The characteristic pattern of stand growth, which peaks at about the age of canopy closure, reflects the fact that stand growth depends on both the amount and efficiency of leaf area. Leaf area of lodgepole pine stands begins to decline following canopy closure and part of this decline appears to result from increasing inter-crown abrasion as trees become taller. Concomitant with the decline in stand leaf area is a reduction in relative foliar efficiency as a lower proportion of aboveground biomass is allocated to foliage. The combination of these two factors, reduced amount and efficiency of leaf area, is associated with the progressive decline in stemwood production in aging lodgepole pine stands. As stands age, foliage represents a decreasing proportion of total aboveground biomass.
Large crowns are less efficient at producing stemwood than are small crowns.
From Long, J.N. and F.W. Smith. Volume increment in Pinus contorta var. Smith, F.W. and J.N. Long. 1989. The influence of canopy structure on stemwood production and growth efficiency of Pinus contorta var. latifolia.