When a single equation was used to predict leaf area under all growth conditions

Estimation of leaf area with an integrating sphere

Recently ,there goes the saying of estimation of leaf area with an integrating sphere,the article will give a detailed introduction for this estimation saying. Please read the following sentences carefully ,and hope you can get something from them.Relative absorptance of intact branches measured with integrating sphere was compared to leaf area estimated by the commonly used methods (volume displacement and scanning area meter) for three conifer species:Picea mariana (Mill.) BSP, Pinus banksiana (Lamb.) and Pseudotsuga menziesii (Mirb.) Franco. A consistent relationship between relative absorptance and surface area came out for the three species. The ability to predict leaf area from absorptance was further explored by measuring branches of Pseudotsuga menziesii grown in varying light and nutrient regimes. When a single equation was used to predict leaf area under all growth conditions, errors were as large as 40% primarily because of variation in leaf absorptivity, with the largest errors associated with extremely nutrient-deficient foliage. When separate empirical equations were developed for each growth treatment, predicted leaf surface area agreed to within 5% of the area determined by the volume displacement method. Leaf surface area estimated from theoretical principles was also in good agreement with total surface area estimated independently by conventional methods. With proper accounting for needle absorptivity, which varied with growth conditions, leaf area estimates obtained by the integrating sphere method were of similar accuracy to those obtained by conventional methods, with the added advantage that the method allowed intact foliage to be sampled nondestructively in the field. Because the integrating sphere method protects branch structure in the process of measurement, it could provide a useful measurement of needle area for photosynthetic or developmental studies requiring repeated sampling of the same branch.