Grewia Bicolor Research Articles

Utilization of edible wild plants and their contribution to household income in Gweta Village, central Botswana

Gweta Village is endowed with a variety of edible wild plants (EWPs) ranging from fruits and leafy vegetables to tubers utilised by the residents. The study focused on documenting and synthesising indigenous knowledge related to the use of EWPs and assess their contribution to household food supply and income in Gweta Village, central Botswana. Data were collected through household survey of forty five households and five key informants. Twenty four species were found that belong to thirteen families, used as source of food and beverage. Most utilised EWPs include Grewia flava, Grewia bicolor, Scloreocarya birrea, Amaranthus thunbergii, Cleome gynandra, Corchorus olitorius. They are the main source of food and income, and are harvested by almost everyone in the Village. About 52% of the respondents were engaged in the sale of nine EWPs, and the sale contributed between BWP 50.00 to more than BWP 400.00 per week. The study showed that women are predominant users and collectors of EWPs and children are regular harvesters in small quantities for consumption as snack. Furthermore, the study revealed that elephants are the major threat to diminishing of EWPs in the Village. Some of the Villagers have already started domestication of some treasured EWPs while others are eager to do so. The prior assumption that EWPs are of significant importance to the rural economy has been confirmed, and the results revealed that EWPs also assist in dietary diversity, food security and income generation. Further research work on EWPs on nutritional value and related health outcomes is needed. Also, there is a need for creating awareness of the public and policy realignment to promote and market EWPs.

Bio-Mechanical Investigation on the Physical Resilience of Selected Dominating Shrubs in Semi-Arid Region of Dodoma

Physical and mechanical disturbances which interfere with shrubs survival are very common in semi-arid regions. Biomechanical adoptive features of these shrubs therefore account for their competitive and survival possibilities. Current study investigated physico-ecological properties of five stem cuttings of selected dominating shrubs from Dodoma Municipal that explain their physical resilience. Experimental findings revealed that Acacia nilotica (AN) had the best mechanical adaptations by having the highest values of Young’s modulus of elasticity (E) 332.61 kPa, percentage critical height (PCH) 6.00, whole stem flexibility (WSF) 0.1, flexural stiffness (FS) 7.46 Nm2 as well as angle of deflection (AD). Ziziphus mucronata (ZM) was next to AN, followed by Grewia bicolor (GB) then Acacia tortilis (AT). Boscia grandiflora (BG) had the least mechanical adaptations with the lowest E of 20.94 kPa, PCH of 4.00, WSF of 0.09 as well as FS of 2.90 Nm2. This implied Acacia nilotica having the best ecological adaptations in the semi-arid region while Boscia grandiflora had the least adaptive feature compared to the rest.

Seasonal Selection Preferences for Woody Plants by Breeding Herds of African Elephants (Loxodonta africana) in a Woodland Savanna

To evaluate dynamics of elephant herbivory, we assessed seasonal preferences for woody plants by African elephant breeding herds in the southeastern part of Kruger National Park (KNP) between 2002 and 2005. Breeding herds had access to a variety of woody plants, and, of the 98 woody plant species that were recorded in the elephant's feeding areas, 63 species were utilized by observed animals. Data were recorded at 948 circular feeding sites (radius 5 m) during wet and dry seasons. Seasonal preference was measured by comparing selection of woody species in proportion to their estimated availability and then ranked according to the Manly alpha (α) index of preference. Animals demonstrated a selection preference in feeding on woody vegetation, andGrewia hexamita, Grewia bicolor, Grewia flavescens, andGrewia monticolawere selected consistently more over all seasons. In addition, our results indicate that elephant herds have a low preference for at least some of the woody species prone to extirpation and that feeding preferences for woody plants do not account for the association of elephants and riparian fringe habitat.

