Vegetation Studies of Selected Islands and Adjacent Mainland on Lake Kariba, Zimbabwe.

An IES Working Paper on the vegetation of islands adjacent to Lake Kariba, Zimbabwe.The objective of this study was to classify and describe the vegetation of selected islands on Lake Kariba. A total of forty-six islands were surveyed. Two hundred and eleven samples were classified into twenty-six vegetation types. The types were described in terms of their location, floristic composition andfactors that determine or influence them. Woodlands consisted of ten types: Colophospermum mopane woodland, Colophospermum mopane-Combretum apiculatum woodland, Colophospermum mopane mixed woodland, Combretum apiculatum mixed woodland, Mixed Combretum woodland, Combretum elaeagnoides mixed woodland, Julbernardia globiflora woodland, Ficus sycomorus woodland, Acacia nilotica woodland and Acacia nigrescens-Afzelia quamensis mixed woodland. Thickets and woodland thickets consisted of four types: Karomia tettensis thicket, Diospyros quiloensis thicket, Combretum celastroides woodland thicket and Guibourtia conjugata woodland thicket. Shrublands consisted of five types: Colophospermum mopane shrubland, Mundulea sericea shrubland, Croton menyhartii shrubland, Pteliopsis myrtifolia shrubland and Indigofera tinctoria shrubland. Grasslands consisted of seven types: Melinis repens wooded grassland, Panicum repens grassland, Aristida rhiniochloa grassland, Aristida adscensionis grassland, Heteropogon contortus grassland, Urochloa trichopus wooded grassland and Eragrostis viscosa wooded grassland. Populations of large herbivores, especially elephants are having a negative impact on vegetation structure and species composition on some of the islands. The influence of soil texture in determining species composition is also significant with most thickets and woodlands occurring on sands. Twenty-nine years of isolation from the mainland has not had a significant influence on species richness and composition of the vegetation of the islands.Funding for the publication of this study was provided by the Canadian International Development Agency (CIDA) Harare, Zimbabwe through the CIDA/MET/UZ Programme

Ecological degradation in cities: impact of urban agriculture In Harare, Zimbabwe

A journal article on the impact on the environment of urban agriculture in Zimbabwe.The effect of the increasingly widespread practice of urban agriculture in the City of Harare on the natural biodiversity was investigated. Vegetation surveys noting species presence-absence and abundance were undertaken in seven field areas, identifying the components of the natural vegetation of both the clay soil-type areas developed on basic rock, and the sandy soil-type areas developed on granite, that typify the city. Change brought about by the increasingly widespread practice of urban agriculture was determined, and knock-on effects for other aspects of the city's ecology were investigated. Most open space areas in Harare are vlei land. Detrended Correspondence Analysis (DCA) illustrated significant differences in the species composition of uncultivated vlei areas with distance from the vlei channel, reflecting change in the water-logging conditions of the soil. A higher diversity of faunal species, and larger species count, prior to cultivation was also noted. The effects of cultivation on the vegetation were a change in species composition (with the natural vegetation being replaced by mainly alien arable weeds), the loss of the spatial diversity in species presence and dominance, a significantly reduced ground cover, and a loss of habitat diversity. The implications of these changes for the amenity value of the city environment is discussed. The need for a more sensitive management of open-land areas within Harare, while the possibility of their conservation as areas of viable natural ecological diversity is still available, is highlighted

Responsiveness of Dichrostachys cinerea to seasonal variations in temperature and rainfall in central Namibia

Woody plants provide natural archives of climatic variation which can be investigated by applying dendroclimatological methods. Such studies are limited in Southern Africa but have great potential of improving our understanding of past climates and plant functional adaptations in the region. This study therefore investigated the responsiveness of Dichrostachys cinerea to seasonal variations in temperature and rainfall at two sites in central Namibia, Waterberg and Kuzikus. Dichrostachys cinerea is one of the encroacher species thriving well in Namibia. A moving correlation and response function analysis were used to test its responsiveness to seasonal climatic variations over time. Dichrostachys cinerea growth rings showed relationships to late summer warming, lasting up to half of the rainy season. The results also revealed that past temperatures had been fluctuating and their influence on growth rings had been intensifying over the years, but to varying extents between the two sites. Temperature was a more important determinant of ring growth at the drier site (Kuzikus), while rainfall was more important at the wetter site (Waterberg). Growth ring responsiveness to rainfall was not immediate but showed a rather lagged pattern. We conclude that D. cinerea differentially responds to variations in rainfall and temperature across short climatic gradients. This study showed that the species, due to its somewhat wide ecological amplitude, has great potential for dendroclimatological studies in tropical regions

Short-Term Influence of Fire on Herbaceous Composition, Diversity and Grass Biomass Production in Semi-Arid Savanna Woodland in Windhoek, Namibia

