The effects of land use and cover changes on lateral carbon losses from an ungagged headwater basin on the Chinese Loess Plateau

Modeling of lateral carbon movement is critical for investigating carbon cycle in inland waters, but it is quite challenging especially in headwater regions due mainly to the shortage of observations. In this study, long-term soil and carbon losses documented by sediment deposition before check dam were firstly integrated to the widely-used Soil and Water Assessment Toll (SWAT) for investigating the lateral movement of soil and carbon in a typical ungagged headwater basin on the Chinese Loess Plateau (CLP). Then, the effects of land use and land cover (LULC) changes on soil and carbon losses in the typical Loess watershed, Fangta River Basin (FTRB), were investigated. Our case study suggested that sediment and carbon fluxes documented by sediment records could provide key information for model calibration and validation in ungagged headwater regions, and the satisfactory performance suggested the promising use of sediment records in modeling of lateral carbon movement. Headwater regions on the CLP suffered serious soil and carbon losses during the past decades, and soil and carbon loss intensities were 6,821.6 t⋅km⁻²⋅yr⁻¹ and 16.9 t⋅km⁻²⋅yr⁻¹ during the study period (1976–2016), respectively. LULC changes characterized by conversion from cropland to forest, reversed the deterioration of soil and carbon losses caused by climate change. Our study identified the integration of sediment records and hydrological model in soil and lateral carbon movement investigation under dramatic environmental changes.