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- ItemLong -Term Vegetation Dynamics over the Bani River Basin as Impacted by Climate Change and Land Use(2015-07-29) Traore, Souleymane SidiThis study investigated the long-term trends in vegetation and rainfall and the extent and rate of vegetation change over the Bani river Basin at multiple spatial and temporal scales in relation to local and regional drivers. Monthly 8-km Normalized Difference Vegetation Index (NDVI) time-series data from 1982 to 2011 was derived from 10-day Satellite Pour l’Observation de la Terre vegetation product (SPOT-VGT) at 1-km (1998-2011) and 15-day GIMMS (Global Inventories Monitoring and Modelling Systems) at 8-km satellite data (1982-2006). Gridded rainfall data at 8-km grid resolution was created from 40 meteorological stations and complemented with Tropical Rainfall Measurement Mission (TRMM) data. A Mann Kendall (MK) trend analysis was used to determine the trend for each dataset using monthly and annual time-series. This analysis produced some indicators like Kendall’s tau, p-value and Theil-Sen. The p-value estimator (p-value less than 0.07) was used in this study to show the significance of the trend. Trend analysis revealed that within the study area vegetation greening trends are mostly associated with areas where natural vegetation is still well represented. From the results 934 pixels (49% of the study area) showed a positive trend while 155 pixels (8% of the study area) showed a negative trend significant at p-value less than 0.07. During the same period rainfall had increased by about 17 mm, translating into a positive trend for almost the entire study area. Vegetation productivity in the study area is dependent on rainfall which varies greatly temporally and spatially. The linear Pearson correlation was used to estimate the relationship between NDVI and rainfall for every pixel at monthly interval for the growing season data. Comparing their long-term mean the result showed a good correlation between the two datasets with an R value of 0.98. Four (4) reference areas were used to explain and cross verify representative areas that exhibit either entirely negative MK-trends or entirely positive MK-trends over the monitoring period. These reference areas were selected based on their trend in rainfall and NDVI and their NDVI long-term departure. Free 30-meter Landsat images were acquired for the four reference areas for the following three intervals: 1984 and 1986, 1999 and 2000 and 2009 and 2010. Land Use/Land Cover (LULC) change was then quantified and the rate of land conversion was determined. LULC variables included urban, Cropland and natural vegetation (Shrublands, Steppe, Open Trees and Closed Trees). For the entire period, the class ‘Natural Vegetation’ decreased between 22.83% and 63.47% from its initial area for areas (1) and (2), while the decrease was 8.35% for area (3) and 13.39% for area (4). The class ‘Cropland’ increased for 564.86% in area (3); 62.17% in area (4); 35.79% in area (2) and 16.22% in area (1). To investigate whether there is a relationship between NDVI, rainfall and LULC change, LULC variables were correlated with long-term trend in rainfall and NDVI. The results showed there is a positive correlation between increases in rainfall and some land cover classes, while some classes such as settlements were negatively correlated with vegetation productivity trends. Croplands and Natural Vegetation were positively correlated (r=0.89) with rainfall while settlements have a negative correlation with NDVI time series trends (r=-0.57). Despite the fact that rainfall is the major determinant of vegetation cover dynamics in the study area, it appears that other human-induced factors such as urbanisation have negatively influenced the change in vegetation cover. The results provide spatially explicit and temporally good and rich information of vegetation productivity dynamics and its drivers at landscape scale. This is an important input for assessing the impact of climate change on vegetation for biophysical modelling. It also improves our knowledge of the drivers of vegetation productivity changes. The study suggests that NDVI can be useful for general vegetation cover monitoring and planning. Future studies need to also look at the effect of vegetation cover change in regard to other landscape components such as specifically population density and soil degradation.
