Local communities in southern Africa derive many benefi ts from marula [Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro]. These include the contribution of this species towards health, nutrition, food security and conservation by sharing local skills and knowledge related to it. Marula fruits can be eaten fresh, squeezed to make juice, brewed in traditional beer or used to make jam and jelly. The kernels are also edible and can be pressed to extract oil for cooking and cosmetics, i.e., for skin and hair application. The bark, roots, seeds and leaves are exploited for traditional medicinal purposes. Marula has acquired signifi cant commercial value since its fruits and other products have entered local, regional and international trade in southern Africa. To diversify fruit production and satisfy the increasing demands for this resource, several domestication initiatives have been carried out at regional and international levels. The accumulated knowledge and skills relevant to the establishment and commercialization of marula therefore provide an effective guide in areas where marula remains undomesticated or underutilized. We discuss the great importance of marula in southern Africa to reveal its great potential to regions where it remains unexploited.

In arid to semi-arid grasslands and savannas, plant growth, population dynamics, and productivity are consistently and strongly limited by soil water and nutrient availability. Adaptive traits of the root systems of grasses in these ecosystems are crucial to their ability to cope with strong water and/or nutrient limitation and the increasing drought stress associated with ecosystem degradation or projected climate change. We studied 18 grass species in semi-arid savanna of the Kalahari region of Botswana to quantify interspecific variation in three important root system traits including root system architecture, rhizosheath thickness and mycorrhizal colonization. Droughttolerant species and shorter-lived species showed greater rhizosheath thickness and fine root development but lower mycorrhizal colonization compared to later successional climax grasses and those characteristic of wetter sites. In addition, there was a significant positive correlation between root fibrousness index and rhizosheath thickness among species and a weak negative correlation between root fibrousness index and mycorrhizal colonization.These patterns suggest that an extensive fine root system and rhizosheath development may be important complementary traits of grasses coping with drought conditions, the former aiding in the acquisition of water by the grass plant and the latter aiding in water uptake and retention, and reducing water loss in the rhizosphere. Within species, both rhizosheath development and mycorrhizal colonization were significantly greater in a wet year than in a year with below-average precipitation. The observed patterns suggest that the primary benefit of rhizosheath development in African savanna grasses is improved drought tolerance and that it is a plastic trait that can be adjusted annually to changing environmental conditions. The functioning of mycorrhizal symbiosis is likely to be relatively more important in infertile savannas where nutrient limitation is higher relative to water limitation.

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Faidherbia albida is an ideal agroforestry tree commonly intercropped with annual crops like millet and groundnuts in the dry and densely populated areas of Africa. With its peculiar reverse phenology, it makes growth demands at a different time from that of crops. In addition, it deposits great amount of organic fertilizer on food crops. Leaves entering soils are comparable to fertilization of almost 50 t·ha −1 ·year −1 of manure in dense stands of 50 large trees per ha. These nutrients help maximize agricultural production and reduce the need for a fallow period on poorer soils. Research has shown that millet grown under F. albida yielded 2.5 and 3.4 fold increases in grain and protein, respectively. Animals eat pods which contain mean amounts of crude protein of 20.63% and carbohydrate of 40.1% in seeds. Moreover, the continued existence of F. albida in agroforestry parklands as in Ethiopia and Mali signifi es the success of traditional conservation measures. Modern scientists have also developed much interest in the role of agroforestry in maintaining long-term biological balance between agriculture and livestock production systems. To ensure food security, which still remains a major challenge in sub-Saharan Africa, and concurrently minimize environmental degradation, promotion of agroforestry that specifi cally involves indigenous trees is crucial. We discuss the prospective role of F. albida in alleviating poverty while simultaneously protecting the environment from factors associated with, for example, deforestation and loss of biodiversity. The overall aim is to promote wide-scale adoption of F. albida as a valuable tree crop in farming systems, particularly in those areas where it remains unexploited.

Three semi-arid savanna grasses in Botswana (Stipagrostis uniplumis, Eragrostis lehmanniana, and Aristida stipitata) were sampled to quantify their belowground bud banks during the dormant season and to estimate their relative allocation to vegetative and sexual reproduction. Bud banks of these African perennial caespitose grasses were also compared with four perennial caespitose grasses of semi-arid North American grasslands. The three African grasses each maintained approximately two buds per tiller and showed a high percentage (88-99%) of tillers producing seed. Only E. lehmanniana produced new aerial tillers from axillary buds at elevated nodes on the stem as well as from the belowground bud bank. Compared with species of North American grasslands, these African grasses produced fewer belowground buds but showed a much higher percentage of tillers producing seed. These patterns indicate relatively greater belowground meristem limitation, lower allocation to vegetative reproduction (tillering) and higher allocation to seed reproduction in these African grasses, although studies of more species are needed to assess the generality of this pattern. The management of savannas in ways that favour the maintenance of a reserve population of belowground buds may increase the ability of grasses to respond to pulses of resource availability, increase their compensatory growth capacity following grazing or drought, and decrease the invasibility of these plant communities by exotic species, whereas maintaining allocation to sexual reproduction may be important for conserving genetic variation and enhancing their capacity to adapt to environmental change.