Hydric Soils in a Southeastern Oregon Vernal Pool
- David Clausnitzer *a,
- J. Herbert Huddlestonb,
- Edward Hornc,
- Mark Kellerd and
- Curtis Leete
- a USGS-FRESC, 3200 Jefferson Way, Corvallis, OR 97331
b Dep. of Crop and Soil Sciences, Oregon State University, Corvallis, OR 97331
c Prineville Office, Bureau of Land Management, 3050 NE Third Street, Prineville, OR 97754
d Burns Office, NRCS, HC 74, 12858 Highway 20 W., Hines, OR 97738
e Burns Office, Bureau of Land Management, HC 74, 12533 Highway 20 W., Hines, OR 97738
Vernal pools on the High Lava Plain of the northern Great Basin become ponded in most years, but their soils exhibit weak redoximorphic features indicative of hydric conditions. We studied the hydrology, temperature, redox potentials, soil chemistry, and soil morphology of a vernal pool to determine if the soils are hydric, and to evaluate hydric soil field indicators. We collected data for 3 yr from piezometers, Pt electrodes, and thermocouples. Soil and water samples were analyzed for pH, organic C, and extractable Fe and Mn. Soils were ponded from January through April or May, but subsurface saturation was never detected. Soil temperatures 50 cm below the surface rose above 5°C by March. Clayey Bt horizons perched water and limited saturation to the upper 10 cm. Redox potentials at a 5-cm depth were often between 200 and 300 mV, indicating anaerobic conditions, but producing soluble Fe2+ concentrations <1 mg L−1 Extractable soil Fe contents indicated Fe depletion from pool surface horizons and accumulation at or near the upper Bt1 horizon. Depletions and concentrations did not satisfy the criteria of any current hydric soil indicators. We recommend development of new indicators based on acceptance of fewer, less distinct redox concentrations for recognition of a depleted A horizon, and on presence of a thin zone containing redox concentrations located in the upper part of the near-surface perching horizon.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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