- ItemTowards Improved Quality and Performance of Cold-Mix Asphalts for Bituminous Pavement Maintenance in Ghana(KNUST, 2023-02) Boateng, Kwadwo AppiahPremature failure and poor performance of cold-mix asphalts (CMAs) used in pothole patching and sectional repairs on bituminous roads are very common in Ghana, and yet, for a long time, the problem has remained unaddressed while the material continues to be used. There is, therefore, the need to improve the quality of cold-mix asphalts used in the country in order to achieve a more successful and durable product in road maintenance. To this end, Ghana’s Ministry of Transportation (MOT) Standard Specification for Road and Bridge Works (2007) was reviewed alongside three foreign specifications on CMAs, namely, Asphalt Institute MS 19 (1997), Chevron USA Incorporated Procedure and Nikolaides Specification (1994), to establish possible commonalities and areas of deviations that could impact the field performance of the material. Also, samples from ready-to-use CMA stockpiles at six contractor sites across the country, and failed road patches were investigated. Further, a series of dense-graded cold-mix asphalts, with simplified material proportioning ratios, were proposed and investigated for adoption and use. Lastly, potential improvement in CMA properties, using montmorillonite nanoclay filler, was explored. It was established that Ghana’s MOT Specification lacked specificity and clarity on the subject of CMAs. In the case of the other Specifications, though variations in mixture design and testing protocols existed, there appeared to be a general consensus on the use of different aggregate gradation structures that lead to high field performance. The asphalt contents of the cold-mix asphalt samples taken from the field tended to range between 3% and 6%, with emulsion mixes having the lower values. In addition, the aggregate structures of the mixes were poor, consisted essentially of single-size aggregates with uniformity coefficient values that ranged between 1 and 4. Some specimens compacted in the laboratory disintegrated during conditioning for stability and flow test, suggesting a lack of stickiness and cohesion within the compacted matrix. It, therefore, appears that the early failures characterizing cold-mix asphalts used in maintenance works in the country could be due principally to inadequate aggregate structure and low binder content of the mixes. For improved cold-mix quality, five aggregate gradation blends that meet GHA dense grading requirements, together with the corresponding emulsionto- aggregate ratio, for easy material batching in the field, have been proposed. Montmorillonite nanoclay used as filler increased the optimum bitumen content and improved the stability of the cold-mixes but resulted in significantly high flows. This suggests that their use in cold-mix asphalts has the potential to induce plastic behaviour and render the mixes more rut-susceptible, especially at high temperatures.
- ItemAgricultural Land Use Change in the Lowlands of Southern Mali under Climate Variability(KNUST, 2023-07) Traore, AlouThis research investigated agricultural land use change in the lowlands of Southern Mali under climate variability. Four supervised classification techniques, Classification and Regression Tree (CART), Support Vector Machine (SVM), Random Forest (RF) and Gradient Tree Boosting (GTB) in Google Earth Engine (GEE), were used for the image classification. An integrated Cellular Automata-Artificial Neural-Network (CA-ANN) within the MOLUSCE plugin of QGIS was used for future Land Use and Land Cover prediction. The Mann-Kendall test, Sen’s slope, Pettit-test and change-point detection analyse were applied for climate variability assessment. Monthly rainfall and mean temperature extending over a period of 61 years (1960–2020) recorded at Sikasso District were analysed. Annual rainfall varied between 800 mm to 1600 mm and annual mean temperature ranged between 25 oC to 28 oC. Seasonal rainfall ranged between 37-387 mm, March-April-May (MAM), 400-1030 mm, June-July-August (JJA), 77-577 mm September-October-November (SON) and 0-45 mm for December-January-February (DJF). Mean seasonal temperature ranged from 29 oC to 32 oC (MAM), 26.5 oC to 28.5 (JJA) oC and 26 oC to 28 oC (SON). Annual and seasonal rainfall trends increased slightly. Temperature showed a significant increase in both annual and seasonal trends. Out of 395 respondents, 79 % were of the view that annual rainfall decreased while 83 % reported mean temperature increased. Again, respondents perceived late onset rainfall (97 %), early cessation of rainfall (96 %), increased in drought (83 %) and flooding (96 %). Also, 43 % of respondents adopted new varieties to cope with climate variability. The findings showed that physical and socioeconomic driving forces had impact on terrain patterns. Over the past three decades, the study revealed that apart from cropland area which increased from 43.81 % to 52.75 %, the size of the other land uses decreased, forest cover (19.93 % - 13.93 %) shrubs (16 % - 14 %), and streams (6 % - 4 %). However, the forecast for the 2020 to 2030 predicted an increasing trend in forest cover and decreasing trend in agricultural land in the study area due to the ongoing afforestation projects. The study demonstrates the need to reinforce regional land management policies and programmes.