Medicinal plants used by the Bapedi traditional healers to treat diarrhoea in the Limpopo Province, South Africa

Ethnopharmacological relevanceThis paper provides ethnobotanical information on medicinal plants used to treat diarrhoea in the Limpopo Province, South Africa. Documentation of this nature usually provides the basis for selecting medicinal plants for future phytochemical and pharmaceutical studies aimed at developing new, effective and affordable plant-derived diarrhoea remedies. Aim of the studyTo record and document medicinal plants used by the Bapedi traditional healers to treat diarrhoea in the Limpopo Province, South Africa. Materials and methodsIn order to record and document medicinal plants used by the Bapedi traditional healers to treat diarrhoea, 51 healers from 17 municipalities covering Capricorn, Sekhukhune and Waterberg districts in the Limpopo Province, South Africa were interviewed between January and July 2011. Data collected included the names of plants, plant part(s) used, methods of herbal preparation, administration, dosage and duration of treatments. Voucher specimens of the plants used by the Bapedi traditional healers to treat diarrhoea were collected, identified and deposited as future reference material at the Larry-Leach Herbarium (UNIN), University of Limpopo. ResultsA total of 20 plant species representing 16 families and 20 genera were found to be commonly used by the Bapedi traditional healers to treat and manage diarrhoea in the Limpopo Province, South Africa. The largest proportion of the medicinal plants belonged to the families Anacardiaceae, Asteraceae, Fabaceae and Malvaceae (10% each). The most frequently used species were Punica granatum (39.2%), Grewia bicolor (33.3%), Dombeya rotundifolia (21.6%), Commiphora marlothii (19.6%) and Acacia senegal (13.7%). The roots were the most commonly used plant part (50%), followed by leaves (20%), bark (15%), fruits (10%), pericarp, seed, tuber and whole plants (5% each). Mono therapies based on preparations made from a single plant species were the most dominant (90%). All medicinal preparations were taken orally for 1 week or until diarrhoea subsided. The therapeutic claims of the medicinal plants documented in this study are well supported by literature, with 70% of the species having anti-diarrhoeal properties or are used as diarrhoea remedies both in South Africa and also in other countries. ConclusionThis study reveals that local communities in the Limpopo Province, South Africa still depend on traditional medicines for basic healthcare; and the use of traditional medicines is still an integral part of their socio-cultural life.

In vitro assessment of ruminal fermentation characteristics of tropical browse mixtures supplemented with yeast

AbstractAn in vitro ruminal gas production study was conducted to assess the effect of yeast supplementation on rumen fermentation of tanniniferous tropical browse mixtures prepared by mixing Berchemia discolor with Acacia brevispica, Acacia elatior, Acacia mellifera, Balanites aegyptiaca, Grewia bicolor or Zizyphus mucronata in a 1:1 dry weight ratio. The six browse mixtures were incubated with buffered rumen fluid alone or supplemented with dried Japanese Sake yeast (JSY) or polyethylene glycol (PEG). Ruminal gas production characteristics were evaluated using the Gompertz equation. The JSY addition increased gas production volume (P < 0.05) and numerically increased the maximum gas production rate constant. Time to reach the maximum gas production rate was shortened by PEG addition as compared to the JSY and control treatments. It is possible that JSY promoted the rumen microbial activity in addition to forming complexes with tannins thereby upgrading the in vitro ruminal digestion of tropical browse mixtures.

Diet preferences of a Western giant's (Lord Derby's) eland group in a Sahelian dry habitat

Abstract The diet of the critically endangered Western giant eland (Tragelaphus derbianus derbianus Gray, 1847) has never been studied. We studied the food preferences of a Western giant eland group translocated from its native Sudanian habitat to a wildlife reserve in a Sahelian area in relation to the abundance of food in the new habitat. The study generated the first qualitative and quantitative data on this eland subspecies' diet. The translocated group fed only on 33 different plant species available in its new habitat. Isoberlinia doka, and Julbernadia sp., two species eaten by the other eland subspecies did not occur here. The food preference for most ligneous species did correspond to their high availability in the translocation area (like Acacia seyal, 32.56% versus 28.26% abundance in the new habitat, Acacia ataxacantha, 19.7% versus 17.03%, and Azadirachta indica, 7.11% versus 4.71%; only Grewia bicolor, 7.48% versus 10.14% did not). In contrast, the food preference for many herbaceous species did not, as some were preferred (like Merremia pentaphylla, 35.41% versus 11.01%, and Peristrophe bicalyculata, 2.58% versus 0.00%), and others avoided (like Corchorus tridens, 1.72% versus 2.20%, Cucumis melo, 0.43% versus 5.73%, and Abutilon ramosum, 0.21% versus 7.05%). The most eaten Cassia tora (42.7%) was also the most abundant (36.56%). Our data will provide conservation managers with information on how to protect the species' natural environment and to make appropriate management decisions with respect to the proclamation of protected areas or the identification of core zones, mainly for future (re)introduction of satellite populations.

