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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #244194
Title: Geophysical imaging of watershed subsurface patterns and prediction of soil texture and water holding capacity

Author
item ABDU, H - Utah State University
item ROBINSON, D - Stanford University
item Seyfried, Mark
item JONES, S - Utah State University

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2008
Publication Date: 12/23/2008
Citation: Abdu, H., Robinson, D.A., Seyfried, M.S., Jones, S. 2008. Geophysical Imaging of Watershed Subsurface Patterns and Prediction of Soil Texture and Water Holding Capacity. Water Resources Research, 44, Wood 18, doi:10.1029/2008WR007043.

Interpretive Summary: Prediction of the impacts of global change on plant productivity (and carbon dynamics) is partly dependent on the distribution of soils on the landscape. Traditional methods of determining soil distribution require physical excavation so that surveys are typically limited to around 10 observations per day, depending on conditions, making detailed assessment of soil properties in relation to vegetation a difficult task. We investigated the use of a non-invasive electromagnetic induction (EMI) measurement system to facilitate determination of soil/vegetation relationships. The EMI system measures the bulk soil electrical conductivity, which is related to soil texture, water content and salt content and can make 10,000 measurements in a day. Our purpose was to investigate the linkage between above ground vegetation and below ground soil properties. We conducted our study on a small (41 ha) watershed in the Reynolds Creek Experimental Watershed in Idaho. The watershed is highly heterogeneous with respect to vegetation, ranging from stands of fir and aspen to rocky outcrops. We were able to demonstrate a strong correlation between above ground vegetation type and below ground water content and texture. Thus, in this environment, vegetation distribution appears to be related to soil water content and soil texture, which can be mapped with the EMI system. We are currently following with detailed modeling of soil water dynamics to extend these results.

Technical Abstract: The extent to which soil resource availability, nutrients or moisture, contro1 the structure, function and diversity of plant communities has aroused considerableinterest in the past decade, and remains topical in light of global change. Numerous plant communities are controlled either by water or soil nutrient availability, and yet spatial patterns of subsurface resources are poorly delineated or understood. As a consequence, our understanding and interpretation of patterns and species richness is often biased toward above ground observation, or surrogate measures of soil resources, one of which is mean annual precipitation (MAP) in the case of soil water content. We report on the use of geophysical spatial imaging, in a small semi arid watershed (41 ha), as a non-invasive method of identifying and quantifying soil root-zone properties related to clay% and water content. The electrical signal from the soil, when analyzed, is used to identify and delineate soil spatial properties,which are seen here to relate to observed, above-ground, plant community patterns in the watershed.