- ItemDevelopment of Asphalt Pavement Temperature Prediction Models for the Climatic Conditions of Ghana(2023-07) Ntramah, SimonAsphalt pavement temperature finds application in several areas of pavement engineering including pavement structural evaluation and design, asphalt mixture design, asphalt material aging characterisation, and asphalt binder grade selection. Predictive models may be used in the estimation of asphalt pavement temperature when necessary, however, such models tend to have limited transferability and applicability to other regions where the environmental conditions are significantly different from those under which the models were developed. To avoid the risk of using foreign-developed models in estimating the temperature of asphalt pavements in Ghana using local data, this research set out to develop asphalt pavement temperature prediction models applicable to the climatic conditions of the country. Two locations in the country, one within the Savannah climatic zone and the other within the Forest climatic zone, were used for the study. Mid-depth and surface asphalt pavement temperatures, along with climatic data, were collected over a 12-month period (May 2022 to April 2023) at the two study locations. The dataset was then used to develop separate asphalt pavement temperature prediction models applicable to each climatic zones. Additional pavement temperature and climatic data were also collected on separate roads within the corresponding climatic zones for model validation. When tested against some high-rated foreign-developed models, using local environmental data inputs, the locally-developed models predicted asphalt pavement temperatures that were much superior in accuracy (R2 ≥ 0.919, RMSE < 2.8 ºC) to those predicted using the best-performing foreign-based model (R2 ≤ 0.905, RMSE ≥ 3.2 ºC). The local models are, therefore, recommended for predicting mid-depth asphalt pavement temperatures in the Forest and Savannah zones of Ghana for pavement engineering purposes.
- ItemCrops-Livestock Integration as a Resilience Strategy to Climate Change in Burkina Faso(2023-07) Sanou, Charles LamoussaThis study titled addressed a topical issue of climate change and its impacts on farmers' livelihoods and the role that an integrated crop-livestock system can play in building resilient farmers and agricultural systems. The research first of all analysed historical climate (rainfall, minimum and maximum temperature) trends across three climatic zones Sudan (Dano), Sudan-Sahel (Niou) and Sahel (Dori)) at annual, seasonal and decadal scales. Climates indices computation was done using the package ClimPACT2 GUI in R software. Annual and seasonal climate were compared using the independent t-test. Decadal climate indices were subjected to a Principal Component Analysis (PCA). The research also analysed the susceptibility or sensibility of crop production and livestock health to climate change. Thirdly, the research developed and/or updated measurement tool known as Crop-Livestock Integration (CLI) indicators for a holistic characterisation of integrated croplivestock system. These indicators were developed based on the information from 589 farmers’ households and secondary data. Above ground, data were collected from 4,733 trees over a total land area of 243.2 ha (80.1 ha, 78.8 ha and 84.3 ha in Sudan, Sudan-Sahel and Sahel zones, respectively). Due to the Sahel zone's insecurity, soil data could be collected only within Sudan and Sudan-Sahel zones. In total, 120 composite soil samples were collected for this purpose and 240 other samples for soil bulk density determination. Results revealed changes in climate conditions, more pronounced in temperature variations than in rainfall. In the Sudan-Sahel and Sahel zones, a re-wetting trends was observed over the last decade supporting the re-greening hypothesis of the Sahel. Despite some positive effects of the climate indices, crop failure was the major impact of climate pejoration across iv zones. Similarly, livestock health was majorly negatively affected by climate deterioration though the resurgence of diseases due to climate change. Climate indices could explain 23.0 - 50.2 % of the variations in crop yield and an increased cases of livestock diseases occurrence by 1-9.4 units due to the deterioration in climate conditions across climatic zones. Changes in climatic conditions may also induce microbial proliferation and host susceptibility to result in the emergence, redistribution, and changes in the incidence and intensity of pest infestations. The study concluded that crop-livestock integration is underperforming in Burkina Faso and can be improved. Majority farmers (91.6 %) in the Sudan-Sahel zone are practising full crop-livestock integration, unlike the Sahel (62.3%) and Sudan (48.2%) zones. However, only 14.8%, 10.5% and 5.1 % showed the effectiveness of integration in the Sudan-Sahel, Sahel and Sudan zones, respectively. CLI was comparatively more effective in Sudan-Sahel (65.9±32.0 %) than Sahel (44.9±29.5 %) and Sudan zones (35.6±35.0 %). Integration indicators were significantly associated with farm emissions, productivity, biodiversity and soils nutrients. CLI is also a tree-based system with high sequestration potential that could significantly counterbalance the whole system emissions. However, the coverage of fodder needs is negatively associated with soils nutrients content indicating field nutrient mining if an appropriate scheme of nutrient return to the soils as manure is not set. An adequate combination of CLI components offers an opportunity to build resilient farming systems in Burkina Faso to adapt to the changing climate.
