Investigating possible effects of climate change on tree recruitment: Responses of abundant species to water stress in Gorongosa National Park

• Climate change is predicted to bring more droughts to southern Africa, and the ability of seedlings to tolerate drought will affect future patterns of recruitment
• Combretum adenogonium, Vachellia xanthophloea, and Faidherbia albida are abundant tree species found across a moisture gradient
• A greenhouse study showed water stress had less of an effect on C. adenogonium than the two more mesic species
• V. xanthophloea responded to water stress increasing its root:shoot ratio
• F. albida biomass decreased above- and belowground, but population level differences indicate individuals from drier areas invest more in roots undermoderate water stress

Climate change is predicted to manifest in more extreme droughts in large parts of Africa. Investigating how species' distributions may change in response to drought is therefore necessary for understanding ecosystem functioning, and it will also help inform land managers regarding changes in resource availability. This work can be approached at the species and population levels with greenhouse studies that demonstrate changes in plant growth and allocation patterns in response to water stress. The present study contributes to this research need by investigating the effects of water stress on seedlings of three abundant tree species at Gorongosa National Park (GNP). GNP is the site of intense conservation efforts and is predicted to suffer from increased drought in the near future. Combretum adenogonium, Vachellia xanthophloea, and Faidherbia albida are abundant trees in the park and are found across a moisture gradient. A water stress treatment showed that seedlings of C. adenogonium may be least affected by future drought, and V. xanthophloea may be able to adapt to drought by maintaining root biomass even as aboveground growth decreases. F. albida is found in the wettest areas of the park where trees grow, and population level differences show individuals from a drier region invest more in roots under moderate water stress. Together, these data suggest that these three species may continue to establish under drought conditions, but if water stress is prolonged, the ranges of V. xanthophloea and F. albida may contract.