Inter- and intra-specific phenotypic variation of ecological stoichiometric traits in a mixed-oak secondary forest in China

Abstract

Ecological stoichiometry provides a framework for the balance and flow of elements between organisms and ecosystems. Elemental phenotypes have an important influence on the environmental adaptation and ecological evolution of plants. There have been few reports on inter- and intra-specific phenotypic variations of ecological stoichiometric traits for congeneric species in a mixed forest although such variations are well- documented at the species level at global, regional and local scales. In this study, total carbon (TC), nitrogen (TN), phosphorus (TP) and potassium (TK) were measured in leaves and the elemental phenotypes were statistically analyzed in four species of oaks—Quercus fabri, Q. serrata var. glandulifera, Q. acutissima and Q. variabilis—in a mixed-oak secondary forest in Yushan, Jiangsu, China. The average element concentrations in the four oak species were not relatively higher than previously reported for oaks from world and Chinese flora. Ecological stoichiometry traits were correlated with tree height and diameter at breast height, indicating that phosphorous and potassium were positively correlated with tree size, while carbon was negatively correlated, especially the relationship between oak growth and total carbon or total phosphorus was obvious, and the study concluded that this was because plant growth depended on phosphorus storage and had opposite effects on leaf carbon accumulation. Based on tree plasticity index and the coefficient of variation, there was medium variation in element concentrations. The plasticity index of total carbon levels was the lowest, and that of potassium the highest. Principal component analysis and cluster analysis showed that the intra-specific variation among the four oak species was higher than inter-specific variation. From the perspective of nutrient supply and ecological adaptation, this study creates a foundation for the management of secondary oak forest stands.