Southern Savannas Research Articles

Patterns and Teleconnection Mechanisms of Extreme Precipitation in Ethiopia during 1990–2020

The occurrence of extreme precipitation events always leads to a mass of disasters. In this study, based on daily precipitation data from 20 meteorological stations in Ethiopia, we performed a detailed analysis of patterns and trends of ten extreme precipitation indices during 1990–2020. Our study revealed that different topographic conditions on the Ethiopian Plateau, Ethiopian savanna and Ethiopian desert resulted in great differences in patterns and trends of extreme precipitation. Notably, extreme precipitation intensity indices (Rx1day, Rx5day, SDII) and amount indices (R95pTOT) showed significant downward trends in the eastern desert (averagely −1.0 mm/year, −3.0 mm/year, −0.25 mm day−1/year, −6.0 mm/year) and upward trends in the northern plateau and southern savanna (averagely 0.3 mm/year, 0.4 mm/year, 0.05 mm day−1/year, 3.0 mm/year). These implied that extreme precipitation events decreased in the eastern desert and increased in the northern plateau and southern savanna during the past thirty years. Annual trends of the CDD index were upward (0.5 to 1.9 days/year) in most of Ethiopia while those of the CWD index were close to zero in most of Ethiopia, indicating that Ethiopia faced a longer duration of drought in the past thirty years. Moreover, we revealed that the local mean temperature, local mean precipitation, Southwest Asian summer monsoon and West African summer monsoon have significant impacts on the intensity, amount and duration of extreme precipitations in Ethiopia.

Assessment of Maize (Zea mays) Genotypes for Seed Metrics, Agronomic Performance, Yield and Nutritional Content in the Southern Savanna Agro-ecological Zone of Nigeria (Wukari as Case Study)

Maize is ranked as one of the cereal crops with high yield potential globally and may be considered very important for countries like Nigeria, where there is an increasing demand for food to meet the demand of its teeming population. Five varieties of maize (Sammaz 52, M1217, M1155, Oba 98 and Oba super II) obtained seed companies and mostly grown in Wukari were evaluated during the 2020/2021 cropping seasons for yield, agronomic performance, seed metrics and nutritional quality at the Research and Teaching Farm of the Federal University Wukari, Taraba State. Having four replications, the experiment was set up using Randomized complete Block Design (RCBD). Obtained data on agronomic characters, yield and nutrient qualities revealed significant differences among the varieties for days to tasseling, silking, grain yield, nutritional content, number of nodes, ear height (cm), hundred seed weight (g), number of seed rows, seed length at P>0.05. Height at matirity showed significant difference, with Oba98 having the highest (195.25 cm) value. M1217 recorded superiority (24.95g) over the other varieties for 100 seed weight. Laboratory Analysis was conducted to determine the essential amino acid and nutritional content of the five maize varieties. There was a significant variation in the crude protein content of the five varieties with the SAMMAZ52 having the highest value (13.14%). Oba 98 recorded highest essential amino acid such as Methionine (2.39), Lysine (2.33) and Tryptophan (1.43) over the other varieties assessed.

Local perception of ecosystem services and their conservation in Sudanian savannas of Burkina Faso (West Africa)

