Effects of vertical air temperature distribution within forest canopies on photosynthesis and transpiration

Abstract

This study examined whether accurately simulating vertical air temperature (AT) distribution within forest canopies is essential for predicting vertical photosynthesis and transpiration distribution using multilayer canopy models. Inspecting earlier observational studies that reported vertical AT distribution within forest canopies, we showed that the common vertical AT difference within forest canopies was lower than 3.0 °C. We showed, using a leaf-scale transpiration-photosynthesis model, that a 3. 0 °C AT difference caused smaller differences in leaf-scale photosynthesis and transpiration rates than a common vertical difference in photosynthetic active radiation (PAR) intensity within forest canopies when AT was higher than ca. 15 °C. While, the AT difference caused larger differences in leaf-scale photosynthetic and transpiration rates than the PAR difference when AT was lower than ca. 10 °C . However, the ranges in the rates with changing AT by 3.0 °C were comparable with predictability of a leaf-scale transpiration-photosynthesis model. Thus, we conclude that accurately simulating AT distribution is not essential at this stage for calculating vertical photosynthesis and transpiration distribution using multilayer canopy models.