Skip to main content
Dryad

Photosynthetic induction and sunfleck responses of three shade-tolerant temperate saplings

Schedlbauer, Jessica1; Paynter, Sarah1

Published Mar 06, 2025 on Dryad. https://doi.org/10.5061/dryad.bzkh189kb

Data files

Mar 06, 2025 version files 3.32 MB

Click names to download individual files

Abstract

Novel understory tree species composition has arisen throughout forests of the eastern U.S. as various, often human-caused, pressures have led to regeneration mismatch between trees in the forest canopy and understory.  Physiological attributes supporting the relative success of these novel understory tree communities are poorly characterized.  We sought to examine photosynthetic induction and sunfleck responses in three shade-tolerant understory tree species now common in the U.S.’s Mid-Atlantic region.  Focal species included the non-native Acer platanoides, as well as the natives Acer rubrum and Fagus grandifolia.  Three experiments were performed on three individuals of each species at three independent study sites in the broadleaf forests of southeastern Pennsylvania, USA.  The experiments were: (1) a photosynthetic induction experiment where uninduced leaves were first exposed to low light, followed by saturating light and measured until photosynthesis and stomatal conductance stabilized, (2) 30 second sunfleck experiments in which uninduced leaves were exposed to low light followed by a series of five 30 second saturating sunflecks, with two minutes of low light provided between each sunfleck, (3) 60 second sunfleck experiments in which uninduced leaves were exposed to low light followed by a series of five 60 second saturating sunflecks, with two minutes of low light provided between each sunfleck.  Findings show fairly similar and rapid photosynthetic induction responses among species, consistent with expectations for shade-tolerant tree species.  However, we observed a divergence in responses to applied sunflecks, where the two Acer species became induced more quickly than F. grandifolia and exhibited higher cumulative carbon assimilation when compared to conditions of constant saturating light.  This suggests the Acer species are well positioned to persist in the variable light environments of the forest understory.