Abstract
This study investigated effects of differences of the processes of direct measurements of leaf area index (LAI) and their combinations on the estimation of LAI for planted stands of Japanese cedar (Cryptomeria japonica D. Don). The processes consist of selection of sample tree(s), sampling of leaves, and planimetry of leaf area. Each process has several methods, therefore, estimated LAI will have variations. As for a selection of sample tree(s), estimated LAI was smaller than 10% when a sample tree was only one, in comparison with selecting three sample trees. In this case, the possibility of underestimating LAI is implied when only one sample tree is selected in the stand which represents the average basal area. As for sampling of leaves, the estimated LAI was 10% larger than that by the clipping method, when 1% of the total leaves were selected for the planimetry to consider the labor efficiency. As for planimetry of leaf area, empirical equations between specific leaf area (SLA) and the diameters of leaves were used. In this process, the difference of estimated LAI was within 5% when the sampled leaves were classified to pre-determined classes of the diameters of leaves, in comparison with the usage of averaged diameter of the leaves. Although the differences of estimated LAI in each process was not so large, the accumulation of these differences led to as large as 40% of estimated LAI, even in the planted stands of Japanese ceder which were taken care of such as pruning or thinning.