ContextIn Burkina Faso, Sudanian savannas are important ecosystems for conservation of plant diversity. Due to desertification and insecurity, population migration from the North has increased human density and anthropogenic pressure on southern savannas. This study aims to investigate knowledge of local populations on ecosystem services (ES) and perception of their conservation.MethodIndividual semi-structured interviews about knowledge on ES and ecosystem conservation issues were conducted. Informants were selected according to sociocultural groups and sex in three areas of different land use intensity: the communal area of Dano (CAD), the Total Wildlife Reserve of Bontioli (TWRB) and the Game Ranch of Nazinga (GRN). The use value and vulnerability index of each plant species were determined. A cluster analysis and a principal component analysis were carried out to identify the particular knowledge of different ethnic groups.ResultsOverall, 163 plant species were cited for fifteen ES. Provisioning services were most frequently cited (100%), regulating services second most frequently (92.47%). Entire plants were exclusively used for ES with non-material benefits (protection against wind, for shading, soil fertility, erosion prevention, tourism and religion). The ten species contributing most to ES provision were Vitellaria paradoxa, Parkia biglobosa, Diospyros mespiliformis, Adansonia digitata, Lannea microcarpa, Faidherbia albida, Khaya senegalensis, Afzelia africana, Ficus sycomorus, Pterocarpus erinaceus. Seven of them were identified as highly vulnerable. Around GRN, migrants and natives shared the same knowledge, while migrants in TWRB used the ES only to a small extent due to restricted contact with the native population. Migrants and natives of GRN had more knowledge on tourism and crafts services while the natives of CAD and TWRB made use of the services that sustain the quality of the agricultural land and meet their primary needs. To reduce further degradation, different communities suggested unanimously raising awareness of the importance of biodiversity and ecosystem conservation. The most quoted motivations to preserve ecosystems were vegetation sustainability and village development.ConclusionThis study documented important local knowledge-based information to guide cultivation of local multipurpose species and initiation of communities to practice best management strategies for sustainable conservation of biodiversity.

Small rodent communities (Muridae) in Gabonese savannas: species diversity and biogeographical affinities

Abstract The study contributes to the knowledge of species composition and biogeographical affinities of savannas rodent in Gabon. Unlike small rodents in Gabonese forests, there is little data on the diversity of small rodents in Gabonese savannas. The diversity and distribution of rodent murid communities was studied in four different types of savanna in Gabon: Coastal Basin (South-West), Lopé/Okanda (in the Center), Batéké Plateaux (Southeastern) and Ngougnié/ N’yanga (in the South). A total of 428 individuals representing six species were captured over 11,920 trap nights. Trap success was highly variable (2.2–6.9 %). The most abundant species were Mus minutoides (69%) followed by Lemniscomys striatus (21.5%). Indices of species richness varied from 2 to 5 and diversity (Shannon and Weaver) was low in the four savannas with the highest value at Ngougnié/N’yanga (H′ = 1.2). Species distributions show that Gabonese savanna small rodents conform to four distribution types, with one species known from Zambesian savannas exhibiting austral affinities (Pelomys campanae: occurs in three southern savannas). This new information provides important insight into the biogeography of small rodents at a local and regional level. Moreover, the correspondence analysis highlighted an influence of local ecological factors on population abundance.

The vectoring of Starmerella species and other yeasts by stingless bees in a Neotropical savanna

Abstract In Brazilian savannas, stingless bees are associated with yeast communities composed mainly of Starmerella species. This study aimed to establish the distribution of yeasts associated with the bee species Frieseomelitta varia, Scaptotrigona aff. postica, Scaptotrigona polysticta, Tetragonisca angustula angustula, Melipona compressipes manaosensis and Melipona scutellaris in northern savannas and the importance of yeasts in the resource partitioning of bees. We collected 380 bees from six species, which were individually placed in Petri plates containing rich medium for 15 min. Yeasts were then isolated, resulting in the identification of 54 species, 48 of which were ascomycetous, while six were basidiomycetous. Torulaspora delbrueckii was the most frequently isolated yeast species in this study, followed by Pichia membranifaciens, Starmerella apicola, Pichia kluyveri, Starmerella meliponinorum and Starmerella bombicola. The total number of Starmerella species identified showed that these species are prevalent in association with these stingless bees. These communities differ from stingless bee-associated yeasts found in the southern savannas of Brazil. Although stingless bees are generalist foragers, there are some yeasts showing high prevalence in only one bee species, resulting in differences in niche breadth that may point to a role of yeasts in the resource partitioning of bees in Brazilian savannas.

