MODELING PLANT CANOPY EFFECTS ON VARIABILITY OF SOIL-TEMPERATURE AND WATER

Vegetative cover affects the spatial and temporal variability of heat and water in the soil. The ability to predict temperature and water conditions enhances our ability to evaluate management options for soil and water conservation, plant establishment and pest control. The simultaneous heat and water (SHAW) model is a detailed process model of heat and water movement in a snow-residue-soil system. This paper describes provisions added to the SHAW model for vegetative cover and simulation of heat and water transfer through the soil-plant-air continuum. The model was applied without calibration to one full year of data on semiarid sagebrush rangeland to simulate vegetation effects on the spatial and temporal variability of soil temperature and water. The model currently has no provisions for plant growth or annual variation in leaf area index, resulting in insufficient shading of the soil surface during summer months. Nevertheless, the model accounted for over 96% of the variation in near-surface soil temperature for sagebrush-covered areas and over 91% of the variation for bare soil surfaces. Simulated water potential and total water use also agreed well with measured values.