Solute Fluxes Through Restored Prairie and Intensively Managed Critical Zones in Nebraska and Iowa

Abstract

Agricultural activities in the Midwestern United States have potentially altered geochemical fluxes within the critical zone (CZ) compared to native prairie systems that previously dominated the region. To quantify the impact of agricultural land use on soil and stream solute behavior, we are studying two watersheds in the region: Glacier Creek Preserve (GCP) in eastern Nebraska and the Intensively Managed Landscapes Critical Zone Observatory (IML-CZO) in eastern Iowa. Both watersheds were initially under agricultural land use for over 100 years, but part of each watershed was restored to prairie 20 -50 years ago. Soils at both sites formed in thick Peoria loess (≥6 m) overlying glacial till with similar mean annual temperatures (∼10 • C) but slightly higher mean annual precipitation in Iowa (89 cm) compared to Nebraska (78 cm). At both sites, soil pore water and precipitation were collected every 2-4 weeks to measure anions, cations, and alkalinity; stream waters draining either restored prairie or agriculture were sampled similarly in Nebraska. Both soil moisture content and electrical conductivity were consistently higher in the upper one meter of agricultural soils compared to prairie soils in Nebraska, implying slower drainage and higher solute concentrations in the agricultural soils. At both sites, soil pore water Ca 2+ and Mg 2+ concentrations and annual fluxes were significantly higher in agricultural soils compared to restored prairie. Conversely, streams draining restored prairie have significantly higher Ca 2+ and Mg 2+ concentrations than the agricultural streams. Fluxes from agricultural streams, however, were higher than the prairie, pointing to a potential dilution effect of runoff from the agricultural land use. These observations lead to a conceptual model where deeply infiltrating water in restored prairie soils interacts with minerals present deeper in the soil before reaching the stream whereas in agricultural soils water does not infiltrate as deeply and thus experiences more shallow flowpaths to the stream. Furthermore, changes in geochemical and hydrologic fluxes have been realized in just a few decades since switching land use from agriculture to prairie. Thus, intensive agricultural land use may alter soil function and solute transport to streams compared to critical zones hosting tallgrass prairie vegetation.

Soil–vegetation–water interactions controlling solute flow and chemical weathering in volcanic ash soils of the high Andes

“…Suction cup samplers were installed between November and December 2018, and soil porewater samples were analyzed over the period from April 2019 to March 2020. This left ample time for the porous cups to equilibrate with the soil conditions (Dere et al, 2019). Soil porewater was collected biweekly, and a vacuum of 45-50 kPa was applied after every collection.…”

“…All solute concentrations are reported (mg L −1 ). We removed outliers by eliminating concentrations larger (smaller) than 2 standard deviations above (below) the average (Dere et al, 2019). The charge balance error (CBE) was calculated for each available sampling time.…”

Soil-vegetation-water interactions controlling solute flow and transport in volcanic ash soils of the high Andes

“…pore water samples were analyzed over the period from April 2019 to March 2020. This left ample time for the porous cups to equilibrate with the soil conditions (Dere et al, 2019). Soil pore water was collected biweekly and a vacuum of 45-50 kPa was applied after every collection.…”

“…All solute concentrations are reported in mg L -1 . We removed outliers by eliminating concentrations larger (smaller) than two standard deviations above (below) the average (Dere et al, 2019). The charge balance error (CBE) was calculated for each available sampling time.…”

Assessment of fall season habitat and coverboard use by snakes in a restored tallgrass prairie community

“…The reconstructed prairie is managed with a 3-year prescribed fire return interval that occurs in mid-spring, where no more than 2 of the 5 units are burned in one year. Additional details about the site can be found in Bragg et al (2016), Dere et al (2019), andManning et al (2022).…”