Comparative Study of Maize Agronomics Performance under low Nitrogen Soil Availability, in Southern Savanna of DR Congo


 
 
 To determine the growing and yield performance of low nitrogen tolerant maize varieties under fertilized and unfertilized conditions, a study was conducted at the Mvuazi Research Center. Nine varieties were tested with and without fertilizer using the micro-dosing method, following the randomized complete block design with two factors. The results showed a difference among varieties in both crop conditions. The average yield with fertilizer was higher than the yield without fertilizer. The varieties LNTP-W C4 and LNTP-Y C7 registered 5.9 t/ha and 3.6 t/ha respectively under fertilized crop conditions and 7.14t/ha and 7.12t/ha under unfertilized crop conditions. Thus, using Low-N can minimize production costs by improving the productivity of soils low in Nitrogen typical of conditions of the southwestern savanna.
 KEY WORDS: LOW NITROGEN SOIL, LNTP, MAIZE PRODUCTION, FERTILIZER, SAVANNA, INERA-DRC
 
 

Combining ability and heterosis in egusi-melon <i>Citrullus lanatus</i> (Thumb.) Matsum and Nakai

This study was carried out to evaluate the genetic potential of seven egusi-melon genotypes for seed weight and its components following the diallel mating scheme. Seven parents were selected from among 28 genotypes obtained from indigenous farmers in five ecological zones (forest, derived savanna, southern, northern and Sudan savanna) of Nigeria. The experiment was laid out in a completely randomized block design with four replications. Specific combining ability variance was of greater importance than general combining ability variance in the inheritance of all the traits under study. Okwe-2-IM x KTGO-GMB was the best combiner for number of pods and pod weight per plant while KOGI-NITN x MOKWA-NG was the best combiner seed weight per plant. Positive and highly significant (P<0.01) heterosis was recorded among crosses for number of primary vines, number of pods and seed production efficiency per plant indicating their importance in hybrid development for improved yield.

Comparative Study of Maize Agronomics Performance Under Low Nitrogen Soil Availability, in Southern Savanna of Dr Congo

To determine the growing and yield performance of low nitrogen tolerant maize varieties under fertilized and unfertilized conditions, a study was conducted at the Mvuazi Research Center. Nine varieties were tested with and without fertilizer using the micro-dosing method, following the randomized complete block design with two factors. The results showed a difference among varieties in both crop conditions. The average yield with fertilizer was higher than the yield without fertilizer. The varieties LNTP-W C4 and LNTP-Y C7 registered 5.9 t/ha and 3.6 t/ha respectively under fertilized crop conditions and 7.14t/ha and 7.12t/ha under unfertilized crop conditions. Thus, using Low-N can minimize production costs by improving the productivity of soils low in Nitrogen typical of conditions of the southwestern savanna.

Differential Response of Three Carrot Genotypes to Different Levels of Organic and Inorganic Fertilizer Application in Southern Derived Savanna Zone of Nigeria

This study was conducted at landmark University during the period of 2015 and 2016 to assess the differential response of three Carrot genotypes to different levels of Organic and Inorganic fertilizer application in Southern Savanna Zone. The experiment was conducted using a Randomized Complete Block Design with three replications. Data collected on leave number, fresh leave weight, plant height and fresh root weight were subjected to analysis of Variance. Different between means were partitioned using Duncan Multiple Range test at 5% probability level (p = 0.05). The study revealed that at application of 36.8kg/ha of NPK 15:15:15 and 1t/ha of organic manure the three carrot genotypes responded differently and significantly for fresh root yield. However, there was no significant differential response to organic manure application for leaf number, but there was significant differential response under the application of 71.60kg/ha of NPK 15:15:15. All the three Carrot genotypes responded differently and significantly at application of 1t/ha of organic manure for plant height. At all levels of both Organic and Inorganic manure applications, all the three Carrot genotypes responded differentially for root yield either significant or non-significant at different levels of application. Highest Carrot root yields (40.87t/ha, 41.48t/ha and 41.58t/ha) were recorded by Varieties, ALBAKA NOMA and ROHAMA NOMA under the organic manure regime. Future study should focus on the identification of required level of manure for optimal production of individual Carrot genotypes rather than general recommendation for all the Carrots genotypes.

