Linking soils and streams during events: response of stream water K+
concentration to soil exchangeable K+ concentration in
small catchments with fragipan soils (Carpathian Foothills, Poland)
Abstract
The study aimed to determine the linkage between soil exchangeable
potassium (K+) concentration and stream water
K+ concentration during rainfall and snowmelt events.
The research was performed in small catchments with different land use
(i.e. woodland, traditional agriculture, experimental agriculture,
mixed-use) in the Carpathian Foothills (Poland). All of the studied
catchments whose hillslopes were covered with fragipan soils had a
markedly lower hydraulic conductivity (Ksat) in the
fragipan (Btx) than in the horizons lying above (A and E). These highly
permeable horizons determine the K+ influx to streams
during most event types except snowmelts with frozen soil. In the
woodland catchment, stream water K+ concentrations
during events are determined by a high vertical variability in Ksat and
exchangeable K+ concentrations in soil profiles. Rapid
flushing of K+ from the topsoil Ah horizon with higher
Ksat and higher exchangeable K+
concentrations than in the lying lower E horizon resulted in a clockwise
hysteresis of K+ in stream water during most events.
In the agricultural catchments, changes in stream water
K+ concentration during events were determined by
distinct differences between soil exchangeable K+
concentrations on hillslopes and in riparian areas. For example, during
rainfall events under dry antecedent conditions, exchangeable
K+ concentrations in topsoil horizons on hillslopes
were distinctly higher than concentrations of exchangeable
K+ in riparian area soils. The inflow of alluvial
water with a low dose of K+ before the inflow of
throughflow from hillslopes with a high dose of K+
thus resulted in wide counterclockwise hystereses for streamwater
K+.