TOTAL LEAF AREAS OF SINGLE TREES OF EUCALYPTUS-GRANDIS ESTIMATED FROM TRANSMITTANCES OF THE SUNS BEAM

Total leaf areas of isolated plants can be estimated from the transmittance of the direct beam of the sun. Leaf area is obtained by integrating the logarithm of transmittances over an area which encompasses the shadow of a plant. Details of the theory and procedures are given. A central assumption of the method is that projections of the foliage are arranged randomly on an area about 10 times the area of leaves. Experiments with small trees grown in the field and in pots showed that total leaf areas for E. grandis trees estimated from transmittances were linearly correlated with measurements from a planimeter, over a range of leaf areas from 0.06-1.6 m2 per tree, and were, on average, 14% lower. The lower values were probably caused by departures from the random distribution which was assumed theoretically. Because of its operational simplicity, acceptable accuracy and theoretical basis, the procedure is believed to be useful for studies of developing trees in plantations in the early stages of growth, for ecological studies in sparsely vegetated communities, and for estimates of surface area when examining spray retention and rainfall interception by isolated plants.