Prevalence of Cutaneous Leishmaniasis in Districts of High and Low Endemicity in Mali.

Historically the western sahelian dry regions of Mali are known to be highly endemic for cutaneous leishmaniasis (CL) caused by Leishmania major, while cases are rarely reported from the Southern savanna forest of the country. Here, we report baseline prevalence of CL infection in 3 ecologically distinct districts of Mali (dry sahelian, north savanna and southern savanna forest areas). We screened 195 to 250 subjects from 50 to 60 randomly selected households in each of the 6 villages (four from the western sahelian district of Diema in Kayes region, one from the central district of Kolokani and one from the southern savanna district of Kolodieba, region of Sikasso). The screening consisted of: 1] A Leishmanin Skin Test (LST) for detection of exposure to Leishmania parasites; 2] clinical examination of suspected lesions, followed by validation with PCR and 3] finger prick blood sample to determine antibody levels to sand fly saliva. LST positivity was higher in the western district of Diema (49.9%) than in Kolokani (24.9%) and was much lower in Kolondieba (2.6%). LST positivity increased with age rising from 13.8% to 88% in Diema for age groups 2–5 years and 41–65 years, respectively. All eight PCR-confirmed L. major CL cases were diagnosed in subjects below 18 years of age and all were residents of the district of Diema. Exposure to sand fly bites, measured by anti-saliva antibody titers, was comparable in individuals living in all three districts. However, antibody titers were significantly higher in LST positive individuals (P<0.0001). In conclusion, CL transmission remains active in the western region of Mali where lesions were mainly prevalent among children under 18 years old. LST positivity correlated to higher levels of antibodies to sand fly salivary proteins, suggesting their potential as a risk marker for CL acquisition in Mali.

The role of forest expansion and contraction in species diversification among galagos (Primates: Galagidae)

AbstractAimHere, I investigate galagid diversification and current distribution in the context of major climatic and geological events in sub‐Saharan Africa. Given their widespread distribution and presence in a large range of diverse habitats, galagids represent an excellent group to investigate the role of forest contraction and expansion on biological diversification in sub‐Saharan Africa.LocationSub‐Saharan Africa (Afrotropical Region).MethodsI assembled a supermatrix including 53 nuclear loci and three mitochondrial markers for 94% of the galagid species currently recognized. Bayesian and maximum likelihood methods were used to infer phylogenetic relationships and times of divergence within the family. Ancestral ranges were estimated using several methods, including ‘BioGeoBEARS’ and rasp.ResultsPhylogenetic analyses corroborated previous results regarding the evolutionary history of this family: (1) early origin of the family soon after the Eocene‐Oligocene boundary; (2) dwarf galagos (Galagoides spp.) represent a polyphyletic group with two well‐defined clades, one in central‐west Africa and one in the east; and (3) divergences within galagids are relatively old with most genera already present by the Late Miocene. The biogeographical analysis indicates central African origins and subsequent expansion to the east in the Early‐Middle Miocene. An expansion to the northern and southern savannas occurred between the Late Pliocene and the Middle Pleistocene.Main conclusionsThe results of this study clarify several questions related to the evolutionary history of the Galagidae in the context of sub‐Saharan African biogeography. This study suggests that galagid evolution and diversification was affected by three major climatic episodes: (1) the global cooling and forest contraction in the Early Oligocene, (2) the forest expansion and the uplift of the African rifts in the Miocene and (3) the aridification and extension of open woodlands and savannas in the Late Miocene and Plio‐Pleistocene.

