Biochar’s influence on plant competition differs under present and future climate conditions

The rise in atmospheric carbon dioxide (CO 2 ) concentrations from human activity is projected to lead to a 2–4°C increase globally by the end of the 21st century. This increase has far-reaching consequences for plant community structure and soil carbon storage. This has led to a focus on long-term carbon storage in soils through nature-based solutions and management strategies such as biochar additions to soil. Biochar additions to soil can impact both soil carbon stocks and plant community structure. However, it remains unclear whether biochar impacts on plant communities will remain consistent under future, warmer climates. To examine the impact of biochar and elevated temperature on the performance of competing grassland species, we grew individuals of two perennial grass species together and in monoculture, in the presence and absence of biochar and soil warming, in a fully factorial design. We found that under elevated temperatures 1) interspecific competitive ability of both species was significantly reduced in the absence of biochar and 2) the addition of biochar mitigated the effect of warming and restored the competitive ability of each species. Our results suggest that the addition of biochar may increase the persistence of certain species under future climatic scenarios, where it may have been eliminated by interspecific competition under warmer temperatures without biochar. It also suggests that, under future climatic scenarios, biochar additions may directly influence soil carbon storage and indirectly by altering plant community structure, making biochar a more effective approach to climate change mitigation. • Experimental warming reduced grassland species competitive ability without biochar. • Biochar restored the competitive ability of each species under warming. • Biochar effect on competitive interactions may depend on climatic conditions. • Biochar may allow for species persistence under future climatic scenarios.