Edge Influence in a Semi-Deciduous Tropical Forest: An Investigation of Soil Organic Carbon Fractions

Recent studies have proven the sensitivity of soil organic carbon (SOC) in responding to variations imposed by tropical forest fragmentation, which may reflect changes in both its quantity and quality. Despite this, studies evaluating soil carbon fractions as an edge effect indicator are still non-existent. We developed this work asking: How do the oxidizable fractions of soil organic carbon (OFSOC) respond to the edge effect in fragments of semi-deciduous seasonal forest? Is this response influenced by the size of the forest fragment? The study was conducted in Vitória da Conquista, Bahia, Brazil, in three forest fragments with different sizes. Thus, three sampling sections were defined in each fragment: edge (0–10 m), transition (40–50 m), and interior. Soil samples were collected at a depth of 0–10 cm. The SOC was divided into three fractions (LC—labile carbon, MLC—moderately labile carbon, and LLC—low labile carbon), adopting the chemical method based on oxidation degrees. Reductions in the SOC (28.2%), LC (17.4%), and MLC content (66.7%) were observed at the edge in the small fragment. There was a reduction of SOC (21.3%) and LLC (39.0%) at the edge in the medium fragment, while MLC showed an increase at the edge (70.4%). The OFSOC were able to respond to the changes imposed by the edge effect, with emphasis on the LC and MLC fractions in smaller fragments. The forest fragment size influenced the level of changes caused by the edge effect in OFSOC, showing greater susceptibility in smaller fragments.