Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 1996
Publication Date: N/A
Interpretive Summary: The soil surface microclimate controls near-surface biological processes, including seedling germination, plant establishment, and insect population dynamics. The soil surface microclimate, characterized by soil temperature and water conditions, can be altered through management. Information concerning the effect of management alternatives on the surface microclimate could help land managers address the interactions between physical, chemical and biological factors impacted by management decisions, but this information is lacking. Models for plant growth and pest population dynamics exist, but in many cases can be greatly improved with better information about soil temperature and water conditions. Coupling these models with 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) mode simulates detailed heat and water movement in a plant-snow-residue-soil system. Based on results of a sensitivity analysis presented herein, the model was calibrated to a full year of data. The model was then validated using a second year of data. Comparison results between simulated and measured soil and moisture were very good. With the knowledge gained from this study, the SHAW model shows good potential for coupling with other models of physical or biological processes requiring accurate near-surface information. Such coupling could provide land managers with a powerful tool to address complicated interactions between the soil surface microclimate and physical and biological processes affected by management options.
Technical Abstract: 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 dn biological factors in the near surface, but lack the information necessary The ability to predict temperature and water within the soil-plant-residue- system, was applied to two full years of data on semiarid 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 the two years. Rapid changes in surface water potential and drying of the soil profile as simulated by the model closely tracked measured observations.