Investigating the controls on greenhouse gas emission in the riparian zone of a small headwater catchment using an automated monitoring system

Abstract

Riparian zones as the transition zone between terrestrial and aquatic ecosystems play an important role in C and N cycling and greenhouse gas (GHG) emissions. As such, they may help to mitigate climate change but could also accelerate it, depending on the particular processes affected by changes in the hydrologic regime. Hydrological observations indicated frequent shallow groundwater in the riparian zone, especially near the stream and during the wet winter and spring seasons with consequently frequent occurrence of soil water saturation. The redox potential was mainly governed by the soil water regime: under water saturation conditions, the redox potential of the soil decreased and returned to the oxic state after soil drainage. We found that soil temperature and soil water content were the main drivers of the variations in CO2 fluxes, with highest CO2 emission during summer and the lowest emissions in the winter period (162.2–5.4 mg CO2–C m−2 h−1). The annual average daily N2O emission rate was low (2.3 μg N2O‐N m−2 h−1), with the highest average daily N2O emission in March as a result of low temperature and partial soil saturation after heavy precipitation events (37.5 μg N2O‐N m−2 h−1). Our study showed that continuous measurement of redox potential, soil temperature, and soil water content can improve the understanding of GHG emissions in riparian zones.

Investigation of Daily to Seasonal Variation in Greenhouse Gas Emission and Cycling in Agricultural Riparian Zone Soils

“…CH4 fluxes in a temperate forest in central Ontario, Canada showed uptake rates increasing with decreasing moisture content from June to September . This agrees with numerous studies demonstrating increased soil respiration rates (and CO2 emissions) in the summer (with higher temperatures and lower soil moisture content) compared to the colder and wetter months (Almagro et al, 2009;De Carlo et al, 2019;Amadi et al, 2016;Wang et al, 2021). In some cases, soil desiccation during summer droughts can limit the soil respiration process, where precipitation events would trigger a rapid rebound of respiration rates (Almagro et al, 2009;Vidon et al, 2014).…”

“…CO2 emissions and subsurface concentrations were high in late July before decreasing drastically in August. High soil temperatures paired with low soil moisture (to a certain limit), as seen in August, have been observed to increase soil respiration productivity (Almagro et al, 2009;De Carlo et al, 2019;Amadi et al, 2016;Wang et al, 2021). However, the moisture content in August may be low enough to be limiting and impede soil respiration, resulting in the decreasing trends in subsurface concentration and surface flux in the same month (Vidon et al, 2014).…”

Soil Acidification Vulnerability and Long-term Trace Metal Depletion Under Rubber Tree Plantations in the Semi-mountainous Region of West Côte d'Ivoire

“…Redox potential, a parameter that assesses the oxidation and reduction state of the soil, is influenced by water and soil weathering. Soil Eh range can be differentiated into oxic (>+400 mV), weakly reducing (+400 to +200 mV), moderately reducing (+200 to −100 mV), and strongly reducing (<−100 mV) conditions [18], [19]. Consequently, the edaphic environment of RT grown soils was weakly reducing while the one of the control fields varied from weakly to moderately reducing.…”