Diversity and abundance of insect visitors to flowers of trees and shrubs in a South African savannah

AbstractThis study presents the results of a landscape‐scale survey for insect floral visitors in the Skukuza Ranger District, Kruger National Park, South Africa. Floral visitors were sampled from flowering trees and shrubs along linear transects spanning the entire district. Six plant species were sampled in the late dry season (Acacia grandicornuta Gerstner, A. nigrescens Oliver, Cassia abbreviata Oliver, Combretum hereroense Schinz, Combretum zeyheri Sonder, Euclea divonorum Hiern), and eleven plant species were sampled during the rainy season (Acacia exuvialis Verdcourt, A. grandicornuta Gerstner, A. nilotica (L.) Willdenow, A. tortilis (Forsskal) Hayne, Dichrostachys cinerea Miquel, Flueggea virosa (Roxburgh) Baillon, Grewia bicolor Jussieu, G. flava De Candolle, G. flavescens Jussieu, G. monticola Sonder, and Peltophorum africanum Sonder). Coleoptera, Hymenoptera and Lepidoptera comprised the majority of floral visitors, while species of Blattodea, Diptera, Hemiptera and Neuroptera also occurred on flowers. Known or likely pollinators include bees (Hymenoptera: Apidae, Halictidae and Megachilidae) and scarab beetles (Coleoptera: Scarabaeidae). These plant species appear to have generalist pollination systems, with the exception of species of Grewia L., which appear to be pollinated primarily by bees. A provisional plant–pollinator food web is presented for the eleven species of trees and shrubs which flower during the rainy season.

Diet Composition of Western Derby eland (Taurotragus Derbianus Derbianus) in the Dry Season in a Natural and a Managed Habitat in Senegal using Faecal Analyses

The dietary composition of the western Derby eland (Taurotragus derbianus derbianus), a critically endangered antelope, was investigated using microhistological analyses of faeces. Samples were collected in the Niokolo Koba National Park, the refuge of the last wild population, and in the Bandia wildlife reserve, where the animals foraged on natural and supplementary food. Leaves, shoots of woody plants, and fruits were the three major components at both sites. They formed 98.8% of diet volume in the wild and 77.5% in the Bandia Reserve where supplementary food reduced the consumption of natural components but maintained the total content of major components together with supplement at 99.2%. Other components such as forbs and grasses appeared in low proportions, generally below 5% of the mean volume. Leaves of Boscia angustifolia, Grewia bicolor, Hymenocardia acida, and Ziziphus mauritiana, and fruits of Acacia spp. and Strychnos spinosa were identified as part of the diet in the wild. In the Bandia Rese...

Anthelmintic screening of Sub-Saharan African plants used in traditional medicine

Aim of study This study screened for anthelmintic activity of plant species traditionally used in the treatment of intestinal parasites and their symptoms in Sub-Saharan Africa in an effort to confirm their local use and aid in the search for new compounds since resistance is a growing concern. Materials and methods Aqueous and organic extracts of 33 plant parts from 17 plant species traditionally used in the treatment of intestinal infections in Sub-Saharan Africa were evaluated for their anthelmintic activity. This activity was assessed using a standard motility assay against a levamisole resistant strain of the nematode Caenorhabditis elegans. Results and conclusions Anthelmintic activity was confirmed in 12 plant species. Of these, eight showed strong evidence of activity ( p < 0.0001), one exhibited moderate evidence of activity ( p < 0.001), three demonstrated weak evidence of activity ( p < 0.05), and five plants showed no evidence of activity. The eight species with the strongest evidence of activity were Acacia polyacantha, Anogeissus leiocarpus, Bridelia micrantha, Cassia sieberiana, Combretum nigricans, Grewia bicolor, Strychnos spinosa and Ziziphus mucronata. In only two cases, Anogeissus leiocarpus and Cassia sieberiana, anthelmintic activity has been previously confirmed. The activity demonstrated against the levamisole resistant strain of Caenorhabditis elegans and the presence of molecules in these plants known or suspected of having a broad spectrum of activity provide support for further study of these plants and their compounds as possible treatments for parasitic worm infections.