Abstract A co mparative study on short term in fluence of fire on herbaceous composition and grass biomass production was conducted in a semi-arid savanna woodland in Windhoek, to assess differences in herbaceous composition and grass biomass production after a late dry season fire. The study revealed that herbaceous composition and grass cover differ significantly between the burned and unburned areas. Grass cover differed significantly (p< 0.001) between the burned and unburned areas. Fire removes aging grass materials, growth inhib itors and moribund hence, enhancing the vitality grasses. There were no significant differences in species richness (t = -1.402, p > 0.05), species diversity (t = -1.391, df = 28, p > 0.05), grass biomass production (t = 1.724, p > 0.05) and forb densities (t = 0.361, p > 0.05) between the burned and unburned areas..The study findings suggested that short term fire does have a significant impact on grass cover and herbaceous dominance and insignificant impact on grass biomass production, forb densities, species richness and diversity in short term, but fire impact on these plant attributes also depend on the intensity of fire and time frame

Human Appropriation of Net Primary Productivity and Rural Livelihoods: Findings From Six Villages in Zimbabwe

The African land system is undergoing rapid change, and novel approaches are needed to understand the drivers and consequences of land use intensification. Human Appropriation of Net Primary Productivity (HANPP) is a powerful indicator of land use intensity, but has rarely been calculated at high spatial resolutions. Based on data from six villages in Zimbabwe, we present a novel method of calculating HANPP at community and household scales, and explore to what extent household wealth is related to NPP appropriation. HANPP at the village scale was higher than expected from previous studies, ranging from 48% to 113% of potential NPP. Loss of NPP through land use change accounted for the greater proportion of HANPP in four of the six villages, but NPP embodied in livestock feed, firewood and construction materials also contributed significantly to total appropriation. Increasing household wealth was associated with increasing appropriation of NPP in harvested resources, but not with loss of potential NPP through land use change. Our results indicate that land use intensity is currently underestimated in smallholder farming areas of southern Africa. High-resolution HANPP calculations based on field data offer an effective new approach to improving understanding of land use intensification in complex socioecological system

Vegetation structure and effects of human use of Dambos ecosystem in northern Mozambique

Original research articleThe Niassa National Reserve (NNR) is the most extensive conservation area in Mozambique and the third largest in Africa, encompassing 42,000 km2 of endemic miombo vegetation. Dambos wetlands occur within the wooded grassland and grassland vegetation of NNR and provide a wide range of Ecosystem Services (ES), including life support for animal species, regulation of water flow and prevention of soil erosion. It also generates income for the livelihoods of local communities by providing land for agriculture and harvesting of non-timber products. The dynamics of these ecosystems is poorly understood despite the contribution of the dambos to global biodiversity and ES. This research is the first preliminary assessment of the vegetation structure and composition of six dambos within NNR, selected using Google Earth, MODIS satellite images and an exploratory field visit. Field data collection was performed using a two-stage systematic sampling approach, along transect lines of 100 10m (0.1 ha), perpendicular to the dambos' flow. Square plots of 0.25m2 were established for grass survey within the transects where grass vegetation was measured, counted and identified. Data were analyzed with R software. The sociological position of each species was analyzed with regard to the vertical structure while for horizontal structure, the abundance, dominance, frequency and Importance Value Index (IVI) were determined. In order to understand the differences between dambos, evenness (H) and reciprocal of Simpson's heterogeneity index (Hill's N2) were calculated. Principal Coordinates Analysis (PCoA) and Cluster Analysis were also used to characterize the surveyed species communities. A total of 58 transects (5.8 ha) and 336 subplots were assessed, recording 110 woody and 73 grass species, respectively. The most common tree species were Vitex doniana, Burkea africana, Syzygium cordatum and Annona senegalensis, while for grass vegetation the most abundant species were Andropogon eucomus and Helictotrichon turgidulum. According to the IVI, the most dominant tree and shrub species were V. doniana, Pseudolachnostylis maprouneifolia, A. senegalensis and S. cordatum. Homogeneity (Hill's N2 ¼18.92) and evenness (H¼ 4.27) were, on average, low in all dambos. Dambo 2 was the most heterogeneous (Hill's N2 ¼18.21) while dambo 1 was the least heterogeneous (Hill's N2 ¼ 5.71). Dambo 6 was most equitable (H¼ 1.35) whereas dambo 2 the least equitable (H¼ 3.72). Using species abundance and based on PCoA and cluster analysis, four main groups of dambos were identified based mainly on the water gradient, with data variation captured by the first three axes reaching almost 83%. The p-value (0.42), suggested no significant differences between species communities in the dambos, and thus, human disturbances appear not to be enough to modify dambos microenvironment. Accordingly, the results suggest that human activities, at this level, do not necessarily affect the structure and diversity of dambos in the NNR. The results also suggest that the species A. senegalensis, Combretum psidioides, Crossopteryx febrifuga, Protea nitida, P. maprouneifolia and S. cordatum can be used as indicator dambo species in NNR, with high likelihood of occurrenceinfo:eu-repo/semantics/publishedVersio

