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University of Alberta (2000)

Modelling strategies of the soil plant atmosphere continuum in water limited environments and elevated atmospheric CO2

Manunta, Paolo

Titre : Modelling strategies of the soil plant atmosphere continuum in water limited environments and elevated atmospheric CO2

Auteur : Manunta, Paolo

Université de soutenance : University of Alberta

Grade : Doctor of Philosophy (Ph.D.) 2000

Résumé
Higher temperatures and changes in rainfall patterns have been forecasted for the future because of higher levels of carbon dioxide in the atmosphere. Warmer temperatures may cause an increase in evapotranspiration (ET) demand. A reduction in rainfall could heighten the severity and duration of drought in arid and semi-arid regions. This paper presented the water transfer scheme which includes water uptake by roots. It also described the interaction between ET and carbon dioxide enrichment. The predicted response of a plant canopy in relation to energy exchange processes was also tested for elevated atmospheric carbon dioxide level. Simulated and measured canopy conductances were reduced by about 30 per cent under elevated carbon dioxide under ideal water supply conditions. A 6 per cent reduction in both simulated and measured seasonal water use was observed under ideal conditions, while a 2 per cent reduction was observed under suboptimum irrigation. The modelling framework also included adaptation and functioning of root system of woody plant canopies. The hypothesis that water that has been relocated via hydraulic lift prevents the upper soil layers from becoming extremely dry was confirmed. Soil layers close to the surface were found to maintain soil water potential between -1.0 and -1.3 MPs during the drought period as well as under 2 different rainfall regimes. In contrast, the absence of hydraulic lift caused the soil layer close to the surface to drop to -20 MPa and -28 MPa. An additional amount of water for plant transpiration was not provided in any large amounts when water was relocated via hydraulic lift. It was concluded that carbon dioxide modelling and transpiration interactions may produce accurate estimates of canopy water use under the predicted climate change. Hydraulic lift was found to be more important for redistribution of soil moisture than for canopy transpiration

Mots clés  : ABSORPTION, CARBON COMPOUNDS, CARBON OXIDES, CHALCOGENIDES, CLIMATIC CHANGE, MATHEMATICAL MODELS, OXIDES, OXYGEN COMPOUNDS, SEPARATION PROCESSES, SORPTION, UPTAKE DEIAGRICULTURE, BIOLOGY, CANOPIES, CARBON DIOXIDE, CLIMATE MODELS, CLIMATIC CHANGE, ENVIRONMENT, GREENHOUSE EFFECT, PRECIPITATION, ROOT ABSORPTION, TRANSPIRATION

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Page publiée le 5 avril 2008, mise à jour le 29 octobre 2018