Group members preparing summary: Jared Anderson, Don Miller and Bobbier JohnsonUnit Summary:
Both global and regional climate models need accurate input/output of energy transformations to perform properly. Soil-vegetative-atmosphere transfer models (SVATs) link global and regional climate models to these fluxes. SVATs have emerged due to:
1. heat and moisture input to the atmosphere from the surface and how the surface takes these fluxes to make energy and momentum through friction.
2. the need to determine how plants and plant communities respond to environmental conditions.The SiB model allows for the interactions between plants and the atmosphere through:
1. Radiation absorption and reflection.
2. Control of evapotranspiration through plant stomates and canopies.
3. Momentum transfer by friction and turbulence caused by plants.
4. Soil moisture availability as a function of root length.
5. Insulation from plants shading of the surface.Terms are defined for plant and surface properties that affect atmospheric conditions as described by the SiB model. The areas affected are:
1. Atmospheric boundary conditions including temperature, vapor pressure, wind speed, radiation and precipitation.
2. Morphological parameters such as the two classifications of vegetation, and rooting zones.SVAT models are designed to describe the flow of energy, mass, momentum, trace gases, etc., between the atmosphere and the surface biosphere, all per unit time. Such flows are called fluxes, and the components are analogous to the potential, resistance, and current flow (flux) in an electric circuit. Stomates, which regulate plant water vapor and CO2 exchange, act as control valves, determining the flux of these gases between plants and the atmosphere. Equations are given describing conservation of energy and water substance and their interrelationship, allowing SVATs to describe both energy and moisture content in atmosphere and soil reservoirs, and their respective fluxes.
Dialog Summary:
Bernard - questions whether plants can sufficiently cool themselves if global warming causes the stomates to constrict, allowing less water for evaporative cooling.
Frundle - says alfalfa roots are not deep but are massive, drawing lots of surface moisture but not much deep moisture. Believes leaf area has a greater effect due to more stomata meaning greater water vapor release. Research shows greater CO2 concentrations cause smaller stomates but higher plant productivity.
Bickert - says that if stomates control CO2 exchange then root systems do not matter.
Kochen - does more transpiration change local weather conditions? Questions increased erosion with increased rainfall and atmospheric moisture content.
Johnson - provides reference for rooting depths of plants and points out the distinction between the amount of moisture in the soil and the amount actually available to plants, based on different soil types.
Salem - more roots mean more water transferred from soil through roots to the air.
Kardell - increased available moisture in the atmosphere from plant sources can be expected to increase the number and severity of thunderstorms and other types of severe weather.
Cillo - more plants growing puts more moisture into the atmosphere as evidenced by more rain in early summer than in late summer.
Pederson - Longer roots mean better chance of survival for plants, especially in drought conditions.
Anderson - deeper roots absorb more moisture and the plant puts more moisture into the air as a consequence.
Johnson - provides a website describing root depths for various plants, including corn at rooting depths of 3 to 4 feet.