Future climate alleviates stress impact on grassland productivity through altered antioxidant capacity

- We examined stress responses of grassland communities in current and future climate.
- Stress-induced biomass reduction was smaller in future than in current climate.
- Future climate induced changes in sugar metabolism.
- Future climate increased the levels of total antioxidant capacity and polyphenols.

Predicting future ecosystem functioning requires a mechanistic understanding of how plants cope with different stressors under future climate conditions with elevated CO2 concentrations and warmer temperatures. Nonetheless, studies of stress responses under combined elevated CO2 and warming remain scarce.We assembled grassland communities in sunlit, climate-controlled greenhouses and subjected these to three stressors (drought, zinc toxicity, nitrogen limitation) and their combinations. Half of the communities were exposed to ambient climate conditions (current climate) and the other half were continuously kept at 3 °C above ambient temperatures and at 620 ppm CO2 (future climate).Across all stressors and their combinations, future climate-grown plants coped better with stress, i.e. above-ground biomass production was reduced less in future than in current climate. Among several tested potential biochemical and ecophysiological stress-relief mechanisms, we found three mutually non-exclusive mechanisms underpinning an improved stress protection under future climate conditions: (i) altered sugar metabolism; (ii) up-regulated levels of total antioxidant capacity and polyphenols; and (iii) more efficient use of ascorbate and glutathione as antioxidants.