Influence of tree cover on herbaceous above- and below-ground phytomass in the Sahelian zone of Senegal

An experimental study was undertaken on a complex ecological system in the semi-arid Sahelian region of Senegal. The effects of tree cover on the above- and below-ground phytomass of the herbaceous layer were studied. The results show that: (1) herbaceous above-ground production was 1•5 to 4 times greater under the canopy than in the open sun light; (2) understory root phytomass was about two-fold greater than the root phytomass of the open grassland; and (3) the root/shoot ratio was 2•5 higher in the open than in the shade. Increased herbaceous layer productivity was interpreted as a result of better climatic conditions and greater soil fertility within the canopy zones. By promoting the development of herbaceous vegetation, trees increase the long-term production potential of the zone and, in consequence, improve conditions for livestock husbandry.