Growth response of woody species to elephant foraging in Mwea National Reserve, Kenya

AbstractThe African elephant (Loxodonta africana) is known to greatly affect the structure and dynamics of vegetation. In Mwea National Reserve, elephants foraged mainly on Acacia ataxacantha and Grewia bicolor out of the five most preferred woody species. However, out of the five preferred woody species, only Grewia virosa and G. bicolor showed a positive association between their fresh use and past elephant use. All the five selected woody species showed high coppicing response after foraging, with the highest coppice growth rates recorded for Acacia brevispica and lowest for Grewia tembensis. The mean heights of woody species utilized by elephants were highest for A. brevispica and lowest for G. bicolor. The mean heights of coppices emerging after utilization by elephants were not significantly different for A. ataxacantha but were significantly shorter in the rest of the foraged species. Elephants avoided the coppices of many other woody species notably C. africana, A. tortilis, A. mellifera, Combretum aculeatum among others in the reserve. The objective of this study was to understand the capacity of woody species to recover after utilization by elephants and feeding response of elephants to new woody species re‐growth; a cycle that would define the dynamics of food resources and elephant population within the reserve.

Composition of Woody Species in a Dynamicforest–woodland–savannah Mosaic in Uganda: Implications for Conservation and Management

Forest-woodland-savannah mosaics are a common feature in the East African landscape. For the conservation of the woody species that occur in such landscapes, the species patterns and the factors that maintain it need to be understood. We studied the woody species distribution in a forest-woodland-savannah mosaic in Budongo Forest Reserve, Uganda. The existing vegetation gradients were analyzed using data from a total of 591 plots of 400 or 500 m2 each. Remotely sensed data was used to explore current vegetation cover and the gradients there in for the whole area. A clear species gradient exists in the study area ranging from forest, where there is least disturbance, to wooded grassland, where frequent fire disturbance occurs. Most species are not limited to a specific part of the gradient although many show a maximum abundance at some point along the gradient. Fire and accessibility to the protected area were closely related to variation in species composition along the ordination axis with species like Cynometra alexandri and Uvariopsis congensis occurring at one end of the gradient and Combretum guenzi and Lonchocarpus laxiflorus at the other. The vegetation cover classes identified in the area differed in diversity, density and, especially, basal area. All vegetation cover classes, except open woodland, had indicator species. Diospyros abyssinica, Uvariopsis congensis, Holoptelea grandis and all Celtis species were the indicator species for the forest class, Terminalia velutina and Albizia grandbracteata for closed woodland, Grewia mollis and Combretum mole for very open woodland and Lonchocarpus laxiflorus, Grewia bicolor and Combretum guenzi for the wooded grassland class. Eleven of the species occurred in all cover classes and most of the species that occurred in more than one vegetation cover class showed peak abundance in a specific cover class. Species composition in the study area changes gradually from forest to savannah. Along the gradient, the cover classes are distinguishable in terms of species composition and vegetation structure. These classes are, however, interrelated in species composition. For conservation of the full range of the species within this East African landscape, the mosaic has to be managed as an integrated whole. Burning should be varied over the area with the forest not being burnt at all and the wooded grassland burnt regularly. The different vegetation types that occur between these two extremes should be maintained using a varied fire regime.

