The Relevance of Mycorrhizal Research to Conservation and Development Strategies in Semi-Arid Environments

Pease, Arnold Paul (2002). The Relevance of Mycorrhizal Research to Conservation and Development Strategies in Semi-Arid Environments. BPhil thesis The Open University.



Semi-arid regions have traditionally supported substantial human populations but have seen their integrity and productivity seriously compromised by over-exploitation when population growth has coincided with extended droughts. Symbiotic relationships between plants and soil microorganisms are particularly important in nutrient-poor, drought-stressed environments, but are undermined when drastic reduction in plant cover exposes fragile soils to erosion or crusting, leading to desertification. In such conditions, revegetation may fail unless plants and microsymbionts are restored together.

A century of mycorrhizal research has begun to shed light on some of the key organisms and processes operating in undisturbed soils, but knowledge is still extremely sketchy. Little is known of the factors determining the distribution of particular fungal species, though some cope with disturbance better than others, and consequently the fimgal species composition tends to change when land is cultivated. Undisturbed natural vegetation, particularly the rhizospheres of healthy trees, is likely to contain propagules of a mixture of effective AM species, together with a range of other soil microorganisms which may also have important symbiotic roles, and thus be a good local source of inoculum for tree nurseries. Munro et al (1999) advocate an inoculation strategy based on this insight. Their procedure could be implemented in village tree nurseries, and this is strongly recommended.

Savanna-type ecosystems are resilient in the face of drought. Agroforestry mimics these natural ecosystems, and is popular as a way of protecting and improving the productivity of semi-arid land. A range of suitable species is profiled, but the main criterion should be local interest and demand.

Researchers in Senegal identified two AMF species associated with Faidherbia albida at a depth of 34 m. Deep-rooting trees are key elements in dryland ecology, and experimental investigation of the possible role of Glomus fasciculatum and Gigaspora margarita as inoculum for tree seedlings is suggested.

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