Foliage biomass and specific leaf area equations at the branch, annual shoot and whole-tree levels for lodgepole pine and white spruce in British Columbia

The distribution and characteristics of foliage are important aspects of tree structure and have implications for the productivity of individual trees and whole stands. We modelled foliage biomass and specific leaf area (SLA) using a sample of 60 lodgepole pine (Pinus contorta) and 60 white spruce (Picea glauca) that were destructively sampled in British Columbia, Canada. We modelled foliage biomass and SLA at three scales of organization: individual primary branches, annual shoots (all branches on an annual increment of the main stem), and the whole tree. We used a variety of independent variables that range in scale from the branch to plot level. Models of foliage biomass and SLA differ substantially between the two species even though their basic architectural design is quite similar. Models differed notably among levels of organization. For branch-level biomass, relevant variables for both species included branch diameter, length, age, distance to the crown base, and a measure of crown contact; however, at the annual-shoot level, relevant explanatory variables were mostly different between the species. At the whole tree-level, only crown length was common to both species and all other explanatory variables differed. SLA was higher in spruce than pine for all age classes and canopy positions. Overall, the models allow prediction of important crown properties for two major conifers at a range of scales, and can thus contribute to better prediction of stand growth and other properties.