Two-dimensional needle-area density distribution within the crowns of Pinus radiata

The vertical and horizontal distribution of needle-area density (NAD) within the crowns of Pinus radiata trees is described with a two-dimensional beta function. The maximum NAD for the entire needle population within the tree crowns was located approximately one-third of tree-crown length from the crown base in the vertical and half-way along the crown radius at that height in the horizontal. The relative heights of maximum NAD of needles in different age classes decrease with needle age in the vertical, whilst the relative radial distances of maximum NAD of needles in different age classes are close to the centre of the tree crown in the horizontal. It was found that the maximum NAD within the tree crown can be up to four times larger than the average NAD. The spatial NAD distribution was poorly related to trunk diameter at breast height, tree height, and the total area of needles within the crown.