A Canopy Transpiration Model Based on Scaling Up Stomatal Conductance and Radiation Interception as Affected by Leaf Area Index
| Autor: | Nigel W. M. Warwick, Muhammad Shahinur Alam, David Lamb |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Canopy
Stomatal conductance lcsh:Hydraulic engineering 010504 meteorology & atmospheric sciences Geography Planning and Development Aquatic Science Atmospheric sciences 01 natural sciences Biochemistry transpiration modelling lcsh:Water supply for domestic and industrial purposes lcsh:TC1-978 Evapotranspiration Leaf area index 0105 earth and related environmental sciences Water Science and Technology Transpiration lcsh:TD201-500 04 agricultural and veterinary sciences Canopy conductance LAI pasture Photosynthetically active radiation stomatal conductance 040103 agronomy & agriculture fAPAR 0401 agriculture forestry and fisheries Environmental science Interception |
| Zdroj: | Water Volume 13 Issue 3 Water, Vol 13, Iss 252, p 252 (2021) |
| ISSN: | 2073-4441 |
| DOI: | 10.3390/w13030252 |
| Popis: | Estimating transpiration as an individual component of canopy evapotranspiration using a theoretical approach is extremely useful as it eliminates the complexity involved in partitioning evapotranspiration. A model to predict transpiration based on radiation intercepted at various levels of canopy leaf area index (LAI) was developed in a controlled environment using a pasture species, tall fescue (Festuca arundinacea var. Demeter). The canopy was assumed to be a composite of two indistinct layers defined as sunlit and shaded the proportion of which was calculated by utilizing a weighted model (W model). The radiation energy utilized by each layer was calculated from the PAR at the top of the canopy and the fraction of absorbed photosynthetically active radiation (fAPAR) corresponding to the LAI of the sunlit and shaded layers. A relationship between LAI and fAPAR was also established for this specific canopy to aid the calculation of energy interception. Canopy conductance was estimated from scaling up of stomatal conductance measured at the individual leaf level. Other environmental factors that drive transpiration were monitored accordingly for each individual layer. The Penman&ndash Monteith and Jarvis evapotranspiration models were used as the basis to construct a modified transpiration model suitable for controlled environment conditions. Specially, constructed self-watering tubs were used to measure actual transpiration to validate the model output. The model provided good agreement of measured transpiration (actual transpiration = 0.96 × calculated transpiration, R2 = 0.98 p < 0.001) with the predicted values. This was particularly so at lower LAIs. Probable reasons for the discrepancy at higher LAI are explained. Both the predicted and experimental transpiration varied from 0.21 to 0.56 mm h&minus 1 for the range of available LAIs. The physical proportion of the shaded layer exceeded that of the sunlit layer near LAI of 3.0, however, the contribution of the sunlit layer to the total transpiration remains higher throughout the entire growing season. |
| Databáze: | OpenAIRE |
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