Soil Water Availability on MPG Ranch

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Soil Water Availability on MPG Ranch

December 12, 2013

Dan Mummey describes the deployment of soil moisture and air temperature sensors and data loggers at strategic research locations.

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Plant responses to precipitation vary with soil properties across the landscape. Soil structure and texture cause variation in site capacity for water uptake and retention over time. This variation alters spatial and temporal availability of water to plants and thus favors different water use strategies. Community composition follows this variation, making soil water availability an important analytical tool in understanding plant community structure.

Soil Moisture Sensor Locations

We deployed MPS-2 dielectric water potential sensors (Decagon Devices) at each site. MPS-2 sensors contain ceramic disks that equilibrate with soil water. MPS-2 sensors collect and transmit soil water potential and temperature data in real time. MPS-2 sensors should not require maintenance.A crew augered three holes at each location. Sensors were placed at 6 inch and 3 foot depths in two of the holes. The third hole supports a post to mount instrumentation. Sensor wires were buried 6 inches below the soil surface to avoid damage from large animals.

iButtons were placed in radiation shields designed and constructed by Zack Holden (USFS). Zack tested many shield designs and found this design worked best. Air temperature is measured at 5 foot height on all sites.

Soil samples were collected from four depths in each hole. Each sample will be analyzed for properties that influence soil hydrology. Information obtained from soils analysis will be integrated with climate and soils data to extrapolate soil water potential data to other areas.

Climate information helps delineate plant and animal habitat preferences. Unlike ranch areas west of Mt. Baldy, only coarse climate information is available for the boondocks. We deployed air temperature sensors at locations depicted by red dots on the map below. Sensors and radiation shields were mounted on the north side of trees.