Ecological indicators of the best period to replant fallow zones in Niger. (Surveillance environnementale a long terme dans les zones arides et semi-arides (Long-term environmental monitoring in arid and semiarid lands))

摘要

With a view to understanding Sahelian production systems, the Sahel and Sahara Observatory (SSO) has launched long term studies. A concrete case study conducted in Niger presents results about long term vegetation monitoring and provides information on the impact of environmental factors on vegetation dynamics in 6 fenced fallows. The indicators that can help the local population make decisions about sustainable land management have been identified and current soil surface conditions as well as plant communities have been characterized. Data measurement is based on a permanent mechanism comprising a quadrat point network, the collection of herbaceous phytomass and the assessment of different environmental parameters (topography, rainfall, soil surface conditions). Results show that the observatory's flora is dominated by annual species which are very sensitive to rainfall and topography. We have identified two relevant indicators to alert farmers to cultivate fallows again so as to optimize their productivity (development of algal crust and stimulation of termite activities associated with the increase of litter cover). Phytodiversity and biological land productivity can thus be increased.