Extreme Warming Coordinately Shifts Root and Leaf Traits of Alpine Plants toward Conservatism

Climate change-induced shifts in plant functional traits can profoundly affect the stability of plant communities and ecosystem functions. However, the way in which leaf and root traits coordinate in response to climate extremes remains poorly understood. Here, we measured 16 leaf and root traits of 10 dominant plant species from a Tibetan alpine grassland to explore whether extreme warming leads to coupled/decoupled responses of root and leaf traits. We found that extreme warming increased the investment in defensive traits of plant leaves, but this came at the expense of plant growth. Specifically, warming increased the concentration of defensive compounds (tannin) in leaves by 44.4% but decreased leaf mass by 12.3%. More importantly, we found that the changes in leaf and root traits in response to extreme warming were coupled, resulting in both systems adopting more conservative strategies. For instance, extreme warming reduced leaf area and simultaneously increased root tissue density. Trait network analysis further supported this view, showing that extreme warming increased root edge density and decreased leaf modularity, indicating a more integrated network of leaf and root traits to enhance resource utilization efficiency. Our findings suggest that extreme warming may drive a coupled shift toward more conservative traits in both leaves and roots within alpine grasslands, with significant implications for predicting future ecosystem dynamics under escalating climate extremes.