CONVERSION OF TOTAL LEAF-AREA TO PROJECTED LEAF-AREA IN LODGEPOLE PINE AND DOUGLAS-FIR

Three definitions of leaf area index (LAI) in the literature have no p redictable relationship with each other. Factors were derived for conv erting total LAI to projected LAI of horizontal leaves and to projecte d LAI for inclined leaves of lodgepole pine (Pinus contorta Dougl. var . latifolia Engelm.) and coastal Douglas-fir (Pseudotsuga menziesii (M irb.) France) to allow comparison of results from different studies. A n algorithm was derived to allow determination of these factors based on twig angles and the angles that the foliage subtends with the twig. Allowances were made for both the vertical and horizontal components of projection. The value of the factor for converting total LAI to pro jected LAI for inclined leaves was 0.229 + 0.0032 for lodgepole pine a nd 0.230 + 0.0037 for Douglas-fir. Sensitivity analysis established th at this conversion factor was more sensitive to differences in vertica l angles of the twigs than to twig rotation or foliar arrangement on t he twig.