Continuous observations of CO2, H2O and CH4 exchange in an East-African rangeland

Semi-arid rangelands, common across Sub-Saharan Africa (SSA), are under increased anthropogenic pressure by a growing population and the necessity to produce sufficient amounts of food and nutrition. Rangelands in SSA are characterized by nutrient-poor soils and distinct wet and dry season(s). Due to the soil and climate combination, conventional crop farming is often not feasible without additional inputs in terms of water and mineral fertilizer. Instead, livestock keeping constitutes a valuable option to use these marginal lands and has been practiced in SSA for centuries. As a result, livestock and wildlife jointly feed on these pastures, a trait that distinguishes these systems from most western rangelands, where large herbivore herds are the exception rather than the norm. To date a thorough, climate-smart assessment that includes continuous greenhouse gas (GHG) exchange measurements in combined wildlife-livestock systems has not been undertaken. Here we provide eddy covariance (EC) measurements of CO₂/CH₄/H₂O from Kapiti Research Station in Kenya - a benchmark site for sustainable food production while also hosting wildlife. The GHG exchange measurements were complemented with wildlife camera traps to monitor both animal movement as well as plant phenology in the footprint of the EC tower. Our results show continuous CO₂ uptake during the wet seasons with considerable CO₂ emissions following distinct (>10mm) precipitation events after prolonged dry periods. Temporal dynamics of net ecosystem exchange of CO₂ was strongly correlated with canopy greenness (green chromatic coordinate) derived from field camera imagery. Methane flux measurements were highly variable and were particularly related to the presence of wildlife and/or livestock in the fetch of the EC tower. Our data suggest that these rangeland systems are accumulating carbon and thus compensate the methane emissions from livestock.