Leaf optical responses to light and soil nutrient availability in temperate deciduous trees

Leaf optical parameters influence light availability at the cellular, leaf, and canopy scale of integration. While recent studies have focused on leaf optical responses to acute plant stress, the effects of changes in plant resources on leaf optics remain poorly characterized. We examined leaf optical and anatomical responses of five temperate deciduous tree species to moderate changes in nutrient and light availability. Spectral reflectance in the visible waveband generally increased at high light, but decreased with increased nutrient availability. Patterns of both spectral reflectance and absorptance were primarily determined by chlorophyll concentration although carotenoid concentration was also influential. While most anatomical features did not explain residual variation in reflectance, cuticle thickness was significantly related to reflectance at complementary angles compared to the angle of incidence. Absorptance did not change with light environment; however, absorption efficiency per unit biomass increased by approximately 40% under low light, due to reduced leaf mass per area. We conclude that changes in resource availability differentially influence leaf optical properties and that such changes are driven primarily by changes in pigment concentrations. The magnitude of leaf optical responses to moderate changes in resource availability was comparable to those of acute stress responses and varied among species.