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Clarifying the mechanisms that control variability in the spatial distribution of soil organic carbon (SOC) is key to accurate estimates of soil C fluxes. Mobile organic C (MOC), here defined as the fraction of SOC that is not strongly bound to mineral surfaces but that can be transported hydrologically as dissolved or particulate organic C, represents the portion of SOC whose residence time can be modulated via movement down profiles and across landscapes. The relationship between the spatial arrangement and turnover time of SOC is especially evident in the widely observed correlation between soil depth and mean residence time; deeper SOC tends to persist for relatively long periods in the profile.  Moisture can promote microbial mineralization of SOC to CO2, but water also can transport MOC throughout profiles and landscapes. Controls on the movement of MOC have not been fully elucidated however, and the relationship between MOC and the spatial arrangement of SOC has not been thoroughly explored. Using data collected from five distinct ecosystem types across North America we evaluate the hypothesis that moisture dynamics throughout the soil profile as driven by seasonality, vegetation productivity, and topographical position influence the spatial distribution of MOC, and thus the observed heterogeneity of SOC and its persistence. We demonstrate that, in soils with surplus water availability and structural features that permit sufficient flow, transport drives the accumulation of disproportionately large concentrations of MOC deep in the profile and in downslope topographical positions. Our results further demonstrate that the vertical and lateral transport of MOC is also regulated by variation between energy- and water-limited systems in the amount of seasonally-available water moving through the profile: at times and in places where relatively more surplus water is available, MOC is more readily translocated. Excursions from these patterns of transport and accumulation result from soil textural and structural characteristics that immobilize organic C or inhibit flow. These findings reveal the nuances of how soil moisture dynamics regulate vertical and lateral distributions of MOC, thereby promoting the development of heterogeneous SOC stores as well as deep, relatively persistent SOC pools.