Leaf area – sapwood cross-sectional area relationships in repressed stands of lodgepole pine

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Abstract
To better understand the phenomenon of growth "stagnation" in high-density lodgepole pine (Pinus contorta Dougl. ex Loud.), leaf are and its relationship with sapwood cross-sectional area were examined on both an individual tree and stand basis. Leaf areas of individual trees in a 22-year-old stand varied from 30.8 m2 (dominants in stands of low stocking) to 0.05 m2 (suppressed trees in stands of high stocking). Leaf area indices ranged from 13.4 to 2.3 m2 m-2 between low and high stocking levels, respectively. Over the same stocking range, the ratio of leaf area to sapwood cross-sectional area was reduced from 0.3 to 0.15 m2 cm-1. Intraring wood density profiles showed that ovendry density increased from 0.52 to 0.7 g cm-3 and the proportion of earlywood decreased over a stocking level range of 6500-109,000 trees/ha. A reduction in hydraulic conductivity in the stems of stagnant trees, suggested by the greater proportion of narrow-diameter tracheids present, may lead to a greater resistance to water transport within the boles of trees from stagnant stands, leading to low leaf areas.