A model of seasonal foliage dynamics of the subtropical mangrove species Rhizophora stylosa Griff.growing at the northern limit of its distribution

Background： Progress of forest production in response to the environment requires a quantitative understanding of leaf area development. Therefore, it is necessary to investigate the dynamics of seasonal crown foliage in order to understand the productivity of mangroves, which play an important role in the subtropical and tropical coastlines of the world. Method： Crown foliage dynamics of the mangrove Rhizophora styloso were studies to reveal patterns of leaf recruitment, survival and seasonal leaf area growth. Results： Flushing of leaves occurred throughout the year, but both flushing and leaf area growth pattern of leaves varied with season. Maximum flushing occurred in summer, but leaf areas did not differ significantly with season. The half-expansion period is longer, and the intrinsic rate of increase was lower in winter. Summer flushed leaves grew faster at their initial stage and reached their maximum area over a shorter period of time. The difference in temperature and air vapor pressure deficit （VPD） between summer and winter contributed to the present dynamics of foliage patterns. The mean leaf longevity was estimated to be 13.1 month. The crown foliage area was almost stable throughout the year. Conclusions： Homeostatic control of the crown foliage area may be accompanied by the existence of ecophysiological mechanisms in R. stylosa. Integrating crown foliage dynamics into forest models represents an important step towards incorporating physiological mechanisms into the models for predicting growth responses to environmental changes and for understanding the complex responses of tree growth and litter production.     

Trends in allometric models and aboveground biomass of family Rhizophoraceae mangroves in the Coral Triangle ecoregion,Southeast Sulawesi,Indonesia

This study aims to establish allometric models and estimate aboveground biomass (AGB) of mangroves Rhizophoraceae in the Southeast Sulawesi, Indonesia. Allometric models of the AGB of mangroves Rhizophora apiculata, R. mucronata, and Ceriops tagal were established using independent variables consisting stem diameter at 30 cm from the ground (D₃₀), diameter at breast height (DBH), D₃₀²H and DBH²H. The AGB of mangroves was estimated by applying allometric model and tree census. The results showed that the best fitting allometric models of AGB for R. apiculata is based on variable DBH, while DBH²H is the best variable for R. mucronata trees. Conversely, the D₃₀ is the best variable for estimating AGB of C. tagal trees. Thus, there is some variation of independent variables on allometric models for the estimation of AGB for Rhizophoraceae mangroves. The AGB (ton ha^?1) of R. apiculata, R. mucronata, and C. tagal was estimated respective 651.60, 232.11 and 154.56 in the protected area, and respective 137.59, 189.35 and 39.06 ton ha^?1 in the unprotected area. Higher AGB of mangroves growing in the protected area indicated the suitable condition and undisturbed by human activities. The conservation of mangroves is necessary for the sustainability of mangroves and coastal ecosystems in the Coral Triangle ecoregion.