The Effects Of Simulated Acid Rain On Photosynthetic Eco-physiology Of Four Common Broad-leaved And Conifers Seedlings In Zhejiang

As the human activity increases, the acid rain in Zhejiang Province became rather serious in recent years: the pH value of rain declined, the frequency of acid rain increased, and the acid rain area increased.The serious acid rain must have a certain impact on the forest ecosystem in Zhejiang Province. The serious acid rain in Zhejiang Province may bring some significant impact on its forest ecosystem. The acid rain could affect the physiological structure species, the interaction between species, and even change the genetic characteristic of species, thereby change the species composition, biological structures and function of the whole forest system. In the way, we chose the seedlings of four typical subtropical species: Quercus glauca, Cyclobalanopsis myrsinaefolia, Pinus massoniana, Cunninghamia lanceolata, measured their seasonal variations and annual variation of photosynthesis, the seasonal variations of chlorophyll fluorescence, chlorophyll content, height and diameter, which was under the different intensity of the acid rain. Try to analyze the effects of acid rain on photosynthesis of four seedlings. We offer some methods for selecting acid-resistant species. The experiment set three acid rain treatments: pH2.5, pH4.0, pH5.6(CK). The results show that:1) Through the photosynthesis of four plant seedlings at different seasons, we found that: Acid rain has a dramatic effect on the photosynthesis seasonal changes of Quercus glauca, Cyclobalanopsis myrsinaefolia, Pinus massoniana, Particularly Cyclobalanopsis myrsinaefolia under the pH2.5 treatment have an obvious inhibiting effect. The parameters Pnmax,LCP,LSP indicates the photosynthetic have a stress trend of Cyclobalanopsis myrsinaefolia under the pH2.5 treatment; Pinus massoniana under pH4.0 treatment in summer and pH2.5 treatment in Autumn,Cunninghamia lanceolata under pH2.5 treatment in summer and pH2.5 treatment in Autumn have a effect of promotion. Quercus glauca under pH4.0 treatment have an effect of promotion in autumn. In the mode of dark respiration rate, especially in summer under pH2.5 treatments the dark respiration rate of Quercus glauca and Cyclobalanopsis myrsinaefolia reduced, the dark respiration rate of Pinus massoniana under pH4.0 treatments and Cunninghamia lanceolata under pH2.5 treatments increased. Analyzing the gas exchange parameters, we found that the stomatal conductance, the stomatal CO₂ concentration and transpiration rate of the four plant seedlings under different acid rain treatment have the same order as the net photosynthetic rate. Pinus massoniana, Cunninghamia lanceolata in autumn have a higher water use efficiency, while Quercus glauca have a lower water use efficiecncy.2) Analyzing the diurnal net photosynthetic curve, we found that:The diurnal net photosynthetic curves of four plant seedlings have the same tendency as their net photosynthetic curve. Analyzing the relationship between the Diurnal net photosynthetic rate and the net G_s, C_i, T_r, Wue and light intensity, we conclude that the net photosynthetic curve and the net G_s have a high correlation.3) From the data of Chlorophyll Fluorescence, Chlorophyll content, height and diameter, we found acid rain have the biggest effects on Chlorophyll Fluorescence of Quercus glauca. The maximal photochemical efficiency of PSâ…¡and the potential activity of PSâ…¡of Quercus glauca were significantly higher. F_v/F_o, F_v/F_m of Cunninghamia lanceolata under pH 2.5 and pH 4.0 treatments were significantly higher. The F_v/F_o, F_v/F_m of Cyclobalanopsis myrsinaefolia and Pinus massoniana has a little change. The result of Chlorophyll content show that the pH2.5 and pH4.0 improve the Chlorophyll content of Quercus glauca in summer and autumn, the pH2.5 treatment improve the Chlorophyll content of Cyclobalanopsis myrsinaefolia. The pH2.5 and pH4.0 treatments decrease the Chlorophyll content of Pinus massoniana in autumn. The pH2.5 and pH4.0 treatment improve the Chlorophyll content of Cunninghamia lanceolata. The whole biomass data in 2009 shows that, the acid rain has a biggest effect on the height of Pinus massoniana. The height under the pH2.5 and pH4.0 treatment is higher than CK. The diameters of four plant seedlings have no dramatic change under each treatment. The Chlorophyll Fluorescence and Chlorophyll content have no significant correlation.4)The data of two years photosynthetic shows that, the reaction of Quercus glauca reacted to the acid rain of pH4.0 is promotive in 2007, while no significant difference in 2009. Cyclobalanopsis myrsinaefolia reacted to the acid rain no significant difference in2007, while of pH2.5 is inhibition. Pinus massoniana reacted to the acid rain no significant difference in 2007, while of pH4.0 is promotion in 2009. Cunninghamia lanceolata reacted to the acid rain no significant difference in 2007, while of pH2.5 is promotion in 2009.Through three years acid rain treatment, the photosynthetic of Pinus massoniana and Cunninghamia lanceolata have a promotion under pH2.5, Quercus glauca and Cyclobalanopsis myrsinaefolia have an inhibition under acid rain.