College of Agriculture & Environmental Sciences

EFFECT OF ENCLOSURES ON VEGETATION COMPOSITION, SPECIESDIVERSITY AND SOIL PHYSICOCHEMICAL PROPERTIES IN SEMI-ARIDRENGE LANDS OF MEYUMULUKE DISTRICTS, EAST HARARGHE, ETHIOPIA

Sat, 01 Jan 2022 00:00:00 GMT

EFFECT OF ENCLOSURES ON VEGETATION COMPOSITION, SPECIESDIVERSITY AND SOIL PHYSICOCHEMICAL PROPERTIES IN SEMI-ARIDRENGE LANDS OF MEYUMULUKE DISTRICTS, EAST HARARGHE, ETHIOPIA Ahmedjowar Mohammedamin Yusuf; Sileshi Gadissa (Ph.D.); Takele Wolkaro (Ph.D.); Kidane Gebremeskel (Ph.D.) Grazing is the most important factor af ecting vegetation and soil properties in range lands. It has a critical impact on range land biodiversity and vegetation composition. Use of enclosuresarea in many parts of semiarid range lands of the world has gained widespread acceptanceasmeans to restore degraded range land ecosystems. Therefore, this study assesses the ef ect of range land enclosures on vegetation composition and species diversity and soil physico-chemical properties in semi-arid range lands of Meyumuluke districts in East HarargheZone, Oromia Region of Ethiopia. For the vegetation and soil data collection, line transect technique was used for enclosure and communal grazing area in this study. In both enclosureand communal grazing areas a total of 36 quadrants of 20mx20m were established along12parallel line transects by 200m interval. These 20mx20m quadrants were used for woodyvegetation data collection. Within quadrants of 20mx20m again five 5m×5m(for shrub) andfive 1mx1m (for herbaceous and soil) sub-quadrants were established, four at the corners oneat the center. This forms the total of 180 (5mx5m) and 180 (1mx1m) for both enclosureandcommunal grazing areas. T-test was employed to compare mean dif erences betweenenclosures and communal grazing areas. Enclosure area enhances herbaceous speciesdiversity and reduces the woody species compared to communal grazing area. The result indicated that Shannon diversity index and species richness of woody vegetationweresignificantly (P<0.05) higher in communal grazing area, while, the Shannon diversityindexand species richness of herbaceous vegetation were significantly (P<0.05) higher in enclosurearea compared to communal grazing area. Likewise textural dif erences were also observedbetween enclosure and communal grazing area. Where the study revealed that, sandfraction was significantly (P<0.05) higher in communal grazing, while, silt fractionwassignificantly (P<0.05) higher in enclosure area. The soil chemical property suchas soil organic matter, nitrogen and soil reaction of the enclosure area were significantly (P<0.01)higher as compared to communal grazing area. In general the result of this study showed that the establishments of enclosure area in semi-arid range land has positive ef ectsonherbaceous vegetation composition that could also, improve soil properties whileit reducing the diversity of woody vegetation. 74p.

Genotype x Environment Interaction and Stability Analysis in Upland Rice (Oryza sativa L.) Varieties in Ethiopia