Using a jumping spider fauna inventory (Araneae: Salticidae) as an indicator of their taxonomic diversity in Misiones, Argentina.

Faunistic studies, with a taxonomically complete inventory of species, provide an important source of quantitative compiled information for several and specific regions. This information can be used in diversity analysis and has great potential in setting conservation priorities. In this study, I used the relatively well known salticid spider fauna of Misiones to generate Clarke & Warwick taxonomic diversity indices. For this, information of three ecoregional salticid diversities was obtained and analyzed between Upper Parana Atlantic Forest (UPAF), Araucaria Moist Forest (AMF), and Southern Cone Mesopotamian Savanna (SCMS). Results showed differences between the three ecoregions of the province, mainly Southern savannas regarding the forests of Northern Misiones. Most species were registered in UPAF followed by AMF, however the α-taxonomic diversity of salticids was higher in SCMS than in UPAF and AMF. The β-taxonomic diversity showed that the proportions of shared species between SCMS and UPAF (or and AMF) were the lowest. The high taxonomic dissimilarity among ecoregions is an indication that the three assemblages are distant, showing a variation in their vegetation habitat and/or bioclimatic characteristics as a possible reason. The need to expand with new samples in subsampled or underexplored areas of Misiones remains essential, however this study contributes to information about biodiversity levels of salticid fauna in three ecoregions of Northeast Argentina, and will provide reference data for future studies for management plans.

A Quantitative Evaluation of the Multiple Narratives of the Recent Sahelian Regreening*

Abstract A spatial analysis is presented that aims to synthesize the evidence for climate and social dimensions of the “regreening” of the Sahel. Using an independently constructed archival database of donor-funded interventions in Burkina Faso, Mali, Niger, and Senegal in response to the persistence of drought in the 1970s and 1980s, the spatial distribution of these interventions is examined in relation to population density and to trends in precipitation and in greenness. Three categories of environmental change are classified: 1) regions at the northern grassland/shrubland edge of the Sahel where NDVI varies interannually with precipitation, 2) densely populated cropland regions of the Sahel where significant trends in precipitation and NDVI decouple at interannual time scales, and 3) regions at the southern savanna edge of the Sahel where NDVI variation is independent of precipitation. Examination of the spatial distribution of environmental change, number of development projects, and population density brings to the fore the second category, covering the cropland areas where population density and regreening are higher than average. While few, regions in this category coincide with emerging hotspots of regreening in northern Burkina Faso and southern central Niger known from case study literature. In examining the impact of efforts to rejuvenate the Sahelian environment and livelihoods in the aftermath of the droughts of the 1970s and 1980s against the backdrop of a varying and uncertain climate, the transition from desertification to regreening discourses is framed in the context of adaptation to climate change.

Projected changes in distributions of Australian tropical savanna birds under climate change using three dispersal scenarios

Identifying the species most vulnerable to extinction as a result of climate change is a necessary first step in mitigating biodiversity decline. Species distribution modeling (SDM) is a commonly used tool to assess potential climate change impacts on distributions of species. We use SDMs to predict geographic ranges for 243 birds of Australian tropical savannas, and to project changes in species richness and ranges under a future climate scenario between 1990 and 2080. Realistic predictions require recognition of the variability in species capacity to track climatically suitable environments. Here we assess the effect of dispersal on model results by using three approaches: full dispersal, no dispersal and a partial-dispersal scenario permitting species to track climate change at a rate of 30 km per decade. As expected, the projected distributions and richness patterns are highly sensitive to the dispersal scenario. Projected future range sizes decreased for 66% of species if full dispersal was assumed, but for 89% of species when no dispersal was assumed. However, realistic future predictions should not assume a single dispersal scenario for all species and as such, we assigned each species to the most appropriate dispersal category based on individual mobility and habitat specificity; this permitted the best estimates of where species will be in the future. Under this “realistic” dispersal scenario, projected ranges sizes decreased for 67% of species but showed that migratory and tropical-endemic birds are predicted to benefit from climate change with increasing distributional area. Richness hotspots of tropical savanna birds are expected to move, increasing in southern savannas and southward along the east coast of Australia, but decreasing in the arid zone. Understanding the complexity of effects of climate change on species’ range sizes by incorporating dispersal capacities is a crucial step toward developing adaptation policies for the conservation of vulnerable species.

