Spatial distribution of soil carbon inputs in permanent grassland vs. cropland in hedge agroforestry systems

Abstract 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 in two crop-livestock systems in Normandy, France. The two sites selected consisted of a permanent grassland or a cropland succession (i.e. annual crops and temporary grassland), each with similar adjacent hedges. At both sites, C inputs from fine roots, hedge leaf litter, organic fertilisation, crop/grass residues and grazing were measured from 0–30 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 0–90 cm in depth at the same distances. Results showed that in the cropland there was higher C inputs from fine-root turnover and hedge leaf litter at 1 and 3 m from the hedge and from crop residues at 10 m from the hedge. In comparison, the grassland received more C inputs 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.