Modelling plant canopy effects on variability of soil temperature and water: Model calibration and validation

Temperature conditions and the availability of moisture in the near-surface soil environment drives many important plant and other biological processes. Vegetation, which can be controlled by management, affects the spatial and temporal variability of heat and water in the soil. Land managers need to address the interactions between physical, chemical and biological factors in the near surface, but lack the necessary information. The ability to predict temperature and water within the soil-plant-atmosphere system enhances our ability to evaluate management options and enables better understanding of interactions between surface processes and the atmosphere. The Simultaneous Heat and Water (SHAW) Model, a detailed model of heat and water movement in a plant-snow-residue-soil system, was applied to 2 full years of data on semi-arid sagebrush rangeland to simulate vegetation effects on the spatial and temporal variation of soil temperature and water. Minor calibration was necessary to match the drop in measured soil water potential as the soil dried in the late spring and early summer. The model accounted for over 93% of the variation in average daily soil temperature for a sagebrush-covered area and over 96% of the variation in temperature for a bare soil surface for 2 years. Rapid changes in surface water potential and drying of the soil profile as simulated by the model closely tracked measured observations. (C) 1997 Academic Press Limited.