Compensatory responses of leaf physiology reduce effects of spring frost defoliation on temperate forest tree carbon uptake

Spring frosts can defoliate trees, reduce canopy carbon assimilation, and alter interspecific competition dynamics. These events may become more common with climate change, but our understanding of the associated ecological impacts is limited by stochastic nature their occurrences. In 2020, a late spring frost defoliated oak ( Quercus spp.), not co-occurring maples Acer spp.) across temperate broadleaf forests Hudson Highlands in southern New York State, U.S.A. Defoliation impacted 60% this region’s delayed full leaf expansion oaks ∼17 days. We used event as an opportunity to advance how leaf-level physiology, radial growth, dynamics mature trees respond frost-induced defoliation. quantified photosynthetic capacity, stomatal conductance, water-use efficiency (WUE), well basal area increment red Q. rubra ) non-defoliated maple A. rubrum 2020 (“defoliation year”) 2021 (“reference year”). Oak defoliation provided competitive edge terms capacity early growing season. However, second cohort leaves that developed following had capacities were 3–4 times higher than half season, likely facilitated rates conductance. The season mean for year significantly maples. Red tended be during both reference years. For species was year, reasons remain unclear. Taken together, these findings demonstrate temporal patterns photosynthesis are altered events, enhanced negative effects mitigate advantages conferred undefoliated tree species. suggest species’ ability compensate essential accurately predict extreme on ecosystem processes.