Mycorrhizas in Zambian Trees in Relation to Host Taxonomy, Vegetation Type and Successional Patterns

Abstract

(1) Thirteen species of common Zambian trees were found to be ectomycorrhizal and ten endomycorrhizal. (2) Observations of ectomycorrhizas in Brachystegia, Julbernardia (both Caesalpiniaceae), Monotes (Dipterocarpaceae) and Uapaca (Euphorbiaceae) confirmed earlier reports, while ectomycorrhizas in Faurea (Proteaceae), Isoberlinia (Caesalpiniaceae), Marquesia (Dipterocarpaceae) and Pericopsis (Papilionaceae) are reported for the first time. (3) These genera constituted about 70% of the basal area in a representative miombo (Brachystegia-Isoberlinia-Julbernardia) woodland stand-a high proportion for a diverse tropical ecosystem. (4) Associated species in the miombo were endomycorrhizal as were principal species of the Zambian Kalahari sand vegetation, namely species of Baikiaea, Erythrophleum, Guibourtia (all Caesalpiniaceae) and Pterocarpus (Papilionaceae). Colophospermum mopane (Caesalpiniaceae), a species often forming pure stands, was also endomycorrhizal. (5) The ecological groups of species suggested by Lawton (1978) as typical of the successional stages from open fire-degraded chipya woodland to closed dry evergreen mateshi forest via miombo woodland, show differences in the occurrence of mycorrhizas. In the chipya group, endomycorrhizal tree species predominate and ectomycorrhizal species are sparse. Ectomycorrhizal Uapaca spp. invade chipya woodland, and later provide cover for the regeneration of ectomycorrhizal genera forming the miombo group-Brachystegia, Isoberlinia, Julbernardia and Monotes-and for ectomycorrhizal Marquesia of the mateshi group. In the mateshi forest group, there is a mixture of ectoand endomycorrhizal tree species.