Abstract
We used a multi-layer model to analyse the impact of leaf physiology on the diurnal, seasonal, and inter-annual fluctuations in gas exchange in a warm-temperate evergreen broad-leaved forest in Japan. The influences of physiological parameters at the single leaf scale on the canopy scale gas exchange were investigated, including normalised dark respiration rate, R nleaf25, normalised maximum carboxylation rate, V cmax25, and the stomatal coefficient, m, of an improved ball-type stomatal conductance model. Simulated sensible and latent heat fluxes and CO 2 flux at the canopy roughly reproduced the amplitude and diurnal and seasonal fluctuations in the observed fluxes, with the constant m and one set of reference V cmax and R nleaf with their temperature dependences. Overestimations of latent heat flux and thus underestimation of sensible heat flux with a constant m demonstrated that additional stomatal closure should be expected during a drought period. Overestimation of CO 2 flux during the leaf expansion period and the severe drought period with changing m values related to soil moisture conditions demonstrated that the decline in canopy scale CO 2 uptake during these periods was related to some physiological restraints, other than simple uniform stomatal closure, at the single leaf scale.
Published Version
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