Summary

The mid-Zambezi valley is an area of harsh climate, low population density, and below average agricultural productivity. These factors define it as a marginal agricultural region. The valley area has fertile, largely alluvial soils, flat topography, and high temperatures that support production of small grain cereals and cotton. Small grain cereals are normally supported by low input levels, while cotton requires high input levels. To reduce input costs, particularly in cotton production, fallowing is practiced. The low human population density affords opportunities for limited inputs and shifting cultivation, thus allowing development and practice of agricultural fallowing (extensification). Fallow units are at different stages of recovery, thus creating landscape mosaics that are at different levels of succession.

• How do ectomycorrhiza fungi vary in composition and diversity across fallows of different age (agricultural extensification gradient) in time and space?

 Ectomycorrhiza fungi express minute differences in community composition, differences that would otherwise be difficult to detect when assessed at the primary trophic level of vascular plants. They, therefore, indicate changes at much finer and earlier stages of community succession. This part of the study seeks to understand the nature of species richness across fallows of different age along an agricultural extensification gradient. It also seeks to understand the nature of infra-population genetic diversity across fallows of different ages. Thus, the study investigates inter-fallow diversity at species level, and at the same time, seeks to understand infra-specific (i.e. inter-population) diversity among fallows.

•   Are ectomycorrhiza fungi associated with the same host species in fallows of different age (i.e. if vascular species composition changes with fallow age, is this reflected in fungal species composition)? Put another way; Are there fungal host shifts across fallows of different ages? 

Past and ongoing studies have shown that vascular plant species composition changes with age of fallowing. Some species disappear, new ones emerge, yet others persist and become dominant up to climax community stage. Similarly, fungal species composition is expected to change with age of fallowing in response to host composition. This part of the study seeks to investigate plant/fungi interactions in fallows of different ages across a disturbance gradient.

Ectomycorrhiza fungi facilitate nutrient mobilisation and fixation by plants in an ecosystem. Studies have shown that fallowing facilitates regeneration of woody plant species. It is expected that increased woody species will be associated with increased ectomycorrhiza fungi diversity. This increased fungi diversity is, therefore, associated with ecosystem functional diversity in terms of nutrient mobilization and fixation, hence soil enrichment.

Primary Objective

The study seeks to understand the nature of ectomycorrhiza fungi community succession, diversity and pattern of host shifts across an agricultural disturbance gradient in the mid-Zambezi area.

 Specific objectives

• to record ectomycorrhiza fungi of the area and establish the fungal flora that is associated with fallowing;
• to compare species richness among fallows of different ages and natural woodlands as a way of determining community changes associated with succession;
• to assess infra-specific genetic diversity in dominant ectomycorrhiza fungi of the area; and
• to establish whether ectomycorrhiza fungi shift hosts in relation to community succession.