Interannual variations in the responses of plant functional traits to mowing and nitrogen addition in an Inner Mongolian typical steppe

Functional traits can regulate how plants respond to changes in the ambient environment; however, they can also be influenced by changes in the environment, resulting in variations among ecosystems and years. Based on a 4-year manipulative mowing and nitrogen addition experiment on a typical Inner Mongolian grassland, we analyzed and explored plant functional trait responses to mowing and nitrogen addition and analyzed the strengths and effect of both sampling years and treatments on these plant functional traits. This study focused on 10 plant functional traits, including plant height, leaf area, leaf carbon and nitrogen content, of three dominant species: i.e. Leymus chinensis, Stipa krylovii, and Cleistogenes squarrosa. The results indicate that mowing significantly reduced the height of the three species. Nitrogen addition alone, and in combination with mowing, increased the leaf nitrogen content in the dominant species. This led to a decreased leaf carbon-to-nitrogen ratio, but had almost no impact on the plasticity of the plant functional traits. Potentially because of the cross-year variation in precipitation, sampling years led to pronounced interannual variability in both plant functional traits and their responses to treatments. These results imply that accurately predicting the responses of plant functional traits may become increasingly challenging with increased interannual fluctuations in precipitation while considering the context of land-use practices could enhance accuracy.