Mycorrhizal status of indigenous trees in dry Afromontane forests of Ethiopia

Abstract

The dry Afromontane forests in Ethiopia are composed of a number of indigenous tree species. Currently, indigenous trees are declining at an alarming rate in this ecosystem. The few reforestation programs, which have so far been undertaken, employ exotic tree species. This is mainly due to lack of knowledge on the environmental requirements of indigenous trees. Though there have been efforts to solve problems associated with the use of indigenous trees in the reforestation activities, information on the mycorrhizal symbiosis is still lacking. Investigation of roots of 11 indigenous trees, Albizia gummifera, Albizia schimperiana, Aningeria adolfi- friedericii, Croton machrostachyus, Ekebergia capensis, Hagenia abyssinica, Juniperus procera, Podocarpus falcatus, Prunus africana, Olea europaea ssp. cuspidata, and Syzygium guineense, revealed arbuscular mycorrhizal colonization. No evidence of ectomycorrhizal colonization was found. This is the first report on the mycorrhizal status of A. gummifera, A. schimperiana, A. adolfi- friedericii, E. capensis, H. abyssinica, P. africana and S. guineense. The mycorrhizas are characterized by dominantly intercellular hyphal growth, formation of arbuscules on intracellular hyphal branches and low frequency of hyphal coils which can be classified as an Arum-type of AM. The Arum-type of AM is reported for the first time in S. guineense (Myrtaceae), E. capensis (Meliaceae), A. adolfi- friedericii (Sapotaceae) and the gymnosperms J. procera and P. falcatus. Results established that arbuscular mycorrhizas (AM) are predominant in the dry Afromontane forests of Ethiopia. Therefore, AM should receive special attention in indigenous tree seedling production and restoration activities of the dry Afromontane ecosystems of the country.