A modified Jarvis–Stewart model of canopy transpiration (E_c) was tested over five ecosystems differing in climate, soil type and species composition. The aims of this study were to investigate the model's applicability over multiple ecosystems; to determine whether the number of model parameters could be reduced by assuming that site-specific responses of E_c to solar radiation, vapour pressure deficit and soil moisture content vary little between sites; and to examine convergence of behaviour of canopy water-use across multiple sites. This was accomplished by the following: (i) calibrating the model for each site to determine a set of site-specific (SS) parameters, and (ii) calibrating the model for all sites simultaneously to determine a set of combined sites (CS) parameters. The performance of both models was compared with measured E_c data and a statistical benchmark using an artificial neural network (ANN). Both the CS and SS models performed well, explaining hourly and daily variation in E_c. The SS model produced slightly better model statistics [R² = 0.75–0.91; model efficiency (ME) = 0.53–0.81; root mean square error (RMSE) = 0.0015–0.0280 mm h^-1] than the CS model (R² = 0.68–0.87; ME = 0.45–0.72; RMSE = 0.0023–0.0164 mm h^-1). Both were highly comparable with the ANN (R² = 0.77–0.90; ME = 0.58–0.80; RMSE = 0.0007–0.0122 mm h^-1). These results indicate that the response of canopy water-use to abiotic drivers displayed significant convergence across sites, but the absolute magnitude of E_c was site specific. Period totals estimated with the modified Jarvis–Stewart model provided close approximations of observed totals, demonstrating the effectiveness of this model as a tool aiding water resource management. Analysis of the measured diel patterns of water use revealed significant nocturnal transpiration (9–18% of total water use by the canopy), but no Jarvis–Stewart formulations are able to capture this because of the dependence of water-use on solar radiation, which is zero at night.

Item Type:	Refereed Article
Keywords:	transpiration, Jarvis-Stewart model, tree water-use, functional convergence
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Forestry sciences
Research Field:	Tree nutrition and physiology
Objective Division:	Environmental Management
Objective Group:	Fresh, ground and surface water systems and management
Objective Field:	Assessment and management of freshwater ecosystems
UTAS Author:	O'Grady, AP (Dr Anthony O'Grady)
ID Code:	116650
Year Published:	2013
Web of Science® Times Cited:	51
Deposited By:	Plant Science
Deposited On:	2017-05-16
Last Modified:	2017-10-17
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