- ItemAdoption and Effects of Climate Change Adaptation, and Land Use Decision of Smallholders Farmers in the Saline Area of Sine-Saloum, Fimela Senegal(2023-07) Thiam, Habibatou IbrahimaSoil salinity expansion is one of the most severe land degradation issues confronting farmers in Senegal, particularly in coastal areas such as Fimela. With sea level rise, temperature rise, and rainfall decrease, soil salinity is increasing significantly. It has a negative impact on crop yields and farmers' livelihoods. Farmers developed land use adaptation strategies to deal with soil salinity. Nonetheless, despite adaptations, some farmers continue to complain about the negative impact of soil salinity on their outcomes. Then, this study investigates farmers' adaptation, the different factors that influence it, its implications for smallholder farmers' livelihoods, and farmers' perception of soil salinity and its impact. Data from face-to-face interviews of 288 households using the Krejci and Morgan’s formula and GPS coordinates of households and each of their farms was collected. An agent-based model was used to understand land use adaptation to soil salinity expansion by considering farmers' perceptions of soil salinity expansion under climate change for simulation. A sub-model of household decisions, crop yield, and perception of soil salinity was developed and incorporated into the model. Three scenarios were considered to simulate the interaction between household agents and landscape agents over 25 years. Farmers' adoption is influenced by their assets and sociopsychological factors like threat assessment, coping assessment, and subjective norms. Farmers in Fimela do not have maladaptation thinking that may break their willingness to adopt strategies to cope with soil salinity. The ESR model shows that farmers' adoption of strategies to cope with soil salinity has a positive impact on groundnut yields and a negative influence on food security but has no significant effect on their millet yields. These findings have been validated by the simulation results, which show that the yield difference between farmers who perceive soil salinity expansion and those who do not is significant for groundnut but not millet over 25 years. As a result, it is critical to base policies in combating soil salinity effects on providing better methods of soil salinity adaptation strategies through scientific research. Policies should support a few pilot farmers in these precise and effective strategies to trigger other farmers to follow through the village and social influence by the farmer-to-farmer approach to enable farmers access and appropriation of these new methods.
- ItemImpact of climate change and land use/land cover change on soil fertility in the cotton Basins of Côte d’Ivoire(KNUST, 2023-07) Kone, IsmailThe study assessed the impact of alterations in land use and land cover, as well as fluctuations in climate patterns, on soil fertility within the cotton-producing area of Côte d'Ivoire. The study entails evaluating how farmers perceive and cope with climate change, determining the current state of soil fertility, evaluating land suitability and management options for cotton production, and simulating the way the land in the region will be utilized and the vegetation that will cover it in the future. To evaluate smallholder farmers' perceptions of climate change adaptation options, a structured questionnaire with closed questions was used to collect data from 355 farmers located in the cotton basin of Côte d'Ivoire. The findings revealed that most respondents acknowledged the existence of climate change in the area and its detrimental impact on farmers' livelihoods, leading them to adopt coping mechanisms. To determine the status of soil fertility, the study analyzed 64 soil samples collected in 2013 and 2021 in the same fields where cotton was grown. Specifically, the analysis focused on the physical and chemical properties of the topsoil layer, ranging from 0 to 20 centimeters in depth. Between 2013 and 2021, the chemical properties of the soil (concentrations of Ca2+, Mg2+, K+, and Base Saturation (BS)) saw only a slight improvement, leaving soil fertility as a significant constraint on cotton production. Targeted, site-specific soil management is necessary to address this issue. The study evaluated soil suitability for cotton cultivation in eight villages in the Côte d'Ivoire cotton basin by characterizing two representative soil profiles (0-100 cm) per village which were described in terms of their soil chemical and physical properties. The soils were "moderately suitable" (S2) or "marginally suitable" (S3) due to poor chemical properties, such as the Sum of Basic Cations (SBC) and organic carbon (OC). The study also used Landsat images to track changes in land use and land cover (LULC) between 1998 and 2020 and predicted future LULC for 2035 and 2063 using the TerrSet software and the CA-Markov chain. From 1998 to 2020, there was a reduction in the share of forestland and Savannah with each zone decreased by -11.09 % and -21.56 % respectively at Korhogo, -14.09 % and -1.78 % respectively at Ferkessedougou, -0.33 %, and -14.8 % respectively at Boundiali, and -6.9 % and -31.33 % respectively at Mankono, while water body, cropland, and settlement/bare land increased. From 1998 to 2035, the results revealed that the share of cropland and, settlement/bare land within the department continue to increase in the study area by 4.54 % and 28.2 %, respectively at Korhogo, 5.34 %, and 10.45 % at Ferkessedougou, 14.95 %, and 0.01 % at Boundiali, and 1.12 %, and 37.04 % in the zone at Mankono. From 1998 to 2063, the results revealed that the share of cropland and, settlement/bear with the department's land could continue to increase. The findings of this study could aid in improving and optimizing soil management practices within the cotton-producing region of Côte d'Ivoire.
