Date of this Version
Published in Micrometeorology in Agricultural Systems (2005) Agronomy Monograph no. 47: 131-154
Climatic conditions on the earth’s surface are in part a function of varying physical position (elevation, latitude, and aspect) and the influence of large-scale meteorological forces such as air and ocean currents. The density and architecture of plant canopies in natural systems are directly influenced by these climatic factors. By contrast, for agricultural systems, it is the crop canopies that often influence local microclimate. In both instances, the soil plays an important role in affecting climate near the surface. Properties of the surface soil layer including color, water content, texture, and density affect the partitioning of incident radiation and how much energy is used to evaporate water, warm the air above the ground, or warm the soil.
The amount of thermal energy that moves through an area of soil in a unit of time is the soil heat flux or heat flux density. The ability of a soil to conduct heat determines how fast its temperature changes during a day or between seasons. Soil temperature is a key factor affecting the rate of chemical and biological processes in the soil essential to plant growth. Soil heat flux is important in micrometeorology because it effectively couples energy transfer processes at the surface (surface energy balance) with energy transfer processes in the soil (soil thermal regime). This interaction between surface and subsurface energy transfer processes has led to detailed investigations of soil heat flux for a wide variety of agricultural systems.