Spatial distribution of soil carbon inputs in two contrasted hedge agroforestry systems

Hedge agroforestry systems are known for their potential to store large amounts of carbon (C) in agricultural soils, but there remains a lack of understanding about the spatial distribution of soil organic C (SOC) stocks near hedges. This study thus focused on the spatial organisation of C inputs near hedges associations with two cropping systems typical of mixed farming in Normandy, France. The two sites selected consisted of mixed hedges adjacent to a permanent grassland or a cropland rotation (i.e. annual crops and temporary grassland). At both sites, C inputs from fine roots, hedge leaf litter, applied organic fertilisation, crop/grass residues and grazing cattle were measured from 0 to 30 cm in depth at distances of 1, 3 and 10 m from the hedge. At the same time, SOC stocks and their distribution in the fine and coarse fractions of the soil were measured from 0 to 90 cm in depth at the same distances. showed higher C inputs from fine-root turnover and hedge leaf litter at 1 and 3 m in cropland compared to 10 m, while C inputs from crop residues were higher at 10 m. In grassland, more C inputs came from fine-root turnover and grass residues at 1 and 3 m from the hedge. C input from hedge leaf litter was associated with high SOC storage in the coarse soil fraction, while C inputs from fine roots were associated with high SOC storage in the fine soil fraction. While the results showed that hedges contributed less than expected to soil C inputs, they also showed the need to maintain the current hedge linear layout to avoid a rapid decline in soil carbon stocks derived from hedges, which are largely made up of labile carbon. • Distribution of carbon inputs near mixed hedges bordering fields was investigated. • Carbon input increased near the hedge from fine-root turnover and hedge leaf litter. • Hedge leaf litter carbon input was mainly stored in the soil coarse fraction. • Fine root carbon input was mainly stored in the soil fine fraction.