Leaf mass per area relationships across light gradients in hybrid spruce crowns

This study examined the distribution and variation of mass to projected area ratio of foliage (LMA, g/m(2)) within hybrid spruce (Picea engelmannii ParryxPicea glauca (Moench) VossxPicea sitchensis (Bong.) Carr) crowns across three stages of stand development (20, 60, and 140 years). Variability of LMA was assessed at different heights and branch positions. LMA decreased with distance from top of tree (p < 0.0001) at rates that varied among stand development stages (p < 0.0001). A multi-level mixed effect analysis indicated that distance from the tip of the first-order branch (p=0.0002) had a significant influence on LMA. In general, LMAs decreased towards the base of the tree and increased towards tree apex. LMA differed significantly across stand development stages. Older trees (140 years) showed the highest LMA, while younger trees (20 years) showed the lowest LMA values. LMA also increased with foliage age, suggesting a developmental change in leaf area and mass with increasing foliage age. Multiple linear regression (MLR) relationships were developed to predict LMA at various positions within tree crowns. The precision of the models was slightly greater when branch position (from the apex of the tree) was described relative to tree height, rather than relative to crown length. The MLR function resulted in precise representations of LMA within tree crowns.