2647 research outputs found
Sort by
Experimental prosopis management practices and grassland restoration in three Eastern African countries
Get PDFThis research article was published in the CABI Agriculture and Bioscience volume 4, Article number: 21, 2023Woody species have been introduced in many parts of the world to provide economic benefits, but some of those
species are now among the worst invaders, causing widespread economic and environmental damage. Management
of woody species to restore original ecosystem services, such as biodiverse grassland that can provide fodder and
sequester carbon, are needed to limit the impacts of alien species. However, the best management methods, i.e., the
most economically efficient and effective way to remove trees and the most effective way to restore or rehabilitate
the cleared land, are not developed for many species. In Eastern Africa, prosopis (Prosopis julifora) has invaded large
areas of savanna and grassland, thereby affecting, among other things, fodder and water for livestock, access to dry
season grazing lands and ultimately pastoral livelihoods. We tested three prosopis treatments (manual uprooting
and cut stump and basal bark herbicide application) in combination with three incremental restoration interventions
(divots, divots + mulching, divots + mulching + grass seed sowing). The three-year study was replicated in Ethiopia
(Afar National Regional State), Kenya (Baringo county) and Tanzania (Moshi district). Prosopis survival and vegeta-
tion development, both diversity and biomass, were recorded. The prosopis treatments were all highly effective
(between 85 and 100% tree mortality in almost all cases), but the two treatments that involved the complete removal
of the aboveground biomass (manual and cut stump) yielded a more productive and more diverse vegetation than
the treatment that killed the trees standing (basal bark). Compared to the effect of prosopis removal, the effect of
restoration interventions on vegetation composition was small, indicating that most species re-established from the
soil seed bank. The results show that it is possible to restore land previously invaded by prosopis. Despite the differ-
ent rates of vegetation establishment and variation in species composition, the restoration interventions resulted in
vegetation that in some cases contained a substantial fraction of perennial grasses. The method chosen to control
prosopis depends on the availability of resources, including herbicides, and the need to remove rootstocks if the
intention is to plant crops
Honeybees’ foraging patterns and their relation to honey antimicrobial activity
Get PDFA Dissertation submitted in partial fulfillment of the requirements for the Master’s in Biodiversity and Ecosystem Management of the Nelson Mandela African Institution of Science and TechnologyHoneybees’ existence is highly influenced by the availability of their preferred foraging plants.
This study assessed honeybees’ foraging patterns and their relationship to honey antimicrobial
activity in Same District-Kilimanjaro, during the short and long rainy seasons of 2021/2022. The
quadrats of 5 x 5 m (shrubs and forbs) nested with 1x1 m (grasses) were established along four
transects of 5 km distance each to assess plant diversity and foraging patterns. The agar well
diffusion method was employed for the antimicrobial assay. There was a significant difference in
plant diversity between the rainy seasons (t = 2.60, p = 0.01 and t = 2.27, p =0.03). Grewia bicolor,
Terminalia brownii, Ziziphus mucronata, Combretum schumannii, and Cordia monoica were the
most visited plants by 2761, 2528, 1966, 1163, and 662 visits, during the short rain season. During
the long rainy season, Acacia mellifera, Hoslundia opposita, Ocimum bacilicum, and Acalypha
fruticosa were the most visited by 1638, 788, 340, and 38 visits. Honey harvested during the short
rain season had higher antimicrobial activities with zones of inhibition ranging between 10 mm -
19 mm. Besides, the most susceptible microorganisms were Escherichia coli and Staphylococcus
aureus. The plant leaf extracts of T. brownii, C. schumannii, and H. opposita exhibited higher
antimicrobial activities against tested microorganisms. Significant differences were observed in
antimicrobial activities among honey (F= 28.5, p = <0.001) and plant extracts (F= 15.9, p <0.001).
A strong correlation was observed in antimicrobial activities between honey harvested during the
short rainy season with T. brownii (r= 0.836, p = 0.078) and C. monoica (r = 0.732, p = 0.159).
