Specific leaf area and leaf area index distribution in a young Douglas-fir plantation.

The spatial distribution of specific leaf area and leaf area index of needles in different age classes has been investigated in a young and unthinned Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) plantation in Central Italy through the destructive analysis of 12 trees sampled in four diameter size classes. Specific leaf area decreased with leaf age and from crown base to apex. A clear interaction between the effects of age and position on specific leaf area was demonstrated. For the whole canopy the vertical distribution of leaf area was well fitted by a normal curve equation, which explained 97% of the variation. The midpoint of the leaf area distribution, estimated as a parameter of the normal curve, was found to be 1.2 m below the mean canopy depth. The standard deviation of leaf area with respect to height was 16.4%. The midpoint of leaf area distribution decreased as leaf age increased and increased as diameter size class increased. Strong and significant linear relationships were found between leaf biomass, leaf area, sapwood area, and diameter at breast height.