The diet of kudus in a mopane dominated area, South Africa

The composition of the plant species eaten by kudu (Tragelaphus strepsiceros) determines the diet quality, which impacts on kudu condition and mortality levels. The yearround diet composition of kudus in the Limpopo Province, a mopane (Colophospermum mopane) dominated area, was determined by faecal analysis. The most important dietary plant species were Colophospermum mopane, Grewia bicolor, Terminalia prunioides, Tinnea rhodesiana, Boscia albitrunca and Combretum apiculatum, with C. mopane comprising on average 39.2 % of diet per month. Small amounts of herbs, grasses and seeds made up the remaining part of the diet. The contribution of C. mopane in the diet was negatively correlated with precipitation. Colophospermum mopane was consumed, irrespective of its high condensed tannin load (5.2–9.8 % DW) for the majority of the months. No seasonally significant differences were detected for modelled kudu diet crude protein, tannin or phenol concentrations. Colophospermum mopane showed significant seasonal differences with lowest values of protein, tannin and phenols in the late wet season. Surprisingly, crude protein concentrations were positively correlated with high levels of tannins and phenols for C. mopane. The diet of kudus comprised of significantly more species during the wet season compared to the dry season. Diet diversification, instead of protein maximization, seems a potential tool to satisfy protein requirements while reducing potential toxic effects associated with a high intake of secondary compounds. A significant positive correlation was therefore detected between the tannin concentration of C. mopane leaves and the number of plant species in the diet.

The mineral scoring technique and evaluation of indigenous browse species as natural mineral phytocentres for goats in African rangelands.

The utilization and evaluation of indigenous browse species as natural mineral phytocentres for goats was examined by the combined use of mineral concentrations, mineral scores, browse accessibility and abundance in the Ankole rangeland, Uganda. The species Grewia bicolor and Carissa edulis with > 140% mineral scores and > 70% accessibility were the most valuable mineral phytocentres and were the victims of overgrazing. Acacia albida and Acacia abyssinica with > 130% mineral scores but < 30% browse accessibility were valuable for the cut-and-carry feeding system. Species mineral scores at average and maximum dietary recommendations were < 60%, highlighting the mineral insufficiency of range browse for high-performance goats. Mineral supply potential was highest (35.0%) in the genus Acacia and lowest (5.3%) in Dichrostachsys. Browse accessibility was < 35%, in 69.2% of species. Acacia hockii was the most abundant species (24.5%) but had the lowest mineral score (17.7%). Browse species (90-100%) were deficient in Fe, Mn, Cu and Zn. The combined use of mineral concentrations and mineral scoring technique was superior to the use of mineral concentrations alone in defining mineral adequacy, deficiency and supply potential, making the mineral scoring technique a valuable tool in browse management.

Woody vegetation spatial patterns in a semi-arid savanna of Burkina Faso, West Africa

Spatial patterns of woody individuals were studied in a semi-arid savanna of West Africa located in Burkina Faso at and around 14° 12′ N and 2° 27′ W. The study was based upon a 10.24 ha plot within which individuals were mapped. Spatial pattern analysis was carried out using second order characteristics of point processes as K functions and pair correlations. The overall density amounted to 298 individuals ha-1. The most abundant species were Combretum micranthum G. Don., Grewia bicolor Juss. and Pterocarpus lucens Lepr. Anogeissus leiocarpus (D.C.) G. et Perr. was also an important constituant of this vegetation type, owing to its taller stature. Clumped spatial distributions were identified for all species except for two, for which complete spatial randomness (CSR) was found (including P. lucens, a dominant woody plant). No regular pattern was found even when tall individuals were considered alone. Aggregation dominates interspecific relationships, resulting in multispecific clumps and patches. The overall aggregation pattern was constituted by two different structures. A coarse-grain pattern of ca. 30–40 m was based on edaphic features, and expresses the contrast between sparse stands on petroferric outcrops and denser patches on less shallow soils. A finer-grain pattern made of clumps ca. 5–10 m wide, with no obvious relation to pre-existing soil heterogeneity. There was no overall pattern for saplings (between 0.5 m and 1.5 m in height) irrespective of species, and thus no obvious common facilitation factor. For species with a high recruitment level there was no significant relationship between mature adult and saplings. The only case of clumped saplings with randomly distributed adults was found in P. lucens. However, this cannot be unequivocally interpreted as density dependent regulation since the existence of such a process was not consistent with the spatial distribution of dead P. lucens individuals (victims of the last drought). The mean density around dead P. lucens was lower than around surviving ones, indicating that the last drought tended to reinforce clumping rather than promote a regular pattern of trees. Spatial pattern analysis yielded no evidence supporting a hypothesis of stand density regulation through competition between individuals. Other processes, as surface sealing of bare soils or insufficient recruitment, may play a more important role in preventing a savanna-like vegetation from turning into denser woodlands or thickets.

