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The light-penetration pattern for a mangrove Kandelia obovata canopy was analyzed considering the vertical changes in the light-extinction coefficients for leaves and woody organs. Furthermore, canopy photosynthesis and foliage respiration were estimated on the basis of the constructed light-penetration models. The canopy structure and light-penetration pattern were investigated by use of a destructive method. Seasonal changes in photosynthetic light-response curves and dark respiration of leaves were measured at different canopy depths. The main findings of this study were: (1) the ratio of the cumulative woody silhouette area density C to the cumulative leaf area density F increased downward within the canopy; (2) the light-extinction coefficient for leaves increased from 0.30 to 0.72 downward and the light-extinction coefficient for woody organs was almost constant at 0.77; and (3) ignoring the woody organs and the vertical change in the C/ F ratio and light-extinction coefficients for leaves caused ca. ±10 and ±20% errors in annual canopy gross photosynthesis and surplus production, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The hypothesis was tested that potential tree height and biomass in mangroves decrease downstream with the tidal gradient along the Okukubi River in Okinawa Island, Japan. The mangrove stands consisted of Bruguiera gymnorrhiza (L.) Lamk. and Kandelia obovata (S., L.) Yong (Rhizophoraceae). Four sites were selected considering the distance from the mouth of the river. Soil salinity increased downstream, while soil total nitrogen content decreased. The soil redox potential did not vary along the river. Maximum gross photosynthesis and tree height for each species decreased downstream. The potential tree height (H max) inferred from the stem diameter (D 0.1)–tree height (H) relationship ( a, h, coefficient) in each species decreased downstream. The tree density (ρ)–mean tree size () relationships ( K, α, coefficient) determined for four sites revealed that the mean tree size at any given tree density decreased downstream, which indicates the decrease of potential biomass. Furthermore, an index for biomass () was homogeneous within a site regardless of tree density, i.e. the value of α at each site did not differ significantly from 1.0 (p >0.05). The decreases in potential tree height and biomass may be partially ascribed to the stressful environments at the downstream sites characterized by high salinity (>2.6%) and nitrogen-poor soils (<0.25ppt) in our study area. [Copyright &y& Elsevier]