Photosynthetic Yield Model And The Response To Environmental Factors For 5 Kinds Of Mangroves

The photosynthetic yield models of photosynthesis were established at the level of leaves and the canopies of Bruguiera gymnorriza and Avicennia marina, Aegiceras corniculata, Kandelia candel and Excoecaria agallocha. The quantitative relations between photosynthetic yield at levels of leaves, individual and population and environmental factors were analyzed.A coupled model of photosynthesis was given by means of combining biochemical model of photosynthesis introduced by Farquhar with B-B model of stomatal conductance. The estimated results by this coupling model were consistent with the measured data. When PAR maintains 1000μmol·m^-2s^-1and CO2 concentration in the atmosphere doubles (from 360 to 720μmol·mol^-1), the leaf photosynthetic rate of A. marina, B. gmnorriza, A. corniculatum, K. candel, E. agallocha respectively increases by 22.56%, 17.13%, 18.43%, 18.63% and 18.41%. The response of the photosynthetic rate to temperature is a one-humped curve, and the optimal temperature is about 26.5℃for all the 5 kinds of mangroves, when CO2 concentration in the atmosphere is at 350μmol·mol^-1 and PAR at 1000μmol·m^-2s^-1. The response of their photosynthetic rate to PAR is consistent with Michaelis-Menten's curve when CO2 concentration and temperature in the atmosphere keep constant (350μmol·mol^-1 and 25.0℃), and the simulation is reasonable when PAR is below 1800μmol·m^-2s^-1(P<0.01). In typical clear days, the diurnal course of the photosynthetic rate for the 5 kinds of mangroves presents a double-humped curve, which has two maximums at about 11:00 and 15:00; about at noon, their photosynthetic rate is depressed, the simulated diurnal course trend is consistent with the measured rate. The model appears to work well and be useful for the simulation of photosynthetic yield of the 5 kinds of mangroves and the response to environmental factors(P<0.01).On the basis of Ross's and Nilson's models of leaf declination distribution, the transmissive sub-models of direct and diffused radiation in the canopies were given according to their qualities and transmissive characteristics. The extinction coefficients in the canopies varied obviously daily, especially before 8:00 or after 16:00. In typical clear days, the daily total photosynthesized dry mass per unit area for B. gmnorriza, A. marina, A. corniculatum, K. candel, E. agallocha is respectively 22.254g·m^-2d^-1, 15.840g·m^-2d^-1, 23.610g·m^-2d^-1, 24.525g·m^-2d^-1 and 25.996g·m^-2d^-1 .