Flux heterogeneity and evapotranspiration partitioning in a sparse canopy: the fallow savanna

This paper focuses on in situ measurements obtained during the intensive observation period of the HAPEX-Sahel experiment. Micrometeorological measurements and trunk sap flow monitoring were combined to analyse transfer characteristics of a fallow savanna site within the East Central Supersite. Results show that the shrub canopy heterogeneity induces a large spatial variability of solar irradiance, soil heat flux and sensible and latent heat fluxes at the grassland level. This variability is induced by both a “shade effect” and a “wake effect”. Both shrubs and grassland provide sources of vapour, but the partitioning of evapotranspiration between these two components varies considerably with soil surface water availability.