Hedges Increase Carbon Storage Differently Between the Particulate Organic Matter and Mineral Associated Organic Matter Fractions Along the Soil Profile

ABSTRACT Hedge agroforestry systems have a high potential to store additional carbon in field margins and are considered able to help mitigate climate change. However, the influence of hedges on the distribution of soil organic carbon among particulate organic matter and mineral‐associated organic matter fractions along the soil profile is not fully understood, especially for deep soil layers. Thus, the objective of this study was to explore the influence of hedges on the distribution of soil organic carbon stocks between soil fractions and analyze the variability in this distribution among depths for different land uses in an agricultural landscape. To this end, 18 study sites, corresponding to fields next to hedges more than 70 years old, were sampled to determine the distribution of soil organic carbon stocks between soil fractions at different depths (0–90 cm) near the hedges and their adjacent fields. The results showed that the presence of hedges significantly increased soil organic carbon stocks in the particulate organic matter fraction in the entire soil profile and primarily from 0 to 30 cm in depth. The study sites with a grass strip at 1 m from the hedge, with high clay content and higher C inputs near the hedge than in the adjacent field, had the largest additional soil organic carbon stocks due to the presence of the hedge. These results show that most additional stocks due to the presence of hedges are easily accessible and highly sensitive to change in the management of hedges and their adjacent fields.