Measuring forest floor and canopy interception in a savannah ecosystem

Abstract

Interception is one of the most underestimated processes of the hydrological cycle. However, it amounts to a substantial part of the terrestrial evaporation and forms a direct feedback of moisture to the atmosphere which is important to sustain continental rainfall. Most investigations on interception focus on canopy interception only, whereas the interception by the surface and forest floor may be of same order of magnitude. Moreover there is a regional bias. Most research has been carried out in Europe and America and little is known about interception in Africa. This paper presents a study on forest floor and canopy interception in a savannah ecosystem. The study deals with both interception storage capacity of different vegetation types and the related moisture fluxes. The interception storage capacity of Msasa leaf litter and of Thatching grass is 1.8mm and 1.5mm respectively. This water storage capacity is dependent on storm intensity, with high intensity storms resulting in smaller storage capacity than less intensive storms. Canopy interception for the study period averaged 25% of the total rainfall, which is comparable with other studies. More importantly, the study revealed that combining canopy and forest floor interception yields a total interception flux amounting to 37% of the rainfall, or close to 50% of the total evaporation. This is a significant amount which implies that interception of both canopy and forest floor should be included in hydrological modelling and that interception is relevant for water management.