Interannual variability of photosynthesis across Africa and its attribution

Africa is thought to be a large source of interannual variability in the global carbon cycle, only vaguely attributed to climate fluctuations. This study uses a biophysical model, Simple Biosphere, to examine in detail what specific factors, physiological (acute stress from low soil water, temperature, or low humidity) and biophysical (low vegetation radiation use), are responsible for spatiotemporal patterns of photosynthesis across the African continent during the period 1982–2003. Acute soil water stress emerges as the primary factor driving interannual variability of photosynthesis for most of Africa. Southern savannas and woodlands are a particular hot spot of interannual variability in photosynthesis, owing to high rainfall variability and photosynthetic potential but intermediate annual rainfall. Surprisingly low interannual variability of photosynthesis in much of the Sudano‐Sahelian zone derives from relatively low vegetation cover, pronounced humidity stress, and somewhat lower rainfall variability, whereas perennially wet conditions diminish interannual variability in photosynthesis across much of the Congo Basin and coastal West Africa. Though not of focus here, the coefficient of variation in photosynthesis is notably high in drylands and desert margins (i.e., Sahel, Greater Horn, Namib, and Kalahari) having implications for supply of food and fiber. These findings emphasize that when considering impacts of climate change and land surface feedbacks to the atmosphere, it is important to recognize how vegetation, climate, and soil characteristics may conspire to filter or dampen ecosystem responses to hydroclimatic variability.

Human Plague in the Southwestern United States, 1957–2004: Spatial Models of Elevated Risk of Human Exposure to &lt;I&gt;Yersinia pestis&lt;/I&gt;

Plague is a rare but highly virulent flea-borne zoonotic disease caused by the Gram-negative bacterium Yersinia pestis Yersin. Identifying areas at high risk of human exposure to the etiological agent of plague could provide a useful tool for targeting limited public health resources and reduce the likelihood of misdiagnosis by raising awareness of the disease. We created logistic regression models to identify landscape features associated with areas where humans have acquired plague from 1957 to 2004 in the four-corners region of the United States (Arizona, Colorado, New Mexico, and Utah), and we extrapolated those models within a geographical information system to predict where plague cases are likely to occur within the southwestern United States disease focus. The probability of an area being classified as high-risk plague habitat increased with elevation up to approximately 2300 m and declined as elevation increased thereafter, and declined with distance from key habitat types (e.g., southern Rocky Mountain piñon--juniper [Pinus edulis Engelm. and Juniperus spp.], Colorado plateau piñon--juniper woodland, Rocky Mountain ponderosa pine (Pinus ponderosa P.& C. Lawson var. scopulorum), and southern Rocky Mountain juniper woodland and savanna). The overall accuracy of the model was >82%. Our most conservative model predicted that 14.4% of the four-corners region represented a high risk of peridomestic exposure to Y. pestis.

BOOK REVIEW: Gordon, David M. NACHITUTI'S GIFT: ECONOMY, SOCIETY, AND ENVIRONMENT IN CENTRAL AFRICA. Madison, Wisconsin: University of Wisconsin Press. 2006.

