1. Redistribution: lateral roots
Lateral roots commonly exceeding 10m in length, even with some shrubs
not higher than 2 m, are reported e.g. from Somalia [22]. Data from West
Africa indicate that lateral roots commonly reach up to 10 m in length, often
5 to 10 times as far as the crown radius [6, 29]. The maximum recorded were
those of Bombax costatum reaching 34m [55]. Most fine roots will be
concentrated in the topsoil, in view of the distribution of nutrients and water
in the soil. As a consequence, the lateral transport will be much more
important than the transport from deep soil layers. The lateral transport of
nutrients leads to a nutrient concentration under the woody plant at the
expense of a nutrient depletion at some distance. An evenly scattered woody
plant population would be able to exploit all topsoil if total crown cover is
10% and the horizontal root extension of the individual woody plants is
three times the crown diameter.