Effect of Farming on the Vegetation Structure, Soil Properties and Termite Assemblages in the Northern Congo Basin

The growing human population requires vast amounts of supplies that are satisfied by a large agricultural expansion leading to alarming deforestation of tropical forests. Agriculture in the large part now is unsustainable as tropical soils are relatively nutrient poor, the amount of organic matter decreases fast and the soil invertebrates and microorganisms vanish over time. From a socio-economic point of view, agroforestry is a sustainable alternative to slash-and-burn practices, but its impact on termites, major macroinvertebrates responsible for the organic matter turnover, is poorly understood. Furthermore, other vegetation layers besides tree canopy are rarely included in studies despite their strong effect on soil macrofauna. Thus, we investigated the impact of human activities in Southern Cameroon by analysing the biomass of termites, the soil properties, the vegetation structure at three different classes (trees, shrubs and herbs) and the amount of raw vegetal material along a land-use gradient of primary forest - secondary forest - cocoa agroforestry - maize cropland. Within each of the habitats, two independent areas of 1 ha each were laid out for samples collection. Our results show similar trends for all variables, with a reduction of organic carbon as well as available micronutrients, plant diversity and abundance and dead plant matter stocks along the land-use intensification. The same trend is shown by the abundance and biomass of termites, best exemplified by the absence of soil-feeding termites in the maize cropland. We thus recommend for support to nature-friendly agroforestry systems preserving a large share of the original soil invertebrates.