of eucalypt cambial cells, accounting for fibre and vessel formation using physiologically meaningful relationships.