Reviewed by: Nachituti's Gift: Economy, Society, and Environment in Central Africa Robert Ross Gordon, David M. 2006. Nachituti's Gift: Economy, Society, and Environment in Central Africa. Madison, Wisconsin: University of Wisconsin Press. xii + 301 pp. $ 60.00(cloth). The so-called "fisherman's dilemma" is a well-known problem of forms of economics that places private property at the center of management systems of the natural environment. Fishermen obviously want to conserve stocks so that next year they can continue to fish, but it may be more "rational" for them to take all they can, as they have no guarantee that some other fishermen will not do just that, so that that their refusal of income at this [End Page 118] point does not have the desired consequences in the future. The standard answers to this dilemma, in terms of the imposition of individual rights over resources ("property") cannot work in open waters, or indeed rangeland, and other forms of communal management have to be found, at least where the danger of overfishing exists. In this book, David M. Gordon describes the working out of this dilemma in the rich fisheries of the Luapula Valley, including Lake Mweru, on the border between Zambia and the Democratic Republic of Congo (Katanga Province). The book happily straddles the customary periodization in terms of the presence or absence of colonial rulers, but nevertheless the forms of political authority and technological change have had crucial consequences, at various times, for how the valley's fish have been exploited by the valley's humans. Successive rulers have seen the valley as a source of power and income. In precolonial times, it must have been just about the most thickly populated, and thus attractive, regions of the southern savanna, and came under the control of the Kazembe Lunda, in forms of rule justified by a number of myths, including that of Nachituti, a self-willed woman, whose marriage to the Kazembe Lunda legitimized their rule. Gordon analyzes this myth with care and skill, as he does the shift to colonial domination, in which the unitary valley was divided, as it has remained. It was with the introduction of colonialism that the management systems which had been developed under the aegis of the Kazembe began to break down. The various chiefs no longer had the power to hold the lagoons shut until they had given the word that fishing might begin. The successive Kazembe kings lived under British rule, while the economic power was on the Belgian side, both because fish was primarily marketed to feed the laborers on the Belgian Copper Belt—the Northern Rhodesian mines served beef, rather than fish, as protein—and because the valley was much closer to centers of Belgian power than to those of British power. As a result, the Belgians introduced large-scale mechanized fishing, run primarily by Greeks, which would, in the early 1950s, result in a major economic disaster. The mudfish mpumbu was effectively exterminated by overfishing at its spawning runs, partially because of the expatriates' motorized boats and partially because the colonial-organized elimination of crocodiles from the lake meant that larger nets could be used without being broken. A species that had made up close to half of the Union Minière's (a major copper mining company in Congo) purchases had disappeared as a commercial proposition. What this has meant, over the subsequent decades, has been a reorientation of the fishing effort toward the smaller species within the lake and the swamps. There was the increased human exploitation of species that have not suffered under the potential for overfishing, either because their spawning grounds could in general be protected or because, like the tiny chisense, their reproductive cycle was so short and so prolific that they could hardly be destroyed by heavy predation—and they may have benefited from an increase in the lake's vegetable plankton as artificial fertilizer from the surrounding hills leached into its waters. Since chisense could easily be [End Page 119] caught and traded, the result has been a shift in gender relations, as individuals previously excluded from the trade for lack of capital—in other words, women...

Effect of Balanites glabra canopy cover on grass production, organic matter and soil moisture in a southern Kenyan rangeland

A study was undertaken in Kenya's southern savanna rangelands to determine the seasonal effect of Balanites glabra canopy cover on aboveground grass biomass, grass species composition, soil organic matter and soil moisture content. The study was conducted during the period June to December 1999 in order to capture both the dry and wet season effects. The grass biomass in the sub-canopy zone (2-4m from tree trunk) was found to be significantly higher than in the mid-canopy (0-2m from tree trunk) and open grassland zones (4-6m from tree trunk) during the dry season. However, the difference between the sub-canopy and the open grassland was not significant during the wet season, implying that the role of a tree canopy in enhancing grass biomass is greater during the dry than the wet season. Variations in percent grass species composition from the mid-canopy to the adjacent open grassland were observed, indicating that while B. glabra canopy cover favours certain grass species, other species find the micro-climatic conditions under the canopy unfavourable. Soil organic matter in the mid-canopy zone was significantly higher than in the sub-canopy and adjacent open zones during both dry and wet season. Although the sub-canopy zone exhibited significantly higher soil moisture content than the mid-canopy and open grassland zones during the dry season, the difference between the sub-canopy and the adjacent open grassland during the wet season was not significant, suggesting that the tree canopy influence on soil moisture is more pronounced in the dry than the wet season.

