Seasonal changes in canopy photosynthesis and foliage respiration in a Rhizophora stylosa stand at the northern limit of its natural distribution
2008
Suwa, Rempei | Hagihara, Akio
Gross photosynthesis and respiration rates of leaves at different canopy heights in a Rhizophora stylosa Griff. stand were measured monthly over 1 year at Manko Wetland, Okinawa Island, Japan, which is the northern limit of its distribution. The light-saturated net photosynthesis rate for the leaves at the top of the canopy showed a maximum value of 17 μmol CO₂ m⁻² s⁻¹ in warm season and a minimum value of 6 μmol CO₂ m⁻² s⁻¹ in cold season. The light-saturated gross photosynthesis and dark respiration rates of the leaves existing at the top of the canopy were 2-7 times and 3-16 times, respectively, those of leaves at the bottom of the canopy throughout the year. The light compensation point of leaves showed maximum and minimum peaks in warm season and cold season, respectively. The annual canopy gross photosynthesis, foliage respiration, and surplus production were estimated as 117, 49, and 68 t CO₂ ha⁻¹ year⁻¹, respectively. The energy efficiency of the annual canopy gross photosynthesis was 2.5%. The gross primary production GPP fell near the regression curve of GPP on the product of leaf area index and warmth index, the regression curve which was established for forests in the Western Pacific with humid climates.
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