Nicholas Davies edited intro.tex  over 7 years ago

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\section{Introduction}  Trees are subjected to multiple environmental mechanical loads and adapt the mechanical properties of their stems to an environment changing over time. Wind is one of the most important ---(Timell, 1986a)--. \citep{timell_compression_1986-2}.  Wind loading can cause mechanical failure making the tree worthless in a commercial sense. A substantial amount of research on predicting wind throw and wind damage risk for commercial species has been conducted --(Ancelin et al., 2004; Peltola et al., 1999; Mayer et al., 1989; Gardiner et al., 2000; Dunham and Cameron, 2000)---. \citep{ancelin_development_2004, peltola_mechanistic_1999, mayer_windthrow_1989, gardiner_comparison_2000, dunham_crown_2000}.  These models do not investigate the structural failure within the tree, but attempt to identify how likely failure is to occur in a particular environment. Wind also has less obvious effects. Continued wind loadings from a prevailing direction can cause reaction wood production in order to compensate for this loading --(Timell, 1986a)--. \citep{timell_compression_1986-2}.  While MicroFibril Angle (MFA) contributes to the stiffness of the cell wall, basic density measures the amount of cell wall in the tissue. Therefore overall mechanical wood properties rely on both features. Wood properties within 'normal' stems tend to follow what is known as the Typical Radial Pattern (TRP) \citep{meinzer_frederick_2011}. MFA reduces while density increases from the pith to the periphery of the stem. Note that this is not universal and some species and individuals do not necessarily follow the pattern completely.