Effects of land-use practice on wetland soil hydrology, salinity, and biogeochemistry in the prairie pothole region

Land-use practice shift to short rotation willow (SRW) can accelerate vegetation linked alterations in the shallow groundwater table (GWT), salinity, and nutrient availability in the hydrologically dynamic wetland riparian zones. Additionally, SRW has higher potentials to sequester soil organic carbon (SOC) and can further impact greenhouse gas (GHG) emissions and extracellular enzyme activities (EEAs). In a field experiment, the effects of SRW were evaluated by measuring the depth to GWT; groundwater and soil electrical conductivity (EC), nutrients (N, P, K, and S), and SOC content with different fractions and chemical compositions in soils (60-cm depth) collected along transects during the first rotation (3-year cycle) and compared with adjacent annual crop (AC), and pasture (PA) in two (site A and B) semi-arid prairie pothole region (PPR) wetland systems. In a microcosm experiment, GHG (CO2, CH4, and N2O) emissions and EEAs [β-glucosidase (BG), N-acetyl glucosaminidase (NAG), and alkaline phosphatase (AP)] were measured in intact soil cores (30-cm depth) collected from the same field sites, and treated with declining water tables (2 to 26 cm depth), and salinity levels (S0 = control, S1 = 6 mS cm-1, and S2 = 12 mS cm-1). The GWT responded to precipitation patterns. Both groundwater and soil EC varied significantly (p 0.05) for depths, years, and months. Under SRW, soil NH4+-N and K+ contents were lower, whereas NO3--N, PO43--P, and SO42--S were higher. The groundwater NH4+-N, NO3--N, K+, and SO42--S were significantly higher (p 0.05) across land-uses. Total SOC was higher in PA in both sites, but significant (p SRW = AC). The SOC and water extractable organic carbon (WEOC) were significantly higher (p AC = SRW. Compared to control, emissions of CO2 and CH4 were significantly lower (p AC = SRW), suggested that the effects resulted from background SOC. Soil EEAs were significantly (p < 0.05) reduced under higher depth to GWT except reverse for BG in site B. However, they did not differ significantly among salinity treatments. This research demonstrates that land-use linked variation in GWT and salinity can have a consequential effect on the riparian wetland soil nutrients, SOC, GHG emissions, and EEAs in the PPR