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ORIGINAL RESEARCH

Eco-Geophysical Imaging of Watershed-Scale Soil Patterns Links with Plant Community Spatial Patterns

^a Dep. of Geophysics, Stanford Univ., 397 Panama Mall, Stanford, CA 94305
^b Dep. of Plants, Soils and Climate, Utah State Univ., Old Main Hill, Logan, UT 84322
^c USDA-ARS, Northwest Watershed Research Center, 800 Park Blvd., Boise ID 83712
^d currently, Dep. of Food Production, Univ. of the West Indies, St Augustine, Trinidad and Tobago
^* Corresponding author (darearthscience{at}yahoo.com).

Received 19 June 2008.

The extent to which soil moisture and nutrient availability control the structure, function, and diversity of plant communities has aroused considerable interest 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 soil properties affecting resource pools, such as texture, are often poorly delineated at the landscape level. Traditional soil survey methods, developed for land evaluation, remain largely qualitative, based on the subjective analysis of the soil surveyor and often using vegetation patterns to demarcate soil boundaries. To date, no independent method of determining the properties of soil root-zone spatial patterns has been developed for use at the landscape scale, resulting in a knowledge gap between observed aboveground vegetation patterns and the distribution of belowground soil properties. The objective of this work was to determine whether a quantitative link could be observed between bulk soil electrical conductivity, used as an indicator of soil texture, and the plant community spatial pattern using geophysics. By comparing the geophysical signal with plant community patterns, we have discovered distinct vegetation niches corresponding to distinct zones of bulk soil electrical conductivity. A hierarchical ranking of the mean bulk soil electrical conductivity for each plant community type follows a power-law structure.

Abbreviations: CUAHSI, Consortium of Universities for the Advancement of Hydrological Sciences Inc. • ECa, bulk soil electrical conductivity • ECe, electrical conductivity of the soil solution extract • EMI, electromagnetic induction • G1, sparse grass communities • G2, dense grass communities • LAI, leaf area index • NEON, National Ecological Observation Network • S1, sparse mountain big sagebrush communities • S2, dense mountain big sagebrush communities • SB, snowbrush communities • VWC, volumetric water content