Hydrological Separation of Event and Pre-event Soil Water in a Cultivated Landscape

Soil
water mixing is a complex process that is dependent on vegetation,
soil physiochemical characteristics, and climate. In this research,
we utilize natural tracers, δ18O and δ2H, to determine if hydrological separation of recent precipitation
event and pre-event water occurred within the soil profile of a maize
field in central Ohio. Soil samples were collected at three sites
and four depths, and the soil water was extracted via cryogenic distillation.
Soil water isotopic composition showed mixing of precipitation event
and pre-event water that reflected weighted average precipitation
isotopic composition. The range in isotopic signatures also indicated
that hydrological mixing within the soil profile was facilitated by
soil physical characteristics and effective gravitational drainage
of event water. These results support previous work that hydrological
separation does not occur in soil water in temperate climates and
contribute to ongoing research to conceptualize soil water cycling
in monoculture systems.