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

Abstract

To better understand the phenomenon of growth "stagnation" in high-density lodgepole pine (Pinuscontorta Dougl. ex Loud.), leaf area 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 m 2 (dominants in stands of low stocking) to 0.05 m 2 (suppressed trees in stands of high stocking). Leaf area indices ranged from 13.4 to 2.3 m 2 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 m 2 cm −2 . Intraring wood density profiles showed that ovendry density increased from 0.52 to 0.7 g cm −3 and the proportion of early wood 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.