The charcoal trap: Miombo forests and the energy needs of people

<p>Abstract</p> <p>Background</p> <p>This study evaluates the carbon dioxide and other greenhouse gas fluxes to the atmosphere resulting from charcoal production in Zambia. It combines new biomass and flux data from a study, that was conducted in a <it>miombo </it>woodland within the Kataba Forest Reserve in the Western Province of Zambia, with data from other studies.</p> <p>Results</p> <p>The measurements at Kataba compared protected area (3 plots) with a highly disturbed plot outside the forest reserve and showed considerably reduced biomass after logging for charcoal production. The average aboveground biomass content of the reserve (Plots 2-4) was around 150 t ha^-1, while the disturbed plot only contained 24 t ha^-1. Soil carbon was not reduced significantly in the disturbed plot. Two years of eddy covariance measurements resulted in net ecosystem exchange values of -17 ± 31 g C m^-2y^-1, in the first and 90 ± 16 g C m^-2in the second year. Thus, on the basis of these two years of measurement, there is no evidence that the <it>miombo </it>woodland at Kataba represents a present-day carbon sink. At the country level, it is likely that deforestation for charcoal production currently leads to a per capita emission rate of 2 - 3 t CO₂y^-1. This is due to poor forest regeneration, although the resilience of <it>miombo </it>woodlands is high. Better post-harvest management could change this situation.</p> <p>Conclusions</p> <p>We argue that protection of <it>miombo </it>woodlands has to account for the energy demands of the population. The production at national scale that we estimated converts into 10,000 - 15,000 GWh y^-1of energy in the charcoal. The term "Charcoal Trap" we introduce, describes the fact that this energy supply has to be substituted when woodlands are protected. One possible solution, a shift in energy supply from charcoal to electricity, would reduce the pressure of forests but requires high investments into grid and power generation. Since Zambia currently cannot generate this money by itself, the country will remain locked in the charcoal trap such as many other of its African neighbours. The question arises whether and how money and technology transfer to increase regenerative electrical power generation should become part of a post-Kyoto process. Furthermore, better inventory data are urgently required to improve knowledge about the current state of the woodland usage and recovery. Net greenhouse gas emissions could be reduced substantially by improving the post-harvest management, charcoal production technology and/or providing alternative energy supply.</p

Evidence that the Human Pathogenic Fungus Cryptococcus neoformans var. grubii May Have Evolved in Africa

Most of the species of fungi that cause disease in mammals, including Cryptococcus neoformans var. grubii (serotype A), are exogenous and non-contagious. Cryptococcus neoformans var. grubii is associated worldwide with avian and arboreal habitats. This airborne, opportunistic pathogen is profoundly neurotropic and the leading cause of fungal meningitis. Patients with HIV/AIDS have been ravaged by cryptococcosis – an estimated one million new cases occur each year, and mortality approaches 50%. Using phylogenetic and population genetic analyses, we present evidence that C. neoformans var. grubii may have evolved from a diverse population in southern Africa. Our ecological studies support the hypothesis that a few of these strains acquired a new environmental reservoir, the excreta of feral pigeons (Columba livia), and were globally dispersed by the migration of birds and humans. This investigation also discovered a novel arboreal reservoir for highly diverse strains of C. neoformans var. grubii that are restricted to southern Africa, the mopane tree (Colophospermum mopane). This finding may have significant public health implications because these primal strains have optimal potential for evolution and because mopane trees contribute to the local economy as a source of timber, folkloric remedies and the edible mopane worm

Ecological Thresholds in the Savanna Landscape: Developing a Protocol for Monitoring the Change in Composition and Utilisation of Large Trees

BACKGROUND: Acquiring greater understanding of the factors causing changes in vegetation structure -- particularly with the potential to cause regime shifts -- is important in adaptively managed conservation areas. Large trees (> or =5 m in height) play an important ecosystem function, and are associated with a stable ecological state in the African savanna. There is concern that large tree densities are declining in a number of protected areas, including the Kruger National Park, South Africa. In this paper the results of a field study designed to monitor change in a savanna system are presented and discussed. METHODOLOGY/PRINCIPAL FINDINGS: Developing the first phase of a monitoring protocol to measure the change in tree species composition, density and size distribution, whilst also identifying factors driving change. A central issue is the discrete spatial distribution of large trees in the landscape, making point sampling approaches relatively ineffective. Accordingly, fourteen 10 m wide transects were aligned perpendicular to large rivers (3.0-6.6 km in length) and eight transects were located at fixed-point photographic locations (1.0-1.6 km in length). Using accumulation curves, we established that the majority of tree species were sampled within 3 km. Furthermore, the key ecological drivers (e.g. fire, herbivory, drought and disease) which influence large tree use and impact were also recorded within 3 km. CONCLUSIONS/SIGNIFICANCE: The technique presented provides an effective method for monitoring changes in large tree abundance, size distribution and use by the main ecological drivers across the savanna landscape. However, the monitoring of rare tree species would require individual marking approaches due to their low densities and specific habitat requirements. Repeat sampling intervals would vary depending on the factor of concern and proposed management mitigation. Once a monitoring protocol has been identified and evaluated, the next stage is to integrate that protocol into a decision-making system, which highlights potential leading indicators of change. Frequent monitoring would be required to establish the rate and direction of change. This approach may be useful in generating monitoring protocols for other dynamic systems