Contrasting rooting patterns of some arid-zone fruit tree species from Botswana - I. Fine root distribution

To assess the possible degree of root competition from fruit trees which could potentially be used in agroforestry systems,. ne root density of fruit trees Strychnos cocculoides BAK., Strychnos spinosa LAM. (Loganiaceae) and Vangueria infausta BURCH. (Rubiaceae), as well as from the shrubby species, Grewia flava DC. (Tiliaceae) was investigated. Vangueria infausta had the highest. ne root densities in both vertical and horizontal extensions. In Vangueria infausta. ne root density decreased with increasing soil depth. For the other species in the 80 cm soil pro. le investigated, no significant changes in. ne root density with soil depth were found. For Strychnos cocculoides almost no. ne roots were detected in the upper soil horizon (0-20 cm). Using fine root surface area densities, exploration and exploitation indices were calculated. Vangueria infausta had the highest value of the exploration index compared to the other species. For use in agroforestry systems Vangueria infausta was estimated to be the most competitive of the investigated species, whereas Strychnos cocculoides seems to be the less competitive. Strychnos cocculoides has additionally spatial arrangements of. ne roots favourable for agroforestry, slowly increasing with depth and additionally low concentrations in upper soil layers.