Regional assessment of gully systems in a hilly olive-orchard dominated landscape

Abstract

Olive orchards dominate the land use at the hills of Afrin area, and olive oil represents the most important cash income source for rural communities in this area. However, olive yields in many orchards have been decreasing steadily over the last 20 years (Hoorelbeke, 2006). The major reason for the yield decline is the severe land degradation taking place in this region. Deforestation, expansion of olive production into steeper areas, and inappropriate land management practices, accelerated the rate of soil erosion. Especially the replacement of mule contour tillage by the cheaper up-and-down tractor tillage during the 1970’s was very detrimental. Tractor tillage not only moves down sizable amounts of soil during every tillage run, but also the consequent (mostly) vertical furrows stimulate water-induced soil erosion. The widespread presence of rills and gullies during the rainy season is a clear indicator of the severity of this problem. It is not exceptional to see that the parent material is surfacing, which indicates that a complete loss of the surface soil layer. However, gully systems are mere symptoms of ongoing degradation rather than the cause of degradation itself (Stocking et al., 2001). In order to facilitate the development of an effective soil conservation strategy for olive-dominated hill landscapes, the main focus of this study was to assess the severity of gully systems and to increase the understanding of the causes of gully system development.