Linking Changes in Plant Growth and Nutrient Stoichiometry With Nitrogen Enrichment in a Meadow Steppe

Abstract

Exogenous nitrogen (N) inputs can significantly influence the availability of N and other nutrients in terrestrial ecosystems. However, the connections between soil nutrient dynamics following N enrichment and plant nutrient uptake as well as plant growth responses within a community remain underexplored. Here, we examined the effects of N addition on the dynamics of several macro and micronutrients in soil and three dominant plants on a meadow steppe in China. The results showed that (a) the exchangeable Ca and Mg in the soil initially increased when the N addition rate was lower than 10 g N m⁻² yr⁻¹ and then decreased at higher N addition rates (10–50 g N m⁻² yr⁻¹), whereas the available P and extractable Fe, Mn, and Cu remained relatively stable at low N addition rates but increased at high N addition rates. (b) The response of plant nutrient concentrations and the stoichiometry of these nutrients to N addition was not only species-specific but also showed marked differences especially for those micronutrients. (c) Species with lower variation in nutrient concentrations, such as Leymus chinensis (Lc) and Thermopsis lanceolata (Tl), exhibited increased (for Lc) or stable (for Tl) biomass after N addition, whereas species such as Carex duriuscula, with greater nutrient variability, experienced reduced biomass. These findings suggest that soil acidification induced by exogenous N inputs alters soil nutrient availability and further results in imbalanced plant nutrient uptake and stoichiometries, which will affect the dynamics and structures of plant communities under global change scenarios.