Honeybees’ foraging patterns vary among the bloomed plant species across the rainy seasons; thus,
honey’s antimicrobial potential is highly influenced by floral sources and the harvesting season
A Survey of Machine Learning Modelling for Agricultural Soil Properties Analysis and Fertility Status Predictions
Get PDFThis research article was published by Preprints (www.preprints.org) 2023The problem of low soil fertility and limited research in agricultural data driven tools, may lead to
low crop productivity which makes it imperative to research in applications of high throughput computational
algorithms such as of machine learning (ML) for effective soil analysis and fertility status prediction in order
to assist in optimal soil fertility management decision-making activities. However, difficulties in the choice of
the key soil properties parameters for use in reliable soil nutrients analysis and fertility prediction. Also,
individual ML algorithms setbacks and modelling expert implementation procedures subjectivity, may lead to
exploitation of worst fertility level targets and soil fertility status targets classification models performance
reported variations. This paper surveys state-of-affair in ML for agricultural soil nutrients analysis and fertility
status prediction. Prominent soil properties and widely used classical modelling algorithms and procedures
are identified. Empirically exploited fertility status target classes are scrutinized, and reported soil fertility
prediction model performances are depicted. The three pass method, with mixed method of qualitative content
analysis and qualitative simple descriptive statistics were used in this survey. Observably, the frequently used
soil nutrients and chemical properties were organic carbon, phosphorus, potassium, and potential Hydrogen,
followed by iron, manganese, copper and zinc. Predominant algorithms included Random Forest, and Naïve
Bayes, followed by Support Vector Machine. Model performances varied, with highest accuracy 98.93% and
98.15% achieved by ensemble methods, and the least being 60%. Interdisciplinary ML related researchers may
consider using ensemble methods to develop high performance soil fertility status prediction models
Distribution, characterization and propagation methods for conservation and utilization of oyster nuts telfairia pedata in Tanzania
Get PDFA Thesis submitted in Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Life Sciences of the Nelson Mandela African Institution of Science and TechnologyOyster nut (Telfairia pedata) is a native East African climber, growing naturally or planted
in association with tall trees Tanzania (including Zanzibar island), Kenya and Uganda. Plot less sampling method within different land use (farmlands, homesteads, and along
riverbanks) was used to understand the spatial distribution of oyster nuts across elevation and
rainfall gradients and a cross-sectional survey using semi-structured questionnaire was
conducted on 346 respondents to assess the utilization and conservation status of oyster nuts
in northern Tanzania. In addition, phylogenetic analysis were used to assess the genetic
variability of oyster nuts collected from the study location and lastly developing local
propagation methods for the production of oyster nut seedlings for farmers in northern
Tanzania. The findings on the spatial distribution of oyster nuts indicated that more oyster nut
plants grow in higher elevations and areas with higher rainfall. The findings on utilization
and conservation status of the oyster nuts reveal that about 21% of respondents used oyster
nuts for cooking with other staple foods while (18%) claimed that the nuts are used by
pregnant and lactating mothers for medicinal and breast milk stimulation and nine percent
indicated that the nuts are used for ritual and cultural devotions. Also, respondents within the
36-50 age groups reported the greatest diversity of uses of oyster nuts were (51%) compared
with those aged below 36 years old (21%). The findings on genetic analysis suggest that the
oyster nut (Telfairia pedata) is the only specie that exists in Tanzania with similarity of >99%
to known accessions as deposited in the National Center for Biotechnology Information
(NCBI). Although the accessions were obtained from different districts in Northern Tanzania,
their close genetic similarity indicates that they might have originated from the same parents
and were introduced to other sites through cultivation by human interventions. The findings
on propagation methods for the production of oyster nut seedlings indicate that mother plant
topsoil and Nitrogen, Phosphorus and Potassium fertilizer levels and mother plant topsoil and
cow manure are the best media for the propagation of oyster nuts using stem cuttings. The
study concludes that oyster nuts offers multiple benefits to farmers and is the only species
that exist in Tanzania. The study recommends: (i) Promote the multipurpose and only oyster
nut plant that exist in Tanzania through workshops and seminars to contribute to food
security and biodiversity conservation; (ii) mother plant topsoil and NPK or cow manure are
the most suitable soil mixture for raising oyster nuts from stem cuttings; and (iii) Research
institutions can take an interest in both in-situ and ex-situ long-term monitoring trends of
oyster nuts (Telfairia pedata) distribution as it is the only specie that exists in the country
Insurance Ccompanies portfolio optimisation with possibilities of recovery after ruin
Get PDFA Dissertation Submitted in Partial Fulfilment of the Requirements for the Degree of Doctor of Philosophy in Mathematical and Computer Sciences and Engineering of the Nelson Mandela African Institution of Science and TechnologyThis dissertation, is about a study on insurance companies that have experienced ruin but have
a possibility of recovery from ruin. The study has proposed a perturbed mathematical model,
analysed and used it for modelling the portfolio of insurance companies with possibilities of re covery after ruin. Return on investment and refinancing have been used as approaches for over coming ruin. The model was analysed for various cases of possibilities of recovery after ruin in
the closed interval [0, 1]. The basic perturbed classical risk process was later compounded by
refinancing and return on investment. The Hamilton-Jacobi-Bellman and Integro-Differential
Equation of Volterra type were obtained. The Volterra Integro-Differential Equation for sur vival function of an insurance company was converted to a third order ordinary differential
equation and later converted into a system of first order ordinary differential equations which
was solved numerically using the fourth order Runge-Kutta method. The results indicate that
the return on investment plays a vital role in reducing ultimate ruin and that as the possibility
of recovery for insurance companies increases, the return on investment reduces ruin much
faster. Also, the survival function increases with the increasing intensity of the counting pro cess but decreases with an increase in the instantaneous rate of stock return and return volatility.
