Theses and Dissertations

Evaluation of the level of adoption of native tree species in landscape restoration in Rwanda

2026-04-15T13:44:45Z

Evaluation of the level of adoption of native tree species in landscape restoration in Rwanda ABIMANA, CYUZUYO Henriette Studies indicate that forest and land degradation is a serious problem worldwide, developing countries in particular, and to reverse large-scale degradation and deforestation goes beyond what can be achieved by site-level ecological restoration. This study assessed the level of adoption of native tree species for landscape restoration in Rwanda, focusing on Rulindo District. A purposive random sampling approach was employed to interview 95 farmers using face-to-face structured questionnaires. The results highlighted that 84.21% have already planted native species while 15.79% did not. Regarding the adoption level, this study found a significant variation in the adoption of native species being used in landscape restoration. Markhamia lutea was found to be the most adopted tree species in the Rulindo (30.8%) followed by Ficus thoningii (18.6%), Erythrina abyssinica (16.2%), Mitrygnya rubrostipulata (9.6%), Polyscias fulva (9%), Afrocarpus falcatus (8.1%), Maesopsis eminii (5.1%), Tetradenia riparia (1.2%), Maesa lanceoalata (0.6%) and Sesbania sesban and Ficus ovata (0.3%). For the exotic tree species, of the most adopted species was Greveilla robusta (38.9%) followed by Alnus acuminata (17.8%), Persea americana (16.5%), Citrus x limon (13.1%), Psidium guajava (7.5%), Mangifera indica (4.4 %). Cedrela serrata (0.9%), Calliandra houstoniana var. calothyrsus (0.6%) and Citrus × aurantiifolia (0.3%). All respondents acknowledged the importance of growing native trees, with 84% rating their preference as high. Furthermore, 94% recognized ongoing community conservation efforts to conserve native trees in their respective community, 4% are not sure and 2% responded that there are no efforts in place. The adoption was facilitated by community champion groups and cooperatives (39%), the government (18%), the role played from other initiatives (14%), the intervention of NGOs (12%), incentive mechanisms (8%,) among others. Moreover, it revealed that the successes are associated with diverse benefits such as fuelwood (19%), soil enhancement (17%), and timber production, shade (13%), medicine (12%), fencing 10%), food (7%), cultural use (4%) provided by native tree species. However, despite the level of the success, challenges still persist, including limited seed availability (30%), low germination rates (27.6%), poor soil and climate conditions (18.5%), low seedling survival (12.7%), and high seedling costs (9.1%). Thus, this study recommend to increase native species coverage in Rwandan by bridging the highlighted challenges. The findings provide a good source of information to refer to for the landscape restoration using native tree species in similar ecological areas to the District of Rulindo. Master's Dissertation

Temporal and Spatial dynamics of native and exotic trees in southwestern Rwanda: case study of Nkungu and Nzahaha sectors of Rusizi district

2026-04-15T13:43:05Z

Temporal and Spatial dynamics of native and exotic trees in southwestern Rwanda: case study of Nkungu and Nzahaha sectors of Rusizi district NDIKUBWIMANA, Pascal This study assessed the spatial dynamics of native and exotic agroforestry tree species in Nkungu and Nzahaha sectors of Rusizi District, Southwestern Rwanda, an area increasingly affected by land degradation, biodiversity loss, and declining agricultural productivity. Understanding how farmers choose and distribute tree species in such vulnerable landscapes is essential for promoting sustainable agroforestry. However, empirical data on the balance between native and exotic species, their spatial arrangement, and the motivations behind species selection remain scarce in Rwanda’s southwestern highlands. To address this gap, 100 agroforestry-practicing households were selected using Cochran’s formula, as adapted by Gahutu Mbabarira and Nahayo (2020), ensuring statistical rigor with a 95% confidence level and 5% margin of error. Data were collected through structured household questionnaires, direct tree counts, and field observations to evaluate species composition, planting history, spatial patterns, and socio-economic drivers behind species preferences. The findings revealed a dominance of exotic tree species, with a native-to-exotic ratio of approximately 1:1.92. Grevillea robusta and Markhamia lutea emerged as the most commonly planted exotic and native species, respectively. Mann–Whitney U tests indicated a statistically significant difference in planting frequency between these categories (p < 0.001). Exotic species were often planted near homesteads and accessible zones, while native species were dispersed across marginal and less-managed areas. Farmers’ tree selection was heavily influenced by institutional support (68%), economic profitability, and seedling availability. While native species were valued for their ecological functions, market pressures and limited propagation resources reinforced the preference for exotics. The study was conducted to fill a critical information gap regarding the ecological and socio-economic dimensions of tree species selection in agroforestry. By generating localized evidence on species use, distribution, and farmer preferences, the research provides practical guidance for policymakers, extension services, and restoration programs seeking to align agroforestry interventions with both productivity goals and biodiversity conservation in Rwanda and similar landscapes. Master's Dissertation

