Seasonal Dynamics of Photosynthetic Physiology and Soil Environment of Typical Wetland Plants in the Minjiang Estuary

To explore the relationship between photosynthesis of vegetation in the Minjiang River Estuary and soil moisture content and pH,plots of Kandelia obovata Sheue,Phragmites australis and Cyperus malaccensis were set up in the Minjiang River Estuary Wetland. The net photosynthetic rate (P_n),transpiration rate (T_r), intercellular CO₂ concentration (C_i) and stomatal conductance (G_s) of the three plants were measured in spring,summer,autumn and winter,as well as the soil moisture content and pH at 0—80 cm depth. The results showed that the P_n,T_r and G_s of Kandelia obovata Sheue reached the highest in summer,and C_i was the highest in winter;the P_n and G_s of Phragmites australis were the highest in summer,and T_r and C_i were the highest in spring;the P_n and T_r of Cyperus malaccensis were the highest in spring,G_s was the highest in summer,and C_i was the highest in winter. The soil moisture content generally increased with the increase of soil depth. The soil pH values of the wetland vegetation were weakly acidic. Correlation analysis showed that P_n was significantly correlated with pH of the 0—20 cm soil layer,and T_r was significantly correlated with the pH of each soil layer. In conclusion,the photosynthetic physiological characteristics of different wetland vegetation show obvious seasonal differences and are closely related to soil moisture content and pH value. Among them,the transpiration rate is particularly sensitive to the changes in soil pH at each soil layer,and the two show a significant correlation.