Influence of woody plant cover on dietary selection by goats in an Acacia senegal savanna of East Africa

Seasonal effects of woody plant cover on dietary selection and nutrition of goats were evaluated in an Acacia senegal savanna in Kenya during the dry season and wet season in 1982. Treatment paddocks were established in light, moderate, and heavy woody plant densities with 13, 31 and 47% total canopy cover, respectively. Grass and grasslike species, particularly Cenchrus ciliaris, Sporobolus pellucides, Eragrostis caespitosa, Digitaria macroblepharia and Chloris roxburghiana dominated goat diets in the early dry season. Browse, particularly Solanum incanum, Grewia bicolor, Acacia mellifera, Acacia senegal and Commiphora africana, were abundant in the diets of goats from August through November in the moderate and heavy woody covered paddocks. Acacia senegal pods were the major source of feed for goats in July and August. Crude protein concentration exceeded requirements of goats throughout the period of study. Organic matter digestibility of the goat diets was lowest in moderate and heavy woody plant conditions in the late dry season. When contemplating bush removal of woody plants (e.g. for tsetse fly control), consideration should be given to the role that large Acacia trees can play in stabilizing protein intake of goats and other domestic or wild browsers. By allowing goats simultaneous access to protein-rich, pod-producing areas and also high caloric grassland areas, pastoralists can diversify diet selection and stabilize nutrient intake. Cutting large Acacia trees for firewood and charcoal is particularly detrimental to the nutritional ecology of goats and perhaps other browsing herbivores.

Pharmacological activities of Grewia bicolor roots

Intraperitoneal administration of the ethanol extract of Grewia bicolor root (300 mg kg ) to rats in early pregnancy ( +1 – 4 days) did not affect the number of conception sites, but significantly increased resorption. In late pregnancy (+19–20 days), the extract (300 mg kg ) did not affect duration of the gestation period; however, 400 mg kg was lethal to all mother rats. The active compound, apparently a peptide, exerted a serotonin-like effect on rat uterus, rat fundus and rabbit jejunum. All these effects were abolished by methysergide. A transient serotonin-like rise in cat blood pressure was produced by the active fraction and this effect was also blocked by cyproheptadine.

Investigation of Grewia bicolor juss

Grewia bicolor is a small tree, parts of which are used in Sudanese traditional medicine for treating pustulent skin lesions, internally on indication of a delayed afterbirth and sometimes as a tranquilizer. A phytochemical investigation of Grewia bicolor gave the following results: the petroleum ether extract afforded β-sitosterol and β-sitosterol- and triterpene esters, and the triterpenes lupeol and betulin. The methanol extract afforded: β-sitosterol-glucoside and three alkaloids, harman, 6-methoxyharman and 6-hydroxyharman. The latter is the main alkaloid. The methanol extract shows activity against gram-positive and gram-negative organisms and causes a strong contraction of the isolated rat uterus which can be blocked by methysergide.

