Synergistic interactions between zinc and nitrogen addition in promoting plant Zn uptake as counteracted by mowing management in a meadow grassland.

Purpose: In nitrogen (N)-fertilized grasslands, mowing removes large quantity of nutrients from ecosystems due to plant biomass removal at higher levels. This study tested the hypothesis that if mowing could counteract the synergistic interactions of exogenous zinc (Zn) and N supply on plant Zn uptake. Methods: Our hypothesis was tested with three dominant species (Leymus chinensis, Carex duriuscula, and Stipa baicalensis) in a field experiment exposed to Zn addition, N addition and mowing treatments. A pot experiment using a low-Zn soil was further conducted to explore mechanisms of N-driven changes in plant-soil Zn dynamics. Results: Zinc addition increased soil available Zn across all treatments. However, effects of Zn addition on plant Zn uptake were treatment- and species-specific given by higher Zn contents in L. chinensis under N addition, in C. duriuscula under mowing, and in S. baicalensis under mowing and N addition. Nitrogen addition synergistically interacted with Zn addition to increase Zn uptake of L. chinensis. Meanwhile, N addition reduced Zn uptake of C. duriuscula without Zn addition, mainly due to plant biomass suppression in the presence of more dominant L. chinensis. Mowing counteracted the synergistic effect of combined N and Zn addition on Zn content of L. chinensis through biomass removal and lowering soil moisture. Conclusion: Our results indicated that plant Zn uptake was mainly driven by soil Zn availability and species-specific responses of biomass to N addition and mowing. Moreover, counteractive mowing effect on the synergisms between Zn and N addition might necessitate grassland Zn fertilization. [ABSTRACT FROM AUTHOR]