A COMPARISON OF DIRECT AND INDIRECT METHODS FOR MEASURING LEAF AND SURFACE-AREAS OF INDIVIDUAL BUSHES

Indirect estimates of leaf area from measurements with three commercia lly available instruments (DEMON, LAI-2000 and Sunfleck Ceptometer) we re compared with directly measured areas of individual Retama sphaeroc arpa bushes, The three indirect methods gave good estimates of the tot al surface area of individual bushes, For the DEMON, the method of log -linear averaging of transmitted radiation gave estimates closer to di rectly measured surface area than the method of averaging transmission Linearly. For the LAI-2000, estimated surface area index multiplied b y canopy projected area gave the best agreement with directly measured values. For measurements with the Sunfleck Ceptometer, values of surf ace area estimated from the transmission of photosynthetic quantum flu x density, without correcting for diffuse radiation, gave the best agr eement with directly measured values, Surface areas estimated by the t hree instruments were not significantly different from directly measur ed total (leaf + branch + stem) surface areas. Leaf surface area could be calculated from estimated total surface area minus directly measur ed branch surface area. Measured branch surface area was linearly rela ted to canopy projected area,