Ecosystem dynamics and services of Sahelian rangeland

Sahel Belt is the region south of the Sahara Desert that is characterized by a short rainy season (around 150 mm and 600 mm of rainfall per year) with an important inter-annual variability. The Sahelian vegetation is dry savanna that is composed of a layer of annual herbaceous plants and scattered perennial individuals (perennial herbs, bushes and trees). This vegetation is mainly used for livestock pastoralism.
In Senegal, within the “pastoralism and drylands” platform in partnership, research activities are conducted to understand the dynamics of these ecosystems and the services that they provided.
—Dynamics of the plant community during the rainy season especially regarding the distribution of rainfall during the rainy season and the impact of livestock (defoliation, trampling, nutriments recycling). We assessed these dynamics with field monitoring and control condition (rainfall, grazing) experimentations. Indirect measurements using optical tools will be useful to monitor this dynamic. We test and would test NIRS, hyperspectral camera, 3D mapping and plenoptic cameras to evaluate the different descriptors of plant biodiversity.
—Long term dynamics of vegetation diversity with climate variability The Sahel undergo several dryness periods during the last century that strongly affected the vegetation followed by wetter periods. We will use different approaches to analyse the trends of vegetation over several decades: First, we will use remote sensing to evaluate the change in some ecosystem proprieties (biomass, tree cover). Secondly, we assessed the species turnover using historical databases (FLOTROP database). Finally, we want to assess the change in plant functioning within a species using herbarium collection. We are currently testing NIRS on the herbarium specimen to assess functional traits.
—The ecosystem services evaluation of Sahelian rangelands. Some measurement of ecosystem services will be made across a large pedoclimatic gradient in the Senegalese pastoral zone. Secondly, we will develop an expert based assessment using a multicriteria analysis tools developed for this occasion (TATALE). The objective is to develop tools that assessed multiple ecosystem services using only botanical surveys or only remote sensing inputs.
During this seminar, first results and perspective on these topics will be presented.