Mesostructure Elastic Properties in Loblolly Pine

An obvious visual feature of wood structure in many coniferous species, and especially pines, is the presence of annual growth rings. The growth rings are not completely uniform in width and often provide a record of weather and climate-based events that had an impact on growth. These events have impacts on the formation of the tapered cylindrical layer of earlywood in the early part of the growing season followed by the formation of the layer of latewood in the latter part of the growing season (Larson 1969). Cell diameter and secondary wall thickness are the main characteristics distinguishing earlywood from latewood. However these two characteristics can be altered independently by different factors. Although there is a general understanding of the difference between earlywood and latewood, there is not a definition of latewood tracheids that satisfies all conditions. Silvaculture practices impact the growth process including the formation of earlywood and latewood. The move to managed tree plantations has generally resulted in wider rings with greater proportions of earlywood, expected outcomes from strategies that include thinning, pruning and fertilization. The earlywood and latewood bands represent the mesostructure of wood. The microstructure is made up of individual cells and the typical macrostructure assumptions ignore the growth rings where wood is assumed to be a homogeneous, orthotropic continuum.