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Title: Ecology of endomycorrhizas in some Cameroon forests with respect to species of Terminalia
Author: Musoko, Mbangu Olive
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1991
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The success of reafforestation schemes depends largely on the silvicultural systems employed. An indication of the ecological sensitivity of such practices can be gauged from the extent to which the soils physical, chemical and microbiological properties are altered. Of particular interest is the impact on the vescicular-arbuscular mycorrhizal (VAM) fungi as they play an important role in ensuring that forest trees especially those growing on nutrient deficient soils acquire sufficient mineral nutrients for growth. This study therefore set out to examine the effects of different methods of site preparation (Manual 'recru', mechanical 'recru' and complete clearance) and the subsequent outplanting with Terminalia ivorensis on the VAM population dynamics in the Mbalmayo Forest in Cameroon. Observations made prior to site preparation indicated the presence of an array of 17 VAM fungi belonging to the generas Acaulospora, Glomus, Sclerocystis and Scutellispora. Of the 17 fungi, one, Glomus etunicatum always represented more than 50% of the spore population. The importance of the tree component of the forest vegetation as reservoirs of VAM inocula was evident from, a) the higher number of spores in association with T. superba compared with shrubs and b) the peak in spore density close to T. superba trees (2.5m). Seasonal effects were suspected as many VAM fungi sporulated more profusely in the dry season (February, 1987) compared to the two rainy seasons (August 1987 and August 1988). Site preparation led to a dramatic reduction in spore number with the completely cleared plot losing 65% of its initial spore population. One year after planting, however, mean spore numbers had increased dramatically in all cleared plots, a major cause of the increase being the increase in root densities from the planted T. ivorensis and the invasive ruderal Eupatorium odoratum and pioneer tree Musangacecropioides. In the mechanically and completely cleared plots the sharp rise in spore numbers was mainly by the fungal aggregate G. occultum/A. scrobiculata which sporulated profusely in the presence of the invasive ruderal Eupatorium odoratum. The amounts of infection within the roots of T. ivorensis 1.5 years after planting in the manual and mechanical 'recru' plots were significantly greater than observed within T. ivorensis roots in the completely cleared plot. These differences may be related to the initial drop in spore numbers following site preparation, the disruption of the VAM hyphal networks in soil and/or the increasing dominance of G. occultum/A. scrobiculata, a type believed to be more associated with Eupatorium odoratum and hence possibly less effective on T. ivorensis. The value of the silvicultural procedures that were less destructive appeared to be reflected in tree survival.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available