Growth and biomass allocation of shrub and grass seedlings in response to predicted changes in precipitation seasonality

Anthropogenic emissions contribute to an annual 0.5% increase in atmospheric CO2. As global CO2 levels increase, regional precipitation patterns will likely be altered. Our primary objective was to determine whether a reduction in summer precipitation or an increase in winter/spring precipitation, predicted by global climate change models, will favor the establishment of C4 grasses or C3 shrubs in southern savannas. Our secondary objective was to determine how defoliation and microsite light availability interact with altered precipitation regimes to influence grass and shrub seedling growth and biomass allocation patterns. Seedlings of 3 shrub species (Prosopis glandulosa var. glandulosa, Acacia berlandieri, and A. greggii var. wrightii) and 3 grass species (Aristida purpurea var. wrightii, Setaria texana, and Stipa leucotricha) were watered based on probable changes in precipitation in a CO2 enriched atmosphere (0.6, 0.8, and 1.0 current ambient summer precipitation and 1.0, 1.15, and 1.30 current winter/spring precipitation). Seedlings were defoliated at 3 levels (non-defoliated, single defoliation, and repeated defoliation) within 2 levels of microsite light availability (100 and 50% ambient). Defoliation significantly reduced total shrub and grass seedling biomass. Reducing light availability decreased shrub seedling root:shoot ratio, but total biomass was not significantly affected. Grass seedling biomass and root:shoot ratio decreased when light availability was reduced. Changing the seasonality of precipitation by reducing summer rainfall or increasing winter/spring rainfall did not significantly influence growth or biomass allocation of grass and shrub seedlings in a semiarid savanna. Microsite variations in defoliation intensity and light availability influence seedling growth and biomass allocation more than changing seasonality of precipitation. Shrub and grass seedling establishment and growth on semiarid rangelands are already limited by summer precipitation, so a further reduction as proposed by climate change models will have a limited impact on seedling dynamics.

Influence of environment on protein and oil contents of soybeans seed (Glycine Max (L.) Merril)

An attempt was made to study the magnitude of environmental variability on protein and oil contents of six genetically diverse soybean genotypes under three environments represented by three locations in Nigeria (Zaria in Northern Guinea Savanna, Jos in Pseudo Savanna and Mokwa in Southern Savanna) for two years (1996 and 1997). Significant genotypic location and location x genotype x year effects were observed for protein content while genotypic and location x genotype effects were significant for oil contents. Significant genetic differences in protein content occurred among genotypes, locations and between years, whereas significant genotypic differences in oil content was observed. Bossier and TGX849-313D out yielded in protein content. Protein content in Mokwa and Zaria were higher than that of Jos while protein content in Year 2 (1997) was higher than Year 1 (1996). Oil content remained similar irrespective of location and year. Jos is in a dry cool environment compared with Mokwa which is humid and hot and Zaria which is dry and hot. Environmental factors exerted greater influence more on the protein content than oil content of tropical soybean seeds. High temperature tended to increase protein content with little or no effect on oil content. There was positive significant association between protein and oil contents under Jos environment in 1997 whereas the association was negatively significant under Mokwa environment. Therefore, selection for protein and oil contents among soybean genotypes for further improvement is possible due to large variability present. Variations in protein and oil contents were due to differences in location. Changes in climatic factors resulting from yearly cultivation of soybean in different locations can influence protein content. Key Words: correlation analysis, genotype, Glycine max, oil, protein [Global Jnl Agric Sci Vol.1(1) 2002: 27-32]