Some Measurements on the Water Relations of Baobab Trees

A variety of simple measurements were made on Baobab trees (Adansonia digitata) near Kibwezi, Kenya, to gain some information on their water economy. Water loss from cut shoots was compared with that of eight other woody species growing in the same region. The Baobab was found to be among the most effective at controlling its water loss. Daily shrinkage of the trunks was measured, giving an estimate of c. 400 litres daily water deficit when the trees are in leaf. Seasonal shrinkage indicates a loss of up to 1500 litres of water during dry periods. An attempt was made to determine root distribution. Measurements on exposed roots show that they are relatively shallow (down to c. 1.8 m), but are spread out to a distance greater than the heights of the trees. Such an extensive shallow root system is probably the best adapted to exploiting the low annual rainfall, most of which falls in the form of infrequent heavy downpours. ALTHOUGH THE BAOBAB is one of the most familiar trees in the drier parts of Africa, very little work has been done on its ecology or physiology. The distribution of the species is fairly well documented; it occurs in the semi-arid areas south of the Sahara, where the rainfall is in the range 150 to 1500 mm (with the greater part of the distribution below 800 mm), and from sea level to 1250 m in altitude (G. E. Wickens, pers. comm.). Its range extends right across the continent south of the Sahel region, as well as into east, central, and southern Africa. It is of considerable ecological importance, providing food for a wide range of animals, and also acts as an important source of water for both man and beast during conditions of drought. The baobab is of local economic importance as a producer of edible fruits and leaves, and as a source of fiber. Because of their great size and bizarre shapes, baobabs are often the most prominent tree species where they occur. They are the subject of many local legends. Although numerous attempts have been made to determine the ages of individual trees (Hobley 1922, de Villiers 1951, Swart 1963), only one paper seems to have been published dealing specifically with the ecology of this species (Owen 1974). The present study examines the role of water relations in the baobab's physiological ecology. The methods used consist of very simple measurements made in the field over a period of one year. Although the results must be rather provisional at this stage, they do at least provide some quantitative data on the water economy of this species. THE SITE AND VEGETATION All the measurements were made on trees in the 1Present address: Biology Department, The University, Southampton S09 5NH, England. vicinity of Masalani Camp, 25 km east of Kibwezi, Kenya (38.10E, 2.30S), at an altitude of 670 m. The vegetation of the area is similar to the bushland described by Lind and Morrison (1974) as occurring in the Tsavo National Park which adjoins the study area. Pratt and Gwynne (1977) refer to this community as 'dry thorn-bushland' occurring in their 'Eco-climatic zone V.' Where the vegetation is undisturbed, the trees and shrubs form three strata: Up to 3 m there is a dense impenetrable thicket formed by Acacia mellifera, A. senegal, Boscia coriacea, Combretum exalatum, Commiphora boiviniana, Grewia bicolor, and G. villosa; between 3 and 8 m approximately there is a stratum of scattered trees with an open canopy. The main species present are Acacia tortilis, Commiphora africana, C. baluensis, C. campestris, Delonix elata, and Sterculia rhynchocarpa; and the third layer consists of occasional emergent Adansonia digitata trees which are mostly 20-25 m in height. Although they are very prominent, these trees are relatively infrequent, perhaps not more than 10 per km2. They are remarkably uniform in size, so most of them may be about the same age. Of the 21 specimens measured, 16 were standing in undisturbed vegetation. In the case of the other five, the surrounding natural woody vegetation had been cleared, and had been replaced by herbaceous species characteristic of disturbed habitats. With the exception of Acacia tortilis and Boscia coriacea, nearly all the woody species lose their leaves during the long dry season from May to October. The baobabs spend only four months of the year in leaf. In the area studied, the leaves were shed in midFebruary 1978 and did not re-appear until mid-Octo-

Influences de la sécheresse de l'année 1972 sur la strate ligneuse

The effects of the 1972 drought were particularly marked upon the tree layer on the IBP study site of Fété Olé, Sénégal. The period at which trees normally come into leaf was delayed, leaf production was strongly decreased, and the trees kept their leaves for a shorter time than usual. Few trees bore fruits or seeds and fruit and seed production was also very much smaller than it is usually the case. Many trees died, but mortality rates varied widely according to species, location and age. The commonest species can be classed as follows, according to their decreasing resistance to drought : Boscia senegalensis, Grewia bicolor, Balanites aegyp-tiaca, Commiphora africana, Acacia Senegal and Guiera senegalensis.

Description de la végétation

The vegetation of the Fété Olé study area is typical of the sahelo-soudanian floristic domain, as conceived by Aubréville (1949). The number of species is low. Some 101 phanerogams have been recorded on the 1 Km2 reference quadrat. Most of these species are annual therophytes which complete their vegetation cycle within a 2-3 month period. Using the Roux and Roux (1957) technique of processing the quantitative data gathered in the field, 8 different types of vegetation («ecological groupings ») are recognized within this apparently homogenous savana. The density of trees averages 133/ha, most of them belonging to only four species : Guiera senegalensis, Balanites aegyptiaca, Grewia bicolor and Commiphora africana. For each of these species, data are given on the frequency of the various age-categories. Young Commiphora are conspicously scarce, probably owing to recent human interference. The existence of shallow depressions where water temporarily accumulates during the rains exerts a major influence upon vegetation structure and particularly upon the density of trees.