Impacts of land use and topography on soil organic carbon in a Mediterranean landscape (north-western Tunisia)

摘要

Abstract. This study evaluates the impact of land use and topographicfeatures (slope and aspect) on soil organic carbon (SOC) within the WadiBeja watershed in north-western Tunisia. A soil spectral library was set upto assess the variation in the SOC for 1440 soil samples from four land usetypes (field crops, permanent crops, forest, and grazing land), three slopecategories (flat, moderate, and steep) and two aspects (north- andsouth-facing). For field crops, only one factor – slope – significantlyaffected SOC, with SOC content in north-facing areas appearing to be higherin flat areas (0.75 %) than in hilly areas (0.51 %). However, insouth-facing areas, SOC content was also higher in flat areas (0.74 %)than in hilly areas (0.50 %). For permanent crops, which wereinter-planted with field crops, the slope significantly affected SOCcontent, which improved to 0.97 % in flat north-facing and 0.96 % inflat south-facing areas, scoring higher than hilly south- and north-facingareas (0.79 %). In the grazing land use system, both of the investigatedfactors – aspect and slope – significantly affected the SOC content, whichwas significantly higher in flat areas (north-facing: 0.84 %,south-facing: 0.77 %) than in hilly areas (north-facing: 0.61 %,south-facing: 0.56 %). For the forest, none of the factors had asignificant effect on SOC content, which was higher in flat areas(north-facing: 1.15 %, south-facing: 1.14 %) than in steep areas(1.09 % in north-facing areas and 1.07 % in south-facing areas). Thisstudy highlights the ability of visible and near-infrared (VNIR)spectroscopy to quantify C in diverse soils collected over a large diversegeographic area in order to indicate that calibrations are feasible, andtherefore, assessing the variation of SOC content under land use andtopographic features (slope and aspect) will result in better sustainableland management planning.