Interception of photosynthetic photon flux density in a mangrove stand of <Emphasis Type="Italic">Kandelia candel</Emphasis> (L.) Druce

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 © and leaf area (F) densities from the top down to a given depth of the canopy, C = aF (r ² = 0.950), with a proportional constant a of 0.096 ± 0.008 (mean ± SE). The PPFD relative to that above the canopy (relative PPFD; I _R) at a given depth of the canopy was assumed to be given by the equation I _R = e^–(KCC+KFF ) = e^–KF , where the apparent light extinction coefficient K (= K _F + aK _C , where K _F and K _C are respectively the light extinction coefficient of leaves and woody organs) was calculated to be 0.502 ± 0.041 (mean ± SE) m^–2m² before leaf clipping. After leaf clipping, I _RC = e^–KCC is satisfied. As a result, the value of K _C was estimated to be 0.785 ± 0.046 (mean ± SE) m^–2m². The light extinction coefficient of leaves K _F was calculated to be 0.427m^–2m² using the indirect method, K _F = K – aK _C, and 0.432 ± 0.026 (mean ± SE) m^–2m² using the direct method, I _R/I _RC = e^–KFF . Of the total PPFD intercepted by the canopy, the fraction K _F/K due to leaves alone was estimated to be 85.0%–86.1% and the rest was contributed by woody organs.