Dry season assessment of carbon storage and emission from upland and riparian soils in the Ganga River basin

Soil organic carbon (C) and nitrogen (N) are profoundly affected by changes in land use and land cover (LULC), especially by farming in riparian zones. The five LULC classes were selected in contiguous order, i.e., undisturbed forest (CAL_ref), conventional agriculture lands (CAL), reservoir riparian zones (RSRZ), river riparian zones (RRZ), and undisturbed riparian zones (RZ_ref) in the Ganga River basin to study the C storage and emission trends at a landscape scale. The riparian soils showed higher moisture, temperature, and bulk density than the upland soils, strongly determining the spatial variations in the CO₂ equivalent (CO₂e), C:N ratio, and CO₂ efflux. Riparian CO₂e was more bulk density-dependent, while upland CO₂e showed greater dependence on TOC. The C:N ratio showed a higher mean value in the reference soils (CAL_ref and RZ_ref) than in the other soils (P < 0.05). The total nitrogen (TN), total protein (TP), and NH₄-N (ammonium‑nitrogen) showed the following trend: RSRZ > CAL > RRZ > RZ_ref > CAL_ref. The stepwise multiple regression models illustrated that soil moisture was the primary regulator of the C:N ratio and CO₂ efflux in the upland soils while the temperature in the riparian soils. These intrinsic soil variables resulted in 1.15 to 2.26 times higher CO₂ efflux from the cultivated soils (CAL, RSRZ, and RRZ) than from the reference soils. Hence, the present study revealed how agricultural practices tangibly increase the riparian system's carbon footprint while offering unsustainable livelihood options to farmers.