Ecosystem services of termites (Blattoidea: Termitoidae) in the traditional soil restoration and cropping system Zaï in northern Burkina Faso (West Africa)

The present study provides evidence of the effectiveness of some termite species in restoring barren soil and in maintaining long-term soil productivity, thereby facilitating sustainable agriculture in sub-Saharan West Africa. Fungus-growers, in particular, move large quantities of soil to cover their food sources with 'soil sheetings', which protect the termites during foraging. We selected study sites in northern Burkina Faso from four age-stages of the traditional restoration system Zaï, thus spanning three decades of soil restoration-barren, crusted land, a millet field, and two reforested sites. In a randomized block design, termites were attracted to different organic materials. The aim was to assess the impact of their foraging structures (soil sheetings, foraging holes) on the restoration progress. We quantified soil turnover by termites, macroporosity, water infiltration rate, and physicochemical soil properties. Fungus-growing Odontotermes and Macrotermes species were the decisive soil engineers throughout the year, but only Odontotermes initiated the restoration process. The dry weight of soil bioturbated during the dry season ranged between 216 and 32 tons ha−1 mon−1 in the most rehabilitated Zaï forest and the barren area, respectively. By creating tunnels, the foraging activity of termites increased the water infiltration rate by a factor of 2 to 4. Sheetings built on compost and hay showed significant increase in most parameters relevant for plant growth, especially during the dry season. However, the benefits resulting from the termites' tunnelling activities (improved water availability and soil aeration via macropores, soil turnover) are in the early stages of Zaï restoration likely to be more essential than the increased nutrient contents in sheeting soil, since water deficit leads to sapling mortality much faster than nutrient shortage. Our study revealed that the impact of termites is dependent on the particular species and their ecological requirements. Further studies in other areas are urgently required to clarify how generally valid our results are.