Thu, 01 Aug 2019 00:00:00 GMT

Genotype x Environment Interaction and Stability Analysis in Upland Rice (Oryza sativa L.) Varieties in Ethiopia Desta Abebe; Wassu Mohammed (PhD); Abush Tesfaye (PhD) In Ethiopia, rice variety development program was started recently but many rice varieties were recommended for production. However, little information is available about the yield potential of varieties over diverse environments. This research was conducted to assess the magnitude of environment (E) and genotype x environment interaction (GEI) effects on yield and yields related traits, stability of the rice varieties for yield and to evaluate and stratify rice testing environments in Ethiopia. Twenty rice varieties were evaluated at six sites during 2016/17 in randomized complete block design with three replications. The combined analysis of variance over environments showed significant differences among genotypes (G), environments (E) and significant effect of GEI on phenology, growth traits, yield components and grain yield of varieties. Analysis of variance from Additive Main Effects and Multiplicative Interaction (AMMI) model revealed that G, E and GEI contributed 3.03 to 33.58, 25.69 to 72.02, and 7.09 to 30.36 %, respectively, to the total sum squares of traits. The E and GEI had a higher contribution than G to most of the traits, and GEI had larger contribution than G and E to the variations of varieties for yield. The interaction principal component axis one (IPC1) and two (IPC2) contributed 37.94 to 88.85 and 8.92 to 87.13% to sum squares of GEI, respectively. The varieties had mean yield of 3.509 t ha-1, and 9 and 11 varieties had mean yield lower and higher than the average yield of genotypes, respectively. The stability parameters of regression coefficient (bi) and deviation from regression (S2di) from Eberhart and Russell's (ER’s), IPCA1, IPCA 2, AMMI stability value (ASV) from AMMI model, GGE biplot, Francis and Kannenberg's coefficient of variability (CV), Lin and Binns's cultivar performance measure (Pi), Shukla's stability variance (δ2i), Wricke's ecovalence (Wi), Finlay and Wilkinson's (bi), Nassar and Huehn’s mean Absolute rank difference (Si1) and variance of ranks (Si2) were used evaluate the stability of genotypes for yield. NERICA-3, Hidasse and Chewaqa varieties had 15.99, 15.7 and 15.42% higher yield than average yield of genotypes, respectively, and identify as responsive to changing environments, selected as the first four best genotypes across poor to most favorable environments and GGE biplot identified as ideal and stable varieties suggested to be used for production across environments. NERICA-12 and ADET varieties had 12.85 and 8.29% higher yield, respectively, than average yield of genotypes and identify as most stable by most of the stability parmeters and considered as wide adaptable varieties. NERICA-4, NERICA-13 and Getachew varieties had 11.97, 10.83 and 5.7% yield advantages over the average yield of genotypes, identified as stable varieties by most of the stability parameters and selected as the first four best genotypes at poor to average environments suggested to be used in these environments. The GGE biplot identified Pawe and Tepi as most discriminating environments, Manbuk and Maitsebri identified as average environments and Woreta as representative environments that could be used as test environments to develop varieties at different stages of breeding activities. The stability parameters from ER's and AMMI models had positive and significant rank correlations with most of the stability parameters and yield and considered as sufficient to evaluate the stability of genotypes for yield. In conclusion, it is suggested to conduct the experiment over seasons to certain the results due to the significant effect of GEI and its larger contribution to the variations of varieties for yield and other traits. 125

Genetic Diversity and Ecology of Lepidopteran StemBorers in Rwanda

Mon, 01 Jun 2026 00:00:00 GMT

Genetic Diversity and Ecology of Lepidopteran StemBorers in Rwanda Ntirenganya Elie This thesis examines ecology, host interactions, genetic diversity, and evolutionary patterns of Lepidopteran stemborers in the agroecological landscapes of Rwanda. It emphasizes on their impacts on cereal and sugarcane stemborers and wild species, their ecological dependence on wild host vegetation, and their responses to climate and landscape changes. Recent studies reported that stemborers have started to shift from their natural habitats and attacking new host plants that were not used to be hosts before. The research was motivated by high speed increasing landuse change by agriculture intensification and urbanization in changing climate that modify natural habitats of stemborers. In addition to this curiosity, less information on stemborer population in Rwanda is available and do not clearly show how environmental gradients, vegetation mosaics, and and these changes reshape stemborers community structure and genetic composition. The field-based ecological results revealed a substantial species richness, host-plant diversity, and habitat-driven distribution patterns. Surveys yielded 18 stemborer genera recorded from 56 host plant species. The most interesting points is that the highest abundance and diversity of stemborers were concentrated in urban and peri-urban wetlands of Kigali City, highlighting the ecological role of human-modified habitats. Poaceae hosts accounted for over 60% of all larvae collected, and common species exchangeable from wild to crop vis versa for survival, where Napier grass (Pennisetum purpureum) served as the primary refugia during dry. The specific survey conducted in sugarcane plantation shows that sugarcane support mass population of Eldana Saccharina Walker, 1865. The population vary by season and first population start in May, a month of transition between heavy rain season (March-early May) to dry late May to August. The population reached peak in August. The infestation severity varied across sugarcane varieties with the most affected was green