- ItemDrought-Heatwaves’ Dynamics with Land Use Land Cover Types under the West African Monsoon System(KNUST, 2023-08) RAGATOA, DAKÉGA SABERMAHeatwaves are prolonged periods of abnormal heat that can adversely impact human and animal well-being, public infrastructure, agriculture, wildfire occurrence and severity, and workplace efficiency. With increasing global warming, heatwaves and droughts are predicted to worsen. However, there are only a few documented cases of heatwaves in Africa, and less research in West Africa has explored the thermodynamics of heatwaves in the region. This study seeks to comprehensively investigate the dynamics of heatwaves, particularly their interaction with landatmosphere processes and droughts as compound events in three climate zones in West Africa. The research compares heatwave and heat-stress occurrences and their coincidental intensity with drought, using satellite, reanalysis, and in-situ datasets from 1981 to 2020. The study uses Cumulative Heat (CumHeat or Heatcum) and Universal Thermal Climate Index (UTCI) to measure heatwaves, Standardized Precipitation (Evapotranspiration) Index (SPI or SPEI) for drought, and Normalized CumHeat for temperature (Tmax and Tmin), UTCI, and Wet-Bulb Globe Temperature (WBGT) to examine heatwave dynamics. The study employs the ECMWF Year of Polar Prediction (YOPP) dataset to determine the main temperature advection and tendency terms that contribute to heatwaves in selected cases (2018, 2019, and 2020) covering different climate zones, from 1000 hPa, 925 hPa, to 850 hPa, and 700 hPa. The study also uses validated coupled RegCM-CLM simulation outputs initialized with soil moisture to compute SPEI and the normalized heatwave indices. The Drought-heatwave (D-HW) events from observational data showed lower frequency and intensity than the gridded dataset. The West African monsoon system is experiencing an increase in the intensity and duration of UTCI and Tmax heatwaves, mainly before or after the monsoon phase, with some occurrences during the monsoon phase. An increasing trend in the intensity and duration of heatwaves, up to 40 days, has been observed in the gridded dataset, and there is a higher likelihood of WBGT occurrence during the night. The study found that the differences in heatwave indices are primarily due to the sensitivity to moisture and wind. The intensity of heatwaves exhibits asymmetric statistical responses to moisture content deficits, particularly in the Guinea zone and some parts of Sudan (Coast of Senegal). In the Eastern part of West Africa, the opposite reaction to mid-latitudes is observed, where there is an increase in moisture before and during a high heatwave. The impact of soil moisture on heatwaves extends to the 6th level (8th level) about 0.492912 m (1.38283 m) into the soil. These findings could help improve weather forecasting, predict the impacts of heatwaves, and design adaptation strategies to reduce the vulnerability of populations to heatwaves. Additionally, the results contribute to developing more accurate and robust climate models that can better simulate the behaviour of heatwaves and their interactions with other climate variables.
