RELATIONS AMONG REDOX POTENTIALS, WATER LEVELS, AND RIPARIAN VEGETATION

摘要

Oxidation-reduction potential (redox) integrates physical and biological conditions, and provides insights into biogeochemical processes occurring in subsurface environments. Although in situ redox data are often highly variable, patterns of variation may be examined to describe spatial and temporal heterogeneity in seasonally saturated habitats of riparian areas. In two montane meadows of northeast Oregon (elevation 1,320 m), we measured redox (E_h at 10- and 25-cm depths) and water table elevation in three herbaceous plant communities. The plant communities―dry, moist, and wet meadow types―occur over small-scale topographic and hydrologic gradients on the floodplain. Water table elevation followed seasonal patterns of stream discharge, being highest during spring snowmelt and lowest in late summer. Patterns of redox potential tracked the seasonal changes in water table elevation. Redox potential measurements were: (1) least variable in the terrace dry community at 10 cm, where soil conditions remained aerobic throughout the year (CV= 0.12; E_h values = 282 to 637 mV) and (2) most variable in the wet community at 25 cm, where soil conditions exhibited large microsite variability (CV = 4.39; E_h values = -195 to 524 mV). The distribution of meadow plant communities reflects the spatial and temporal heterogeneity of water levels and redox potentials.