Salt marshes provide vital ecosystem services, including coastal protection and carbon sequestration. Roots play a key role in delivering these ecosystem services, as they stabilize soils and contribute to organic carbon accumulation. This study examines the impact of an experimental 3C temperature increase in a temperate salt marsh on belowground biomass dynamics across three elevation zones (pioneer zone, low marsh, and high marsh) and two temperature treatments (ambient, + 3°C) over a period of 3 yr (2019–2021). The elevation zones reflect different hydrological conditions. We found minimal effects of warming on belowground biomass, except in the high marsh during 2019, where drought and warming caused a shift to deeper rooting depths (- 53 +/- 19% in the upper soil depth, + 272 +/- 129% in the lower soil depth). Overall, root biomass was lowest in the high marsh (72.0 +/- 94.5 g m2) and highest in the low marsh (360.2 +/- 174.7 g m2), followed by the pioneer zone (218.7 +/- 233.8 g m2). In all years, root biomass peaked in summer (248.5 +/- 235.5 g m2) after rising from spring (181.4 +/- 183.4 g m2) and declining in autumn (216.5 +/- 209.4 g m2). Our findings suggest that a temperature increase of + 3°C above ambient temperatures has a marginal impact on root biomass dynamics, indicating that soil-stabilizing functions and belowground contributions to carbon sequestration may remain intact under global warming. Moreover, interactions between tidal regime and interannual precipitation patterns seem to play a more important role for root biomass variations.