INTERCEPTION OF PHOTOSYNTHETIC PHOTON FLUX-DENSITY BY WOODY ELEMENTS IN A HINOKI (CHAMAECYPARIS-OBTUSA (SIEB ET ZUCC) ENDL) STAND

A hinoki stand was divided into the following two layers: one was a le afed upper layer consisting of leaves and woody elements, such as stem s, living branches and dead branches; the other was a leafless layer c onsisted of woody elements, such as stems and dead branches. Photosynt hetic photon flux density (PPFD) penetrating through the stand was mea sured in relation to the silhouette area of leaves and woody elements. The silhouette area, on a ground area basis, was 11.2 ha ha(-1) for l eaves (leaf area index), 0.26 ha ha(-1) for stems, 0.40 ha ha(-1) for living branches and 0.69 ha ha(-1) for dead branches, yielding a total wood silhouette area of 1.35 ha ha(-1). The apparent extinction coeff icient, K, was computed to be 0.420 ha(-1) ha for the leafed layer, wh ile the extinction coefficient of woody elements, K-C, was computed to be 1.01 ha(-1) ha for the leafless layer. The cumulative wood silhoue tte area density from the top of the canopy down to a given depth incr eased with an increase in the corresponding leaf area density within t he leafed layer. The extinction coefficient of leaves, K-F, was estima ted to be 0.367 ha(-1) ha. Of the PPFD extinguished within the canopy, the fraction (K-F/K) due to leaves alone was evaluated to be 87.4%.