Temperatures in Florida are expected to increase ~5°C by 2100. North Florida will shift from a temperate/subtropical climate to a tropical climate within 30 years which could alter the forest composition and productivity. We conducted a field experiment using warming chambers to determine how warming impacts the physiological performance of four species in North Florida: Serenoa repens (saw palmetto), Andropogon glomeratus (bushy bluestem), Pinus palustris (longleaf pine), and Quercus laevis (turkey oak). Over one year we measured rates of leaf net photosynthesis (A) and stomatal conductance to water vapor (gs) on seedlings of each species under ambient and warmed treatments. We hypothesized climate warming effects on leaf physiology would vary among species and with changes in soil moisture. We predicted species with tropical distributions and adaptations to high temperatures (palmetto and C4 grass) would increase photosynthesis with warming compared to species with temperate distributions (oak and pine), and across species, reductions in soil moisture would diminish the positive effects of warming on photosynthesis. We found photosynthesis increased with warming in S. repens and A. glomeratus, did not change with warming in Q. laevis, and decreased with warming in P. palustris. Photosynthetic responses to warming did not vary with soil moisture in both S. repens and A. glomeratus. However, warming reduced photosynthesis in Q. laevis and P. palustris when soil moisture was low. These results suggest climate warming might benefit grasses and palmetto at the expense of native tree species, foreshadowing a shift in forest structure, composition, and productivity
