Sugar maple (Acer saccharum) is one of the dominant tree species in North America and is of both great ecological and economic importance. Countless studies have evaluated sugar maple’s biology and ecology, but recent studies suggest that in light of anthropogenic climate change it may not be well adapted to persisting over much of its current range. In this study, employing both common garden and reciprocal planting methods, we consider geographic variation in sugar maple’s photosynthetic properties for seedlings derived from a southern, central, and northern population.   

Results/Conclusions

Seeds collected in Tennessee, Illinois, and northern Michigan were grown under common laboratory conditions and in two experimental plots in Illinois and Michigan. For all seedlings growing under these varied conditions we measured leaf photosynthesis with an open gas exchange infrared gas analyzer. Measurements included dark respiration, compensation point, maximum photosynthesis (Amax), quantum use efficiency, light saturation point, and water use efficiency (WUE). In the Michigan field site, seedlings derived from Michigan seeds had significantly higher carbon gain than those from Tennessee or Illinois. At the Illinois field site, seedlings from Tennessee had significantly greater carbon gain and light saturation points than seedlings derived from Illinois or Michigan seeds. Under controlled laboratory conditions, Tennessee seedlings had significantly greater maximum photosynthesis rates and light saturation points than Illinois or Michigan seedlings.  There was no geographic variation in WUE for seedlings growing in Michigan, but the Tennessee and Michigan seedlings had greater WUE at the Illinois field site than did Illinois seedlings. In the laboratory, Tennessee seedlings had significantly lower WUE than the two other seed sources.