Because an insurance company faces more risks, these results also suggest that insurance com panies should increase their counting process since doing so will help the insurance companies
in servicing more customers
Interactive effects of dragonfly larvae andBacillusthuringiensisvar.israelensison mosquito ovipositionand survival
Get PDFThis research article was published in the Ecosphere Volume 14, Issue 9 September 2023The biological larvicide Bacillus thuringiensis var. israelensis (Bti) is used worldwide to control reproduction of mosquitoes in freshwater habitats. However, its impact on the ecosystem including nontarget species is often unclear. In addition, it is unknown how Bti larvicide may interact with local mosquito predators to shape oviposition site selection of mosquitoes. We used an outdoor mesocosm experiment to investigate the effects of realistic concentrations of the bio-larvicide Bti on Culex oviposition, larval density, survivorship, and on densities of nontarget species. We also manipulated the complexity of the community by manipulating the presence of dragonfly larvae as a predator. Culex oviposition was unaffected by Bti but the larvicide effectively reduced larval density and survivorship in all treatments. Bti did not affect nontarget insects but stimulated phytoplankton density at the expense of lower herbivore density. The presence of dragonfly larvae in mesocosms did not reduce Culex oviposition or larval sensitivity to Bti. We conclude that Bti may effectively reduce the density and survivorship of Culex quinquefasciatus mosquitoes in this part of East Africa, but possibly at the cost of higher phytoplankton densities. Bti-treated mesocosms were not more or less attractive for mosquitoes, suggesting that its application would not alter their oviposition behavior in the field
Integrating contact tracing and whole- genome sequencing to track the elimination of dog-mediated rabies: An observational and genomic study
Get PDFThis research article was published in the Elife, 2023Background:
Dog-mediated rabies is endemic across Africa causing thousands of human deaths annually. A One Health approach to rabies is advocated, comprising emergency post-exposure vaccination of bite victims and mass dog vaccination to break the transmission cycle. However, the impacts and cost-effectiveness of these components are difficult to disentangle.
Methods:
We combined contact tracing with whole-genome sequencing to track rabies transmission in the animal reservoir and spillover risk to humans from 2010 to 2020, investigating how the components of a One Health approach reduced the disease burden and eliminated rabies from Pemba Island, Tanzania. With the resulting high-resolution spatiotemporal and genomic data, we inferred transmission chains and estimated case detection. Using a decision tree model, we quantified the public health burden and evaluated the impact and cost-effectiveness of interventions over a 10-year time horizon.
Results:
We resolved five transmission chains co-circulating on Pemba from 2010 that were all eliminated by May 2014. During this period, rabid dogs, human rabies exposures and deaths all progressively declined following initiation and improved implementation of annual islandwide dog vaccination. We identified two introductions to Pemba in late 2016 that seeded re-emergence after dog vaccination had lapsed. The ensuing outbreak was eliminated in October 2018 through reinstated islandwide dog vaccination. While post-exposure vaccines were projected to be highly cost-effective (1657 per death averted) and by maintaining rabies freedom prevents over 30 families from suffering traumatic rabid dog bites annually on Pemba island.
Conclusions:
A One Health approach underpinned by dog vaccination is an efficient, cost-effective, equitable, and feasible approach to rabies elimination, but needs scaling up across connected populations to sustain the benefits of elimination, as seen on Pemba, and for similar progress to be achieved elsewhere
Does variation in plant diversity and abundance influence browsing intensity in black rhinos?