- ItemLand Use Land Cover and Climate Change impacts on Agroecosystem Services Provisioning in Riverine Areas of Pendjari Reserve in Benin, West Africa(KNUST, 2023-08) MAKPONSE, DOSSA ARMANDExamining the effects of land use and land cover change (LULCC) on biodiversity loss and human wellbeing in the Pendjari Reserve, a biodiversity hotspot in West Africa that has seen human disturbances for years, is the primary goal of this study. The study employed Landsat images and utilized the Random Forest classification software to analyze the dynamics of LULC for 1998, 2007, 2013, and 2020. The expected LULC for 2035 was projected using Terset 18.21. To learn more about household socio- economics characteristics and the advantages of trees in the townships from Tanguieta and Materi, information from 361 farmers was gathered. The influence of farm size, landholding, and district on tree diversity, tree species richness, and tree abundance, were examined as their combined impacts. The study unveiled notable alterations in LULC patterns, such as a reduced wooded savannah and a rise in shrub, cropland, and fallow land. Settlement areas experienced an increase in the studied period. The predicted results indicated an imminent slight decrease in wooded savannah, increase in shrub savannah, cropland, and fallow land, as well as a reduction of settlement areas in the future. Furthermore, farmers' preferences for tree and crop associations were assessed, with Parkia biglobosa identified as the tree species with the largest mean diameter at breast height (dbh) and height. At the same time, Vitellaria paradoxa had the highest height in Materi and Tanguieta. Tree benefits played a crucial role in selecting trees for agroforestry systems, with provisioning services followed by supporting services being the most common ecosystem benefits derived by local communities. Tree-crop associations varied among the farmers. The study examined the effects of tree conservation on agricultural output in agroforestry systems within the same study region as well as the impact of climate trends on critical crop yields. Findings revealed a substantial positive (warming) trend in temperature and a decrease in rainfall. There was a general positive warming trend observed between 1981 to 2020. Results showed that the lowest temperature positively and considerably impacted maize yields, while rainfall and relative humidity adversely affected respectively negatively and positively maize yields. The minimum temperature and relative humidity had a positive and substantial impact on sorghum. The maximum temperature and relative humidity negatively impacted cotton yield, but rainfall had affected positively cotton yields. Maximum and minimum temperature positively and significantly impacted cowpea yields. The Exponential regression model indicated that soil physicochemical characteristics and distance between tree and crop were the primary variables influencing crop yields in agroforestry systems. Furthermore, the study demonstrated that the maximum carbon stored by wooded savannah was projected to be 494,198.1 Mg C ha-1 in 2050, which decreased to 387,059.4 Mg C ha-1 in 2020 and 387,047.2 Mg C ha-1 in 2035. The lowest value of carbon is projected to be sequestered from 2020 to 2035, over a period of fifteen years. The highest gain and loss of projected carbon to sequestered for the period 2020 - 2050 is 108,947 Mg C ha-1 and -57, 996 Mg C ha-1 and the period 2035 -2050 is 108878 Mg C ha-1 and -57984.6 Mg C ha-1, respectively. Conversely, the lowest gain and loss were anticipated from 2020 to 2035, with value of 845.56 Mg ha-1 and -47.52 Mg C ha-1, respectively.
- ItemEnhancing Biogas Recovery from Anaerobic Co-digestion of Human Excreta and Food Waste using Response Surface Method and Biochar Additives(KNUST, 2023-09) Peprah, Blissbern OwusuGhana shares similar challenges with other developing nations regarding waste management and access to clean energy. Fortunately,these two challenges are connected. A better waste management strategy would involve converting the organic waste fractions into biogas. Nevertheless, a thorough study of the physico-chemical characteristics of the feed stocks used in the anaerobic digestion process is essential to maximize the energy potential. Consequently, the first phase of this study examined the physical chemical properties of some selected feedstocks, namely, human excrement (HE), food leftovers (FLO), kitchen residues (KR), and cowdung (CD) of Ghanaian origin using APHA standards and equipment. Results of volatile-to-total solid ratios (VS/TS), 0.97±0.001, 0.89±0.001, and 0.85±0.001 for HE, FLO,KR and CD, respectively, showed that all feed stocks had high biodegradable content. though thecarbon-to-nitrogen(C/N)ratiosforFLO(22.14±0.26),KR(23.34±0.25) and CD(26.19±0.47)werewithintheoptimalrange,thatofHE(8.29±0.09)was significantly low.Withameanalkalinityof1219.67±1.53,630.00±0.58,590.00± 2.08 and15,730.00±6.00mgCaCO3 eq./L forHE,FLO,KRandCDrespectively, it wasobservedthatonlyCDhastheoptimalalkalinityvalueforanaerobicdiges- tion. Thisbroughtintoperspectivetheneedforco-digestion.Thesecondphaseof the study,therefore,soughttoprovethehypothesisthatanaerobicco-digestionofHE, FLO andKRcouldgeneratemorebiogaswhileremainingstableifpositivesynergis- tic effectsareachieved.Arandomizedternarymixturedesignandaresponsesurface approach wereusedtoascertaintherelationshipbetweensubstratemixture,biogas yield, methaneyield,andsynergy.ThefindingsrevealedthatR9(78.8%HE:11.8% FLO:9.4 %KR)hadthehighestmethaneyieldof764.79mLCH4/gVS andasyner- gistic indexof3.26.Additionally,the3Dresponsesurfaceplotsshowedimportant and sharedinteractionsbetweenHE,FLO,andKRwherebythepredictedresponses