Contrasting Responses of Four Steppe Grasses to Warming and Precipitation Variability

Climate change, characterized by warming and precipitation variability, restricted the growth of plants in arid and semi-arid areas, and various functional traits are impacted differently. Comparing responses of functional traits to warming and precipitation variability and determining drought threshold of dominate steppe grasses from Inner Mongolia can enable the identification and monitoring of water stress effects. Simulation experiments were performed under ambient temperature and warming (+1.5°C and +2.0°C) with different precipitation treatments (-30%, -15%, ambient, +15%, and +30%), using four Stipa species (S. baicalensis, S. bungeana, S. grandis, and S. breviflora) from Inner Mongolia steppe. We found that the functional traits of the four species differed in their responses to precipitation, but they shared common sensitive traits (root/shoot ratio, R/S and specific leaf area, SLA) under ambient temperature condition. Warming increased the response of the four grasses to changing precipitation, and these differences in functional traits resulted in changes to their total biomass, with leaf area, SLA and R/S making the largest contributions. Drought thresholds of the four grasses were identified, and warming led to their higher optimum precipitation requirements. The four steppe grasses were able to adapt better to mild drought (summer precipitation decreased by 12%-28%) when warming 1.5°C rather than 2.0°C. These results indicated that if the Paris Agreement to limit global warming to 1.5°C will be accomplished, this will increase the probability for sustained viability of the Stipa steppes in the next 50-100 years.