Soil and organic carbon redistribution in a recently burned Mediterranean hillslope affected by water erosion processes

• Published in: Geoderma 2022-01, Vol.406, p.115539, Article 115539
• Main Authors: Campo, Julian, Cammeraat, Erik L.H., Gimeno-García, Eugenia, Andreu, Vicente
• Format: Article
• Language: English
• Subjects: Connectivity; Coupled hillslopes; Density fractionation; Forest fires; Soil organic carbon sink
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2021.115539

[Display omitted] •SOC content was homogenized at hillslope positions in burned Mediterranean soils.•Burned soils have different distributions of aggregate mass (size and density) and SOC (density).•Four rains mobilised high sediment and SOC amounts (role of soil erosion as C sink).•OC was initially transported as non-protected (FLF > OLF > HF) and later as protected (HF > FLF > OLF). Forest fires cause many changes in the physical, chemical and biological soil properties such as aggregation and soil organic carbon contents (SOC) as well as on soil hydrology and erosion processes. Most studies on post-fire soil erosion in Mediterranean environments have been plot-based and research at hillslope or broader scale is scarce. Understanding SOC nature, distribution and modifications, as produced by forest fires and erosion, has become crucial to model and define the role of soil erosion as source or sink of C, and to sustainably manage ecosystem services related to the soil resource. This research provides data about the loss and redistribution of soil and SOC in a Mediterranean forest hillslope burned with high severity, at the Natural Park of Sierra de Espadán, Spain. Soil was sampled in coupled hillslopes (ca. 0.25 ha) (BU: burned, CO: control) at bottom (depositional), middle (transport) and top positions (eroding) at two depths (0–2 cm, 2–5 cm), and under two environments (UC: under canopy soil, BS: bare soil). Sediments were collected after each erosive event along one year, and yields were calculated. Samples were analysed to assess aggregate stability (AS), size and density fractionations, SOC contents and stocks. The main hypothesis is that fire affects soil characteristics related to aggregation and SOC stabilization and, together with erosion processes, may modify SOC distribution within aggregates and the burned hillslope. Soils were in general very stable, but some differences in the results of the methods used were observed. Significant differences were found for the environment (under canopy vs bare) and soil depth but not for slope position. SOC content was high both at BU and CO with no significant differences. In the BU hillslope, a homogenization of SOC contents was observed along the hillslope, while in the CO, a higher SOC content was measured in the depositional and transport sites than in the eroding one. Similar trends were observed for SOC stocks. Only four erosive rain events were registered in this study, which generated no sediment y