An investigation into the quality performance of road projects in Kigali, Rwanda

2026-04-15T13:36:28Z

An investigation into the quality performance of road projects in Kigali, Rwanda UWINTWALI, Jean de Montfort This study “an investigation into the quality performance of road projects in Kigali, Rwanda” focused on determining the factors influencing road quality, examining critical criteria for road quality performance measurement, and recommending effective strategies for improving road project quality. A mixed-methods approach was employed, combining quantitative data from structured questionnaires with qualitative insights from field observations, interviews, and document reviews. The study involved 94 respondents, including engineers, contractors, consultants, project managers, and road users, and covered four strategically selected road projects across Kigali’s districts. Regarding findings the study has revealed that there was a strong consensus among Project Managers, Road Engineers/Contractors/Consultants, and Government officials in Kigali regarding both the factors influencing road quality performance and the critical criteria for its measurement, as well as effective improvement strategies. Across all project phases (initiation, procurement, execution, monitoring, closure), factors such as project design quality, contractor qualification and experience, skilled labor, compliance with specifications, and regulatory enforcement were consistently rated as highly influential. Similarly, road geometry, pavement integrity, drainage, and smoothness were universally prioritized as key measurement criteria. For improvement strategies, use qualified and skilled contractors, comply with design specifications and standards, use certified materials, and strengthen project planning and design were top-ranked. Crucially, ANOVA results consistently showed no statistically significant differences in perception among the professional groups for nearly all factors, criteria, and strategies (all p-values ≥ 0.05). This indicates a remarkable, shared understanding and alignment among stakeholders on road quality aspects in Kigali, providing a solid foundation for collaborative initiatives. Minor, nonsignificant variations in mean scores suggest subtle differences in emphasis, but overall agreement is high. Master's Dissertation

Assessing the impact of lightning strike disturbances on vegetation regeneration in Nyungwe National Park's Tropical Forest Ecosystem

2026-04-15T13:33:57Z

Assessing the impact of lightning strike disturbances on vegetation regeneration in Nyungwe National Park's Tropical Forest Ecosystem MANIRIHO, Jean d'Amour Lightning is an often-overlooked yet powerful disturbance shaping tropical forest dynamics. In Nyungwe National Park, Rwanda, where thunderstorms occur on over 220 days annually, lightning is likely to play a critical role in vegetation regeneration and forest structure. This study investigated the ecological impacts of lightning strikes by comparing three disturbance regimes: lightning-damaged patches, non-lightning disturbed patches (caused by landslides, erosion, and other factors), and undisturbed forest controls. A total of 62 plots were surveyed to assess tree, shrubs and seedling density, species composition, and structural attributes such as diameter at breast height, height, canopy cover, crown formation, and leaf loss indices. Microclimate variables (temperature, humidity, rainfall, elevation) were measured alongside remote sensing analyses of vegetation greenness (NDVI). Results revealed that lightning strikes significantly reduced species diversity and community evenness by promoting dense regeneration dominated by a few light-demanding pioneer species, while suppressing shade-tolerant species. In contrast, non-lightning disturbed sites supported higher species richness but exhibited stunted structural development due to chronic abiotic stress. Undisturbed sites maintained the highest canopy cover, cooler temperatures, and more humid microclimates, favoring late-successional species. NDVI time-series analysis showed sharp declines in vegetation greenness immediately following lightning strikes, followed by gradual recovery in subsequent years. These findings demonstrate that lightning functions as an agent of ecological simplification, resetting successional trajectories and altering microclimates within canopy gaps. As climate change is projected to increase lightning frequency, these disturbances may become more significant for montane forest resilience and biodiversity conservation. Integrating lightning ecology into park management strategies is therefore essential for sustaining Nyungwe’s unique forest mosaic and guiding adaptive restoration efforts. Master's Dissertation