increased withincreasingHEandKRfractionsanddecreasedwithincreasingFLO fractions inthesubstratemixtures.Inthethirdphaseofthestudy,theexperimental cumulativemethaneyieldfromtheoptimumanaerobicco-digestionratio,R9,wasfit- ted tofivekineticmodelsandtheconemodelhadthebestfitrecordingan R2 value of 0.9909.Finally,theeffectsofcoconutshell(CCN)andpalmkernelshell(PKN) biochar dosages(3g,6gand10g)ontheanaerobicco-digestionofHE,FLOand KR wereinvestigatedusingbatchmesophilicexperiments.Theresultsshoweddif- ferences inthepeakoccurrencetimesandmethaneyieldswiththebiochar-amended treatments peakingearlierthanthecontroltreatment.Further,methaneyield(456.25 mLCH4/gVS) increasedwhen3gofCCNbiocharwasused,depictinga23.31%in- crease comparedtothecontrol(SM=370.03mLCH4/gVS). However,toohighCCN biochar dosagesof6gand10grestrictedmethaneproductionduetoapotentialstress on theanaerobicdigestionprocessbroughtonbytheaccumulationof H2 competitors of methanogensthatmighthaveclonedontoexcessbiocharandweakeneditsDIET benefit formethanogenesis.Furthermore,themethaneyieldwas368.69mLCH4/gVS, similar tothatofthecontrol(SM)when3gofPKNshellbiocharwasaddedtothe mixture offeedstocks.Nonetheless,methaneyieldincreasedby10.83%whenthe dosage ofPKNshellbiocharusedwasincreasedto6g.Conversely,PKN10gobserved a decreaseincumulativemethaneyield.Theobservedresultsindicatethatmicrobial activityandkineticscouldpossiblyberestrictedbyexcessivedosageofbiochar.This could beattributedtothepossibleadsorptionofvolatilefattyacids(VFAs)sincethe adsorption mechanismofbiocharisnotselective.Hence,higheramountsofadded biochar maynotnecessarilycorrespondtohigherdigestionefficiency.
- ItemLand use change, modelling of Soil Salinity and households’ decisions under Climate Change Scenarios in the Coastal Agricultural Area of Senegal(June, 2019) Thiam, Sophie; ; ;Soil salinity remains one of the most severe environmental problems in the coastal agricultural areas in Senegal. It reduces crop yields thereby endangering smallholder farmers’ livelihood. To support effective land management, especially in coastal areas where impacts of climate change have induced soil salinity and food insecurity, this study investigated the patterns and impacts of soil salinity in a coastal agricultural landscape by developing an Agent-Based Model (ABM) for Djilor District, Fatick Region, Senegal. Landsat images for 1984, 1994, 2007 and 2017 combined with normalised difference vegetation index (NDVI), elevation, wetness index and distance to the river were used to determine Land use-land cover and salinity changes. Land use classification and intensity analysis were applied to determine the time intervals during which the annual change area is relatively slow versus fast, and the variation of the categories’ gains and losses during a time interval. Soil samples plots (at 0-30 cm depth) were collected according to different land use, soil and crop types to determine the salinity patterns. Households’ survey data were collected based on 304 selected respondents to assess the perception and adaptation strategies of farmers. Land Use-Salinity Interaction (LUSI) was developed to explore the potential impacts of increased temperature and farmers’ decisions on soil salinity dynamics. Salt content, crop yield and households’ decisions sub models were incorporated in LUSI model. Three scenarios were simulated over a 20-year period, namely Baseline (current trend), 1 °C increase in temperature (Temp1) and 2 °C increase in temperature (Temp2). Eight LULC were identified in Djilor: mangrove, forests, savannah shrubs, croplands, bare lands, salt marshes, sabkha and water bodies. Forests and croplands constitute the major land use in terms of area. Croplands recorded the highest gain (17 %) throughout the period from 1984 and 2017, while forest registered the highest loss (12.5 %). The time interval 1984- 1994 had the fastest annual area change. Regarding soil salinity, bare lands, fallow lands, rice plots and Fluvisols registered high values in salt content. Clay content, elevation and distance to river were the important factors associated with the increased salt content. In 1984, highly saline and moderately saline areas were the largest in extent 32.65 % and 38.9 %, respectively. In 2017, slightly saline areas increased to 39.69 %, while highly saline and moderately saline areas decreased to 20.85 % and 25.60 %, respectively. Sabkha and salt marshes cover had the largest salt-affected areas over time. Regarding the social response to salt content, local perception of soil salinity indicates a general increase of soil salinity in the area. Women group engaged in rice farming appeared to be more affected by soil salinity. To cope with the negative impact of soil salinity, the farmers’ strategies are mainly the application of chemical fertilizer and manure, planting and conservation of trees, and installation of soil bunds. Simulation of soil salinity under current conditions showed an increasing trend of salinity over the next 20 years. The average EC was 6.48 dS/m and 9.77 dS/m for Temp1 and Temp2 scenarios, respectively for the period 2017-2036. Temp1 and Temp2 scenarios will contribute to increase the mean EC by 7.7 % and 15.8 % per year, respectively. Simulated salinity will also contribute to decrease crop yield. Rice crop registered the lowest yield over time with 228, 187, 149 kg ha-1 y-1 in BAS, Temp1 and Temp2, respectively, compared to maize, millet and groundnut. This study recommends the implementation of appropriate land management and mitigation strategies for preventing climate change and its effects on salinity dynamics in the coastal regions of Senegal by policy makers and other stakeholders.
