Comparative on plant stoichiometry response to agricultural non-point source pollution in different types of ecological ditches.

Long-term agricultural development has led to agricultural non-point source (NPS) pollution. Ecological ditches (eco-ditch), as specific wetland systems, can be used to manage agricultural NPS water and achieve both ecological and environmental benefits. In order to understand which type of eco-ditch systems (Es, soil eco-ditch; Ec, concrete eco-ditch; Eh, concrete eco-ditch with holes on double-sided wall) is more suitable for plant nutrient balance meanwhile reducing NPS water (total nitrogen [TN], about 10 mg/L; total phosphorus [TP], about 1 mg/L), it is essential to evaluate the plant (Vallisneria natans) stoichiometry response to water in different types of eco-ditches under static experiment. The results indicated that there were no significant differences in TP removal efficiency among three eco-ditches, yet Eh systems had the best TN removal efficiency during the earlier experimental time. Addition of agricultural NPS water had varying effects on plants living in different types of eco-ditch systems. Plant organ stoichiometry of V. natans varied in relation to eco-ditch types. Plant stoichiometry (C:N, C:P, and N:P) of V. natans in Eh systems could maintain the homeostasis of nutrients and was not greatly affected by external changing environment. V. natans in Es systems can more easily modify the nutrient contents of organs with regard to nutrient availability in the environment. Our findings provide useful plant stoichiometry information for ecologists studying other specific ecosystems.