Carbon, Nitrogen And Phosphorus Stoichiometry Of Wetland Plants In The Poyang Lake

Ecological stoichiometry of carbon, nitrogen and phosphorus reflects balance and coupling between the elements. It affects series of physiological and ecological processes, such as plants growth, nutrient cycling, food and nutrition relations, species composition and diversity. Moreover, ecological stoichiometry provides a new method for exploring the unified theory from the individual to ecosystem level, which received extensive attentions of researchers. Currently, the regional C:N:P stoichiometry pattern and its driving factors are important fields of ecological stoichiometry researches, which results not only help to reveal the convergence and differentiation between species stoichiometry, but also play important role in understanding and predicting responses of ecosystem structure and function to global change.Poyang Lake is the largest freshwater lake in China. It developed emergent, hygrophyte, floating and submerged plant communities along the water level gradient. The communities are usually dominated by one or two species, with relative simple structures. In the study, we measured carbon, nitrogen and phosphorus concentrations of different plant organs(leaf, stem and root) and top soils during the non-flooded season in typical Poyang Lake wetlands. Subsequently, we analysed carbon, nitrogen and phosphorus stoichiometry in various plant organs. The objectives of this study were(1) to clarify the spatial pattern of nutients stoichiometry in Poyang Lake wetlands, and(2) to discuss the stoichiometric relations among the plants organs. The main results are as follows:(1) Averagely, carbon, nitrogen and phosphorus concentrations ragned from 218.65 to 464.46 mg·g-1, 5.02 to 46.97 mg·g-1 and 0.48 to 4.15 mg·g-1, respectively. The C:N, C:P and N:P ratios varied from 6.88 to 86.66, 86.78 to 846.64 and 3.52 to 34.82, respectively. The nitrogen concentrations in plant organs were significantly correlated with phosphorus concentrations.(2) The emergent plants significantly differed in carbon, nitrogen and phosphorus concentrations and their stoichiometry for various organs. The carbon, nitrogen and phosphorus concentrations were in the order of leaf>stem>root. Correlation of elements stoichiometry was not significant.(3) The carbon, nitrogen and phosphorus concentrations of hygrophyte were in the order on leaf>stem>root. Correlations between leaf, stem and root carbon concentrations, as well as leaf and stem nitrogen concentrations, were significant. The correlations of phosphorus concentrations among leaf, stem and root were not significant.(4) The carbon, nitrogen and phosphorus concentrations of floating plants were in the order of leaf>stem>root. Except the nitrogen and phosphorus concentrations of root, the correlations among other floating plants elements were not significant.(5) The carbon and nitrogen concentrations in submerged plants are in the order of leaf>stem>root, but stem>leaf>root for phosphorus concentrations.(6) The correlations of nitrogen concentrations among leaf, stem and root were significant. The correlation of phosphorus concentrations between leaf and stem was significant, but not significant for leaf and root.(7) The elemental concentrations varied significantly with plant species and among leaves, litters, and top soils. Leaves had significantly higher levels of carbon, nitrogen, and phosphorus concentrations than litters and soil. Soil C:N, C:P, and N:P stoichiometry was closer to that of litters, rather than plant leaves. Changes in the C:N ratio of litters could explain 35% of soil C:N ratio variability, whereas 18% of soil N:P ratio variability could be explained by litter N:P.