Impact of topographic aspect and vegetation (native and reforested areas) on soil organic carbon and nitrogen budgets in Mediterranean natural areas

Soil organic carbon (SOC) plays a critical role in the global carbon (C) cycle, and C sequestration in forest soils can represent a C sink. A relevant question is how does SOC changes in space and time; consequently, the study of the influence of topographic aspect on SOC stocks (SOCS) is very important to build a complete understanding of the soil system. In this line, four topographic aspects, north (N), south (S), east (E) and west (W) were studied under two different plant communities; native forests (NF) and reforested areas (RF) in the Despenaperros Natural Park (S Spain). Five soil profiles were sampled at each of six different sites, 2 sites for NF (N and E) and 4 sites for RF (N, S, E and W). Soil properties were studied at different depths using soil control sections (S1: 0-25 cm; S2: 25-50 cm; S3: 50-75 cm). The results indicate that RF (N: 147.1 Mg ha(-1); E: 137.3 Mg ha(-1); W: 124.9 Mg ha(-1) and S: 87.0 Mg ha(-1)) had increased total SOCS compared to NF (N: 110.4 Mg ha(-1) and E: 80.9 Mg ha(-1)), and that SOCS in the N position were higher than in the other topographic aspects. Therefore, the results suggest that topographic aspect should be included in SOCS models and estimations at local and regional scales. (C) 2015 Elsevier B.V. All rights reserved.