THE ROOTING PATTERNS OF WOODY AND HERBACEOUS PLANTS IN A SAVANNA - ARE THEY COMPLEMENTARY OR IN COMPETITION

Root patterns of three woody plants are described in relation to water profiles and average root depth of annual species on three contrasted soil types along a toposequence in a watershed of northern Cameroon. This watershed is in a Sudano-Sahelian savanna where mean annual preci pitation is 800 mm, entirely restricted to the period May-June to Sept ember-October. Results show great variations of root structure of wood y plants according to the distribution of water in the soil during one year. Consequently, under the same climatic conditions, soil depths e xploited by woody plants and herbaceous plants can either be the same or not. In the most degraded soils, water does not infiltrate deeply a nd roots of the two components of savanna are limited to the upper hor izons. On the other types of soil, root distribution depends on the so il profile.