Sprouts of shoot-clipped oak (Quercus alba and Q. robur) germinants show morphological and photosynthetic acclimation to contrasting light environments

Sprouting by woody plants can increase species resilience to disturbance and foster regeneration during periods with little recruitment from seed. Though sprouting often plays a critical role in oak forest regeneration, there is little information available on sprouting capacity and sprout physiology at the seedling stage, particularly for new germinants. This study compared sprouting capacity and sprout photosynthesis of shoot-clipped germinants of two temperate oaks established in contrasting light environments. We studied the North AmericanQuercus albaand the EuropeanQ. robur, both are in the sectionQuercusand appear to share similar biological and ecological requirements. Sprouting capacity for both species was enhanced under high light availability (29% more sprouts per plant), a response not previously noted for oak germinants. Seedling sprouts acclimated to high light with a 34% decrease in leaf area ratio, a 56% increase in leaf mass per area, and a 49% increase in the light-saturated maximum photosynthetic rate. Though both species appeared similarly adapted to shoot loss, a greater sprouting capacity (29% more sprouts per plant) and plant-level net photosynthesis (73% higher) was observed forQ. robur, regardless of light environment. As naturally regenerated oak seedlings in forest understories often experience disturbance or stress resulting in shoot loss or die-back, our results highlight the importance of the light environment during early plant development. Our comparison of temperate oaks from different continents should facilitate exchange of successful stand regeneration practices within the range of temperate oak forests.