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.