Get PDFA project report submitted by African Journal of Ecology Volume 61, Issue 3 September 2023Variations in forage availability, selection and preferences can lead to intense foraging competition and depletion of food consequently lowering diet quality and population performance of black rhino species. This study investigated seasonal variations in rhino diet, foraging, preference and browsing intensity and how this is influenced by plant diversity and availability in Mkomazi National Park (MKONAPA). Fifty-eight square grids were randomly selected in each season, and plots were laid for vegetation assessment during wet and dry seasons in the sanctuary. Browsed species by rhinos were compared with rhino feeding data from fourteen rhino range areas within Africa. More than 85% of species edible in MKONAPA were similar to those in rhino range areas. Acalypha ornata, Grewia similis and Commiphora africana were highly utilised specie in both seasons. Diversity and abundance of consumed browses decreased towards the dry season while browsing intensity increased with forage preference in both seasons and was prominent when browse availability was low in dry seasons. Our study established seasonal variation in dietary composition, browsing intensity and preferences for black rhinos. We suggest establishing nutritional composition of preferred forages, assessing density of competitor browsers, translocating excess rhinos or expanding the sanctuary to meet the recommended ecological carrying capacity
Maize stover transfers from maize fields to banana-based agroforestry homegardens and the corresponding nutrient flows in central-northern Tanzania
Get PDFA research article was submitted to Tropical Forests Volume 6 - 2023Maize (Zea mays) stover produced in the drier lowland areas on the volcanic foot slopes of Mount Kilimanjaro serves as an important additional fodder for smallholder zero-grazed dairy cattle farming in the humid highland areas of the region. The obtained cattle manure is used to replenish nutrients and manage soil fertility in banana-based agroforestry homegardens of the highlands, which contributes significantly to sustaining crop production, thus food security and the livelihoods of the community. The study aims to provide a preliminary evaluation of the amounts of stover removed from smallholder maize-based fields in the lowlands and the subsequent nutrient flows to the banana-based agroforestry homegardens of the highlands. In 54 smallholder maize fields selected at random from 11 villages in the Hai and Siha districts of the Kilimanjaro region, we conducted an agronomic survey to record the types and amounts of fertilizer used, plant spacing at harvest, and maize stover biomass yield. Most of the surveyed maize-based fields received inadequate nutrient inputs, which were limited to mineral nitrogen alone if any. Of the surveyed fields, 16.7% received recommended amounts of 74 kg N ha–1 by the Ministry of Agriculture, 46.3% sub-optimal amounts and 37.0% did not receive fertilizer at all. Plant density was only 50% of the recommended population density. While this was only a preliminary study on nutrient flows between maize and banana-based agroecosystems, our findings demonstrated that potassium exports via harvested banana bunches exceeded the inputs in the homegardens. We conclude that (i) soil fertility management techniques, preferably integrated soil fertility management, suitable for small-scale maize production in the lowlands should be formulated while optimizing plant density to increase production, (ii) maize-based agroforestry farming system adapted to drier conditions to deal with windstorm and soil erosion problems in the lowlands is urgently needed, and (iii) wider and more detailed research on nutrient flows between maize and banana-based agroecosystems should be conducted to document their respective soil nutrient balances and the sustainability of such practice
Prevalence of chronic obstructive pulmonary disease and associated factors among smallholder fish vendors along coastal areas in Tanzania
Get PDFThis research article was published by BMC Pulmonary Medicine in 2023Background In Tanzania little is known about how the respiratory system of small-holder fish vendors is affected by
occupational exposure to biomass smoke and other associated factors. This study assessed the prevalence of lung
obstruction and associated factors among small-holder fish vendors along coastal areas in Tanzania.
Methods A cross-sectional descriptive study was conducted in Bagamoyo and Kunduchi fish markets along coastal
areas of Tanzania. Environmental air pollutant levels and composition were measured using a hand-held device. A
standardized questionnaire was used to assess respiratory symptoms while EasyOne spirometer was used to test for
lung function among small-holder fish vendors. Chronic Obstructive Pulmonary Disease (COPD) was defined as FEV1/
FVC below the lower limit of normal. Data were analyzed using STATA Version 17. Descriptive statistics was performed
and logistic regression analysis was used to determine factors that are associated with poor lung function presented
as crude and adjusted odds ratio and their 95% confidence intervals.
Results A total of 103 participants were included in the study who were predominantly males 82 (79.6%). The
participants’ mean age was 35.47 (±8.77 SD) years. The hourly average concentration levels of PM1, PM2.5, PM10, and
CO exposure during fish frying were 653.6 (±206.3 SD) μg/m3
, 748.48 (±200.6 SD) μg/m3
, 798.66 (±181.71 SD) μg/m3
and 62.6 (±12.3 SD) ppm respectively which are higher than the WHO recommended limits. The prevalence of COPD
was found to be 32.04% (95% CI 0.23–0.42). Most of the participants reported respiratory symptoms like coughing,
wheezing, sputum production and breathlessness during performing their daily activities.
Conclusion Findings suggest that three out of ten participants had COPD and the major environmental air
pollutants (PMs and CO) concentration levels were too high, suggesting that occupational exposure to biomass
smoke may be a risk factor. This calls for effective approaches to reduce exposure and prevent known acute and
chronic respiratory diseases that are associated with such exposure to air pollutants. Also the study calls for follow up
or cohort studies to be conducted in this are