DISTRIBUTION OF ROOTS, ARBUSCULAR MYCORRHIZAL COLONIZATION AND SPORESAROUND FAST-GROWING TREE SPECIES IN SENEGAL

Roots and soil were sampled from around four leguminous tree species i n 10-year-old plots at Bandia, Senegal, Assessments of root concentrat ion (cm per 100 cm(3) soil) and mycorrhizal colonisation (% of root le ngth) were made and related to the abundance of spores in the soil and the above ground growth (stem diameter at 30 cm height) of the trees, Root concentrations in Acacia nilotica and Acacia tortilis plots were greater than those found in Prosopis juliflora and Acacia aneura plot s at all three depths examined (0-10, 10-25, 25-50 cm), Root concentra tion decreased with soil depth in all plots and was greatest nearest t he tree in the Acacia nilotica and Acacia tortilis plots, Mycorrhizal colonisation was highest on Prosopis juliflora roots and lowest on Aca cia tortilis roots, Colonisation was not affected by distance from the tree and decreased with depth only in the Acacia aneura plot. Numbers of spores recovered from soils were generally low (27 per 100 g dry w t, soil) and were concentrated in the upper 10 cm of soil. Spores were most numerous in the Acacia aneura plot and least numerous in the Pro sopis juliflora plot, Positive relationships were found between spore numbers and root concentration in the Prosopis juliflora plot and betw een spore numbers and mycorrhizal colonisation in the Acacia aneura pl ot. Of the four tree species examined, root and mycorrhizal distributi ons of Prosopis juliflora and Acacia nilotica showed most promise for use in agroforestry systems.