Linkages of plant and soil C:N:P stoichiometry and their relationships to forest growth in subtropical plantations

Ecological stoichiometry plays important roles in ecosystem dynamics and functioning, but relationships between above- and belowground stoichiometry and stoichiometric effects on the growth of different plant functional groups in forests remain poorly understood. In an age sequence of 2-, 4- and 6-year-old Eucalyptus plantations in subtropical China, we examined C, N and P concentrations and their ratios in the soil and leaves. Each plantation was divided into overstory and understory plant functional groups. The relationships between stoichiometric characteristics and forest growth were analyzed. Soil C and P decreased in the Eucalyptus age sequence, which led to changes in soil stoichiometric characteristics. Leaf C:P and N:P ratios were higher for Eucalyptus trees than for understory plants because of the low P concentrations in Eucalyptus leaves. Soil and plant N:P ratios were strongly related. Understory biomass was positively related to N:P ratios, while overstory growth was negatively related to N:P ratios. Our results suggest that nutrient concentrations in soil and plants are tightly linked in Eucalyptus plantations and that P limitation increases with stand age. Stoichiometric characteristics appear to mediate forest properties and functions under nutrient limitation in subtropical regions.