Abstract Introduction Channel incision can disconnect streams from their floodplains, potentially depleting carbon (C) in riparian soils by stimulating microbial decomposition. Stream restoration may offer an opportunity to replenish soil C pools by saturating riparian soils with water and slowing microbial activity. Objectives Assess how stream restoration affects soil C persistence and greenhouse gas emissions in riparian soils. Methods We measured soil C pools and methane (CH 4 , a strong greenhouse gas) emissions adjacent to stream reaches restored with plug‐and‐ponds or beaver dam analogs (BDAs) in northern New Mexico. We also measured mineral‐associated organic carbon (a persistent C pool) and particulate organic matter (particulate organic C POC, a more labile C pool) as indicators of soil C persistence and their isotopic composition to inform formation pathways. Results Plug‐and‐ponds increased POC from 22.3 ± 2.34 g C/kg to 62.5 ± 9.71 g C/kg within 3 years, with increases in soil moisture and decreases in δ 13 C together suggesting suppression of microbial decomposition. While plug‐and‐ponds also increased CH 4 emissions (from 0.14 ± 0.055 μg C m −2 s −1 to 1.73 ± 0.93 μg C m −2 s −1 ), preliminary calculations suggest that this did not offset the climate benefit of increased POC. BDAs did not consistently increase soil C or soil moisture; steeper slopes at the BDA sites may have prevented water saturation that is necessary to slow microbial decomposition. Conclusions Stream restoration efforts can increase soil C accumulation enough to offset increased CH 4 emissions, but success depends on initial site characteristics, like slope.
Krichels et al. (Tue,) studied this question.