The Photosynthetic Characteristics Of Precious Broad-Leaved Tree Species In South Subtropics And Their Relationship With Leaf Functional Traits

Guangxi is an important distribution area of precious tree species in south subtropics in China. The development of precious tree plantations has great significance of economy and ecology, especially the gradual replacement of the large area needle-leaved pure plantations of Pinns massoniana and Cunninghamia lanceolata. Photosynthesis is always the key and active field of academic research. The acquirement of photosynthetic characteristics of precious broad-leaved tree species has positive significance to develop and take advantages of the resource in south subtropics and guide the forestation of precious trees.In this study, light response curves and carbon dioxide response curves of 11 precious broad-leaved tree species are measured and fitted. The photosynthetic characteristics parameters were calculated and compared with each other. And correlation analysis was made combined with leaf functional traits. The main photosynthetic physiological characteristics of each species were preliminarily acquired. The main conclusions are as follows:1. The response curves were all well fitted. According to the fitted equations, the photosynthetic characteristics parameters can be calculated and compared. Net photosynthetic rate of the tree species in different levels of photosynthetic active radiation and carbon dioxide concentration can also be predicted based on the fitted equations.2. The photosynthetic characteristics parameters have obvious differences among the tree species. The maximum net photosynthetic rate of the tree species are between 6.999 μmol·m-2·s-1～18.194μmol ·m-2·s-1, the average value is 10.826 μmol·m-2·s-1. Tectona grandis L.f., Mytilaria laosensis and Castanopsis hystrix have relatively higher photosynthetic capacity, while Parashorea chinensis, Mesua ferrea and Paramichelia baillonii have lower photosynthetic capacity. Mesua ferrea, Tectona grandis L.f., Tsoongiodendron odorum and Dalbergia odorifera have relatively higher adaptability in high photosynthetic active radiation, while Manglietia glauce and Paramichelia baillonii have lower adaptability. Erythrophleum fordii, Castanopsis hystrix and Michelia hedyosperma have relatively higher utilization capacity in low photosynthetic active radiation, while Paramichelia baillonii, Parashorea chinensis, Tsoongiodendron odorum and Mytilaria laosensis have lower capacity.3. The correlations of characteristic parameters of light response curves:Initial quantum efficiency and light saturation point are highly significant positively correlation. Dark respiration rate is significantly positively correlated to initial quantum efficiency, light compensation point and light saturation point. The correlations of characteristic parameters of ambient carbon dioxide response curves:Light respiration rate is highly significantly positively correlated to initial carboxylation efficiency, and significantly positively correlated to maximum photosynthetic capacity. Initial carboxylation efficiency is highly significantly negatively correlated to ambient carbon dioxide compensation point, and significantly positively correlated to maximum photosynthetic capacity.4. The leaf functional traits of 11 precious tree species have significant differences in multiple levels. Among all the tree species: Highly significantly positive correlations are among the chlorophyll contents. Leaf potassium content and organic carbon content are significantly negative correlation. The SLA is significantly positively correlated to leaf nitrogen content, and significantly negatively correlated to N/P. The chlorophyll b content and leaf phosphorus content are significantly positive correlation. C/N and N/P are significantly negative correlation.5、No significant correlations are among the characteristic parameters of light response curves and the leaf functional traits. In characteristic parameters of ambient carbon dioxide response curves, the maximum photosynthetic capacity is significantly negatively correlated to C/N, and significantly positively correlated to N/P. The LDMC content and initial carboxylation efficiency are significantly negative correlation. The PNUE of the 11 precious tree species have significant differences. Manglietia glauce, Mytilaria laosensis, Castanopsis hystrix and Tectona grandis L.f. have relatively higher PNUE, while Paramichelia baillonii and Mesua ferrea have lower PNUE.