Crown architecture, light interception, and stomatal conductance patterns for sympatric deciduous and evergreen species in a forest understory

Abstract

Within a mixed deciduous forest in central Virginia, daily patterns of light interception and stomatal conductance were related to crown architecture for the deciduous Asimina triloba and the evergreen Ilex opaca. For A. triloba, branches were up to 54% longer, the bifurcation ratio was 15% lower, branch internode lengths were 15% greater, and leaf angles were closer to the horizontal plane (9 vs. 22°) than for I. opaca, possibly contributing to a greater percentage of sunlit leaves for A. triloba at 1100 and 1400 (22.4 vs. 10.0 and 30.0 vs. 10.1%, respectively). Maximum stomatal conductances to water vapor diffusion were 4.0 and 4.6 mm∙s−1 for sunlit leaves of A. triloba and I. opaca, respectively. Sunlit and shaded leaf stomatal conductances were similar in A. triloba throughout the day, but in I. opaca, values for sunlit leaves were up to 1.3 mm∙s−1 greater than values measured in shaded leaves. In addition, stomatal conductances for shaded leaves of A. triloba remained approximately 1.0 mm∙s−1 greater than for I. opaca throughout most of the afternoon. Therefore, within a forest understory environment, sympatric deciduous and evergreen species may differ in crown architecture, light interception, and stomatal conductance patterns.