Interception of photosynthetic photon flux density by woody elements in a hinoki (Chamaecyparis obtusa [Sieb. et Zucc.] Endl.) stand

Abstract

A hinoki stand was divided into the following two layers: one was a leafed upper layer consisting of leaves and woody elements, such as stems, living branches and dead branches; the other was a leafless layer consisted of woody elements, such as stems and dead branches. Photosynthetic photon flux density (PPFD) penetrating through the stand was measured 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 leaves (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 coefficient,K, was computed to be 0.420 ha⁻¹ ha for the leafed layer, while the extinction coefficient of woody elements,K _c, was computed to be 1.01 ha⁻¹ ha for the leafless layer. The cumulative wood silhouette area density from the top of the canopy down to a given depth increased with an increase in the corresponding leaf area density within the leafed layer. The extinction coefficient of leaves,K _F, was estimated 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%.