Riparian vegetation influences aquatic greenhouse gas production in an agricultural landscape

Abstract

Although riparian vegetation is widely acknowledged for its positive impact on soil and water quality and its role in regulating terrestrial greenhouse gas emissions in agricultural landscapes, there remains a gap in understanding how different types of riparian vegetation affect aquatic greenhouse gas production. Thus, the objective of this study was to investigate whether the type of vegetation within riparian zones influenced aquatic environmental factors, subsequently impacting aquatic greenhouse gas emissions. To address this, we measured greenhouse gases in the aquatic environment bordered by riparian zones with herbaceous vegetation (GRS) compared to undisturbed natural riparian forests dominated by deciduous (UNF-D) or coniferous (UNF-C) vegetation or a rehabilitated riparian forest (RH). Our findings indicate that aquatic CO₂ concentrations were not influenced (p < 0.05) by vegetation type ranging from 9 g L⁻¹ to 11 g L⁻¹. In contrast, aquatic CH₄ concentrations were significantly lower (p < 0.05) in treed riparian zones, ranging from 14 μg L⁻¹ to 24 μg L⁻¹, compared to a riparian zone with herbaceous vegetation (34 μg L⁻¹). However, we observed significantly higher (p < 0.05) aquatic N₂O concentrations in treed riparian zones (9.5 μg L⁻¹ to 10.3 μg L⁻¹), particularly those dominated by coniferous vegetation (23.0 μg L⁻¹), compared to the riparian zone with herbaceous vegetation (7.7 μg L⁻¹). The total CO₂-C equivalent (i.e., CO₂ + CH₄ + N₂O) was highest in the riparian zone with coniferous trees (UNF-C: 10,717 mg CO₂-Ceq L⁻¹), followed by the GRS (9494 mg CO₂-Ceq L⁻¹), RH (9423 mg CO₂-Ceq L⁻¹) and UNF-D (9,183 mg CO₂-Ceq L⁻¹) riparian zone. Moreover, riparian vegetation was influenced by various environmental factors that likely controlled physicochemical and biological processes related to the production of greenhouse gases within the aquatic environment.