Laboratoire de Microbiologie des Sols, Institut Français de Recherche Scientifique pour le Developpement en Cooperation, BP 1386, Dakar, Senegal.
Appl Environ Microbiol. 1992 Aug;58(8):2415-9. doi: 10.1128/aem.58.8.2415-2419.1992.
Soil cores were drilled under the leguminous tree Acacia albida growing in two different ecoclimatic zones of West Africa: the Sahelian area (100 to 500 mm of annual rainfall) and the Sudano-Guinean area (1,000 to 1,500 mm of annual rainfall). Soil samples were collected at different depths from the surface down to the water table level and analyzed for the presence of rhizobia able to nodulate A. albida. In both areas, population densities of rhizobia were substantially greater near the water table than near the surface. In the Sahelian area, rhizobia were present as deep as 34 m at a concentration of 1.3 x 10/g of soil. In the Sudano-Guinean area, population densities at 0.5 to 4.5 m depth were higher than in the Sahelian area and, at several depths, comparable to that of temperate soils supporting legume crops (10 rhizobia per g of soil). Surface and deep soil isolates from all four sites were found to be slow-growing rhizobia (Bradyrhizobium sp.). The proportion of effective isolates was almost the same within surface and deep soils.
在西非两个不同的生态气候区（萨赫勒地区和苏丹-几内亚地区），在豆科树木金合欢（Acacia albida）下钻取土壤芯。从地表到地下水位的不同深度采集土壤样本，并分析能够结瘤 A. albida 的根瘤菌。在这两个地区，靠近地下水位的根瘤菌的种群密度远远大于靠近地表的根瘤菌的种群密度。在萨赫勒地区，根瘤菌的存在深度可达 34 米，土壤浓度为 1.3 x 10/g。在苏丹-几内亚地区，0.5 至 4.5 米深度的种群密度高于萨赫勒地区，在几个深度处，与支持豆科作物的温带土壤的种群密度相当（每克土壤 10 个根瘤菌）。从所有四个地点的表层和深层土壤中分离出的细菌都是生长缓慢的根瘤菌（慢生根瘤菌属）。有效分离株在表层和深层土壤中的比例几乎相同。
