Abstract: [Objective] In this study, quantitative characteristics of leaf photosynthetic pigments indexes of plant species in Karst rocky mountains in Guilin were analyzed to dig up the main shade tolerance indicators by using multivariate statistical method. Furthermore, the different plant species were classified based on the degree of shade tolerance to investigate the physiological characteristics of photosynthetic pigments by which the different plant species adapt their sites in the Karst rocky mountains. Thus, the study would provide a corresponding theoretical basis in restoring the degraded Karst rocky mountain habitat. [Method] A total of 50 common plant species growing in Karst rocky mountain of Guilin were selected to measure the leaf photosynthetic pigment indicators, including chlorophyll a (Chl a), chlorophyll b (Chl b), Carotenoid (Car), Chl (a+b) contents and Chl a/b. One-way ANOVA and post hoc Duncan test were used to test the significance of difference in each photosynthetic pigment indicator among the 50 plant species. Pearson correlation analysis was used to test the correlation between one photosynthetic pigment indicator and another. Principal component analysis (PCA) was used to find the main variables among the photosynthetic pigment indicators. The optimal partition of ordered sample method was used to divide the degree of shade tolerance among the 50 plant species based on the PCA ordination of shade tolerance. [Result] The average values of Chl a, Chl b, Car, Chl (a+b) and Chl a/b of the 50 plant species were 2.89 mg·dm^-2,1.19 mg·dm^-2,0.59 mg·dm^-2,4.07 mg·dm^-2, and 2.47, respectively. There were significant differences in all the 5 photosynthetic pigment indicators among the 50 plant species. There were significantly positive correlations among Chl a, Chl b, Car and Chl (a+b), and a negative correlation between Chl a/b and Chl b, and no significant correlation between Chl a/b and Chl a. The main differences of photosynthetic pigment indicators among the 50 plant species were the Chl (a+b) and chl a/b. The 50 plant species were divided into 3 types: type I with strong shade tolerance, type II with the characteristics combining shade plant and heliophyte, and type III with the characteristic of heliophyte or mesophyte. [Conclusion] The shade tolerance of the 50 plant species, which was decided based on the leaf chlorophyll content and Chl a/b ratio, was overall in accordance with their performance in the field, and the leaf chlorophyll contents and Chl a/b ratio were the important indicators which can reflect the shading resistance of plant. These research results would provide a reference on species selection in carrying out vegetation restoration and reconstruction in this area.

Key words: photosynthetic pigments, shade tolerance, principal component analysis, optimal partition of ordered sample method, Karst rocky mountain of Guilin