Ecosystem stability is determined by plant defence functional traits and population stability under mowing in a semi-arid temperate steppe

1. As a common grassland management practice in many high-latitude regions worldwide, mowing has great impacts on grassland functioning and stability. Species richness, species asynchrony and species stability have been suggested as central in responses to environmental change. Mowing can evoke plant defence system due to physical damages to plants. However, no studies have comprehensively evaluated the role of plant defence functional traits, species richness, species asynchrony and stability in ecosystem functioning under mowing regimes across timescales.2. In this study, we set up short-term (4 years) and long-term (16 years) mowing experiments with three stubble heights (control, 10 cm, 2 cm) in a temperate steppe of Inner Mongolia. We investigated the effects of mowing-induced changes in distribution metrics associated with plant defence traits, that is mean, variance, skewness and kurtosis of trait distribution, on ecosystem stability of grassland communities using structural equation modelling.3. We found that grassland ecosystem stability was enhanced by increasing mowing duration and decreasing stubble height. Mowing-induced increase in abundance and diversity of plant defence traits contributed to greater ecosystem stability by enhancing species asynchrony and population stability. Moreover, we found that mowing enhanced the abundance and diversity of plant defence traits of dominant species and contributed to population stability and species asynchrony, thus enhancing temporal stability of grassland ecosystems.4. These results demonstrate the important roles of plant defence traits in maintaining stability of grasslands under mowing, and highlight that, in addition to species richness, asynchrony and population stability, plant functional defence trait acts in stabilizing ecosystem functions under human-induced environmental changes.