- ItemEvaluating the effect of stone bunds erosion control on vegetation trend in South-West Burkina Faso - A fine scale remote sensing perspective in the Ioba Province(November, 2019) Asare, Yaw MensahSoil erosion by water has become a worldwide issue due to its environmental and socioeconomic impact in the light of rising concerns over climate change. To minimize the impact of soil erosion by water in West Africa, several erosion control measures have been adopted and are being practiced. The type of erosion control measure practiced depends on the climatic zone in which the area falls. In South-West Burkina Faso where this study was undertaken, rainfall is relatively high compared to the other areas within the country. As a result, the use of stone bunds/lines is the most commonly practiced erosion control measure. But after the implementation of these erosion controls, very little has been done on evaluating the impact of these erosion controls on vegetation (crops and natural vegetation) improvement using remote sensing data. This is because until recently, organized erosion control measures more especially using stone bunds over thousands of hectares of both agriculture and non-agriculture lands was rare. This study, therefore, investigated the effect of stone bunds erosion control measure on vegetation trend using remote sensing data. A time series analysis of NDVI data from 2004 to 2017 was conducted to find: (i) the trend of vegetation in the whole study area and (ii) the trend of vegetation in areas with stone bunds erosion control and areas without. Subsequently, a comparison using the ANOVA test was done between the trends of NDVI in these two areas. Also, a seasonal analysis of the crop heights of cotton and millet was conducted using photographs from UAV. Lastly, a pixel-wise trend was conducted for climate variables (rainfall and temperature) and a correlation analysis was also performed between NDVI and climate variable time series. The results showed that, the NDVI trend of the whole study area is significantly increasing at a rate of 3.7 x 10-4 ΔNDVI/month at 95% confidence interval (CI). Similarly, areas with stone bunds erosion control and areas without stone bunds erosion control had significant increasing trends ranging from 3.14 x 10-4 to 3.95 x 10-4 ΔNDVI/month and 3.83 x 10-4 to 3.91 x 10-4 ΔNDVI/month respectively. In comparing the NDVI trends of the two areas, the result from the ANOVA test showed that there is no significant difference between the NDVI trends of areas with stone bunds erosion control and areas without stone bunds erosion control (p-value = 0.319). Although, the mean NDVI trends for the whole area gave a positive trend, the results of the pixel-wise analysis showed that, positive, stable and negative NDVI trends were widespread in the study area with a range of -0.001 to a maximum of 0.002 ΔNDVI/month. Only 10.6% of the NDVI trends was statistically significant at 95% CI. In comparing the crop heights in areas with stone bunds erosion control and areas without, at 95% CI, the t-test revealed that there is no significant difference between the means of the crop heights of cotton (p-value = 0.389) and millet (p-value = 0.884) in these two areas. For trends of climate variables, rainfall and temperature had a positive increase in the monthly trend of 0.12mm/month and 0.01°C/month respectively. In terms of the correlation between NDVI and climate variables, there was a positive correlation between NDVI and rainfall (Kendall τ of 0.513), whiles a negative correlation (τ = -0.322) was observed between NDVI and temperature. The results from this study will help future studies of evaluation of erosion control measures in West Africa. By combining data from other satellites such as the Sentinel, this will go a long way to help to bridge the problem of data availability for vegetation time series analysis.