Abstract
Land-use practices can alter shallow groundwater and salinity, further impacting greenhouse gas (GHG) emissions, particularly in the hydrologically dynamic riparian zones of wetlands. Emissions of CO2, CH4, and N2O were estimated in soil cores collected from two prairie pothole region (PPR) sites with three adjacent land-use practices (i.e., annual crop = AC, pasture = PA, and short rotation willow = SRW) and treated with declining water table depths (2 to 26 cm), and salinity (S0 = control, S1 = 6 mS cm−1, and S2 = 12 mS cm−1) in a microcosm experiment. Land-use practices significantly (p < 0.001) affected GHG emissions in soils from both sites in the order of PA > AC = SRW. Compared to the control, emissions of CO2 and CH4 were significantly lower under higher salinity treatments (i.e., S1 and S2), while N2O was significantly higher (p < 0.05). Emissions under declining groundwater table depths were significantly (p < 0.001) variable and specific to each gas, indicating the impacts of shifted soil moisture regime. Overall, the CO2 and CH4 emissions increased up to week four and then decreased with declining water table depths, whereas N2O emission increased up to a maximum at week six. The soils from SRW had considerably lower global warming potential compared to AC and PA. Groundwater salinity in soils from contrasting land-use in the PPR has significant impacts on GHG emissions with potential for crucial climate feedback; however, the magnitude and direction of the impacts depend on hydrology.
Highlights
CO2 emissions were significantly affected by contrasting land-use practices, suggesting that land-use was a significant driver of CO2 emission by influencing the heterotrophic respiration of soil organic carbon (SOC) (Oertel et al 2016)
The highest mean and cumulative CO2 emissions in our experiment was seen from pasture treatment (PA) soils, followed by AC and short rotation willow (SRW), respectively
Enrichment of SOC can trigger microbial activities that result in the emission of CO2, CH4, N2O; microbial activities are themselves subject to various proximal and distal drivers in soil (Oertel et al 2016)
Summary
Have minimal CH4 production because this practice promotes aerobic conditions that do not favor methanogenesis (Smith et al 2003). The effects of salinity on GHG emissions associated with a land-use change (Martin & Moseman-Valtierra 2015; Sheng et al 2015), or depth to the GWT (Ardón et al 2018; Mander et al 2011) have been studied, albeit mainly in coastal wetlands. Studies on the combined effects of GWT and salinity on GHG emissions under contrasting landuse practices within mineral wetlands in the PPR are scarce.
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