| Ecological stoichiometry is the science of studing the balance of biological system energy and multiple chemical elements (usually C, N, P), which combined the principles of ecology and chemometrics. Ecological stoichiometry included the population, community and ecological system, and had become a new way to study global C cycle, soil nutrient analysis and plant nutrient use efficiency. We investigated the seasonal changes and ecological stoichiometry of soil and foliar C, N, P concentration and C:N, C:P, N:P ratios of subtropical evergreen broad-leaved forest in Shitai, Anhui Province. The results showed as folows.(1) Foliar C, N, P concentrations and thheir stoichiometric characteristics of the different kinds of plants. Foliar C concentrations were ranged from 400.08 to 519.36 mg/g, N from 5.15 to 15.39 mg/g and P from 0.30 to 0.97 mg/g for 28 major species. The mass ratio of C:N, C:P and N:P was 29.99-92.25,467.01-1443.81 and 10.01-29.29, respectively. There was a strong correlation between N and P, as well as C: N and C:P. The change of N:P ratio is mainly determined by the P concentration. Due to the limitation of P, their C:P ratios were higher. In other words, for the limitation elements, plant will have a higher use-efficiency. This also reflects the adaptation strategy of plants to environment.(2) Stoichiometric characteristics of different types of plants. The foliar C concentration of trees and shrubs were significantly higher than that of herb and liana. It means that the tree and shrub species had higher C reserve capacity. As for the relationships among C, N, P concentrations in the different types of plants, the foliar C: N ratios ranked as:shrubs (59.68)> trees (51.56)> herbs (44.50). The C:N ratios were significant different between shrub and herb species. The foliar C:P ratios ranked as shrubs (1043.4)> herbs (818.78)> trees (808.35). The C:P ratios were significantly higher in shrubs than in trees and herbs. These results indicate that species of evergreen broad-leaved forest in Shitai had higher use-efficiency of N and P. The N use-efficiency of shrubs was higher than other types of plants.(3) Seasonal dynamics of foliar stoichiometry characteristics. The foliar C concentrations of three dominant tree species showed a slight decrease in spring and summer and an increase in autumn and winter. The N concentrations were relatively high, while the P is relatively low. With comparison of C:N and C:P ratios, we found that N, P use efficiencies were the highest for Castanopsis eyrei, followed by Symplocos stellaris and lowest for Dendropanax dentiger. The annual trends of foliar N, P concentrations and C:N, C:P and N:P ratios were not clear for the three dominant species. The N concentration was significantly and positively correlated to P concentration. The annual trends of C:N and C:P ratios were opposite to those of N and P. The N:P ratio and P concentration showed the similar patterns. The results indicated that foliar N, P concentrations played a predominant role in determining C:N and C:P ratios and N:P ratio was controlled by P concentration. The variation coefficient of these parameters ranked as P>C:P>N:P>N>C:N>C. Factorial analysis of variation for these parameters showed that foliar C, P, C:N, C:P and N:P ratios were mainly determined by plant species, fowolled by months, and their interaction was lowest.(4) Relationship between soil and plant C, N, P ecological stoichiometry. Foliar N concentration of Dendropanax dentiger was positively correlated with soil total N concentration, which confirmed there is a close relationship between soil and plant nutrients. There was no significant correlation in Castanopsis eyrei and Symplocos stellaris. As to P concentration, there were not significant relationships between soil and three dominant species. Those relationships indicated that the uptake of N and P is a relatively active process, and different species had the different strategy for nutrient absorption. |
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