Research Projects

Seedbed Microclimate: Modeling and Monitoring Soil Moisture in Support of the Restoration of Military Lands

PI: Todd Caldwell
Co-PI: Eric McDonald

Funded by: ITAM, Charis Corporation, Subcontract No. GS-012FG-A

Collaborators: Ruth Sparks and Matthew Hamilton, ITAM, Kent Osler, David Andersen, and Dennis Hansen, Bechtel-NV

Right: Soil probes in excavated soil pit

Keywords: restoration, Mojave, vadose zone, soil moisture, modeling, hydrology

Project Description

The National Training Center (NTC), the Army's primary mechanized maneuver training facility, covers approximately 2600 km 2 within the Mojave Desert in southern California, is the subject of ongoing studies to support the sustainability of military lands in desert environments. Restoration of these lands by the Integrated Training Areas Management (ITAM) Program requires the identification of optimum growing conditions to reestablish desert vegetation from seed and seedling, especially with regard to the timing and abundance of plant-available water. The reestablishment and growth of desert plants is largely limited by the availability of soil moisture. Thus, a practical and economical methodology to estimate available soil-moist is needed to facilitate revegetation practices under the extremely arid conditions that typically prevail.

Seedbed microclimate; soil-water content, soil-water potential, and soil temperature, were continuously monitored and used to calibrate the Simultaneous Heat And Water (SHAW) and HYDRUS numerical models at 3, large scale, seeded restoration sites. Models were hierarchically parameterized to varying degrees of field data and modeling complexity to determine output validity. Various surface treatments including ripping, tackifiers, straw mulch, gravel mulch and plastic sheeting, and several irrigation scenarios were evaluated to determine effective restoration practices in order to maximize revegetation success and minimize water use.

Moderate site characterization and soil-water balance modeling can provide significant knowledge of seedbed microclimate, thus maximizing the benefits of irrigation applications. Soil-moisture can be manipulated to the appropriate depths and times to facilitate both seed germination and root establishment when revegetating Mojave Desert sites. Lastly, the benefits of common restoration practices (mulches and surface preparation) are dependent on both soil properties and seasonal timing.

Below: Soil probes used for monitoring soil matric potential and water content installed horizontally into excavated soil pits prior to seed application and large scale irrigation.

Below: Completed soil moisture monitoring system installed on a restoration site at the NTC. Irrigation was supplied through numerous wobbler heads and monitored for seedbed microclimate.