Interception of photosynthetic photon flux density in a mangrove stand of Kandelia candel (L.) Druce

Abstract

The canopy structure and interception of photosynthetic photon flux density (PPFD) in a 10-year-old Kandelia candel (L.) Druce stand were investigated before and after artificial defoliation. Leaf and wood areas for different layers were measured through area-weight relationships of subsamples. PPFD was measured at specified heights before and after leaf clipping. The leaf area index (LAI) and wood area index (WAI) were 4.501m2m−2 and 1.412m2m−2, respectively. There was a strong linear relationship between the cumulative wood area (C) and leaf area (F) densities from the top down to a given depth of the canopy, C = aF (r2 = 0.950), with a proportional constant a of 0.096 ± 0.008 (mean ± SE). The PPFD relative to that above the canopy (relative PPFD; IR) at a given depth of the canopy was assumed to be given by the equation IR = e−(KCC+KFF) = e−KF, where the apparent light extinction coefficient K (= KF + aKC, where KF and KC are respectively the light extinction coefficient of leaves and woody organs) was calculated to be 0.502 ± 0.041 (mean ± SE) m−2 m2 before leaf clipping. After leaf clipping, is satisfied. As a result, the value of KC was estimated to be 0.785 ± 0.046 (mean ± SE) m−2 m2. The light extinction coefficient of leaves KF was calculated to be 0.427 m−2 m2 using the indirect method, KF = K − aKC, and 0.432 ± 0.026 (mean ± SE) m−2 m2 using the direct method, . Of the total PPFD intercepted by the canopy, the fraction KF/K due to leaves alone was estimated to be 85.0%–86.1% and the rest was contributed by woody organs.