Transpiration from an Amazonian rainforest calculated from stomatal conductance measurements.
2017
ROBERTS, J. | CABRAL, O. M. R. | FISCH, G. | MOLION, L. C. B. | MOORE, C. J. | SHUTTLEWORTH, W. J.
A multi-layer combination equation has been used to calculate transpiration from a tropical rainforest in the central Amazon, Brazil. The five-layer formulation used through-canopy measurements of temperature and humidity deficit with leaf stomatal and boundary layer conductances scaled up to canopy layer values used a profile of canopy leaf area index derived from the literature. Net radiation input to each layer values was estimated from an above canopy measurement using an extinction function and leaf area index. Transpiration calculated for hourly and daily periods in a range of seasonal condition agreed well with those measured directly with and eddy correlation device. Four simplified forms of the transpiration calculation were also compared with the direct measurement. These simplified forms used the above-canopy or the average of the through-canopy values of weather variables and use either the average of leaf conductances multiplied by total leaf area index or the average of the layer conductances. These simplified forms of the tanspirations calculation gave poorer agreement with measured transpiration.
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