Abstract: Gleditsia sinensis is one of the top ten recommended tree species for ecological restoration in the Yellow River Basin. Clarifying the ecological stoichiometry characteristics of G. sinensis community is helpful to the scientific configuration and optimization of plant communities and the effective construction of green ecological barrier along the Yellow River desertification region. By using the method of substitution of space for time, different diameter at breast height (DBH) classes of G. sinensis (large, medium, and small trees) were analyzed and sampled by trunk analysis. LSD-mean multiple comparison method was used to quantify the differences in biomass, total carbon content (TC), total nitrogen content (TN), carbon-to-nitrogen ratio (C/N) and carbon density (CD) in organs of G. sinensis among different DBH classes. The results showed that there were significant differences in the ecological stoichiometric characteristics in organs among different DBH classes (P<0.05). There were significant differences in stem biomass, TN and C/N of branch between large and small trees. The TC of branch and TN of leaf for different DBH classes exhibited a sizedependent relationship. The TC and TN in leaves of different DBH classes were higher, and the C/N showed an increasing trend. In addition, there was a significant positive correlation between the proportions of the biomass of each organ of trees across different DBH classes and the proportions of CD, as well as the proportions of TC and TN. These results are of great significance for plant arrangement model and regional ecological restoration of the fragile ecosystems in the Yellow River desertification region.

Key words: Yellow River Basin, Gleditsia sinensis, diameter class, carbon and nitrogen, ecological stoichiometry