Land Use and Soil Type Impacts on Soil Moisture and Multi-Level Soil Temperature Measurements for the North Carolina ECONet

Soil moisture and soil temperature are critical to understanding agricultural processes as well as monitoring drought conditions. North Carolina has complex soil topographies, with clay based soils in much of western NC and sandy soils in eastern NC.  While soil moisture and soil temperature are dependent on geographic factors such as latitude, elevation, and topography, land use and land cover also play a role.

The State Climate Office (SCO) of NC maintains and operates the North Carolina Environment and Climate Observing Network (NC ECONet).  This network measures soil moisture and soil temperature at 40 stations across North Carolina.  Each station has unique geography affording the ability to compare and contrast a variety of soil and land cover types.  Measurements of soil moisture are obtained at 20 cm using a ML3 theta probe by Delta-T devices. Soil temperature is measured two different ways: at 10cm using the Campbell Scientific CS-107 thermistor and at 4 depths: 10cm, 20cm, 30cm, 40cm using an experimental multi-depth soil temperature profiler developed at the SCO.

Preliminary results indicate that similar soil types at different locations show comparable responses to moisture, but the land use impacts the rate at which water percolates through the soil layer. Overall, the experimental multi-depth soil temperature probe’s signal is within 3% at the 10cm level of the single level probe. The differences are larger in clay soils than in sandy soils. Additionally, soil texture impacts the diurnal temperature curves more in sandy soils than in clay soils.

These data are routinely used by researchers and a better understanding of the impacts of land-surface properties on subsurface measurements can improve land use models and short-term forecasts. Also, an expansion of the network across the entire state would further enhance decision maker’s abilities in monitoring and forecasting drought conditions.