五种红树植物光合产量模型及对环境因子的响应

以木榄（Bruguiera gymnorriza）、白骨壤（Avicennia marina）、桐花树（Aegiceras corniculata）、秋茄（Kandelia candel）和海漆（Excoecaria agallocha）为对象，以光合作用对环境因子的响应为主线，建立了从叶片水平到群体冠层水平上的光合产量模型，探讨了从器官、个体到群体的光合产量对环境因子响应的定量关系。 将Farquhar提出的单叶片光合作用生理生化模型与气孔导度B-B模型相结合，建立了光合作用－气孔导度耦合模型。模型模拟结果与实际测量结果具有较好的一致性。在温度为25.0℃，光合有效辐射为1000μmol•m-2s-1 的条件下，当外部CO2浓度倍增到720μmol•mol-1时，白骨壤、木榄、桐花树、秋茄、海漆的光合速率分别提高22.56%，17.13%，18.43%，18.63%和18.41%。在大气CO2浓度和光合有效辐射通量密度不变的条件下，光合作用速率对温度的响应呈单峰型曲线，即有一个最适温度，5种红树植物的最适温度值均为26.5℃左右。大气CO2浓度和温度固定不变（分别为350μmol•mol-1和25.0 ℃）时，光合作用对光合有效辐射的响应符合Michaelis-Menten反应曲线，模型在PAR<1800μmol•m-2s-1时模拟精度较高（P<0.01）。 在典型晴天条件下，5种红树植物的光合速率日变化都出现两个极大值（分别在11时和15时左右），中午前后光合速率较低，模型模拟光合速率日变化与实测数值日变化趋势一致。本模型能较好地模拟5种红树植物光合产量以及对环境因子的响应，模拟预测精度较高（P<0.01）。 以Ross和Nilson叶倾角分布模型为基础，分别建立了直接辐射和散射辐射在冠层内传输的子模型。冠层内的消光系数均有明显的日变化，且上午8时之前和下午16时之后随时间变化较大。在典型晴天条件下，单位土地面积日合成干物质总量（折合为CH2O）白骨壤为15.840g•m-2d-1，对于木榄、桐花树、秋茄、海漆其相应的值分别为 22.254 g•m-2d-1， 23.610 g•m-2d-1，24.525 g•m-2d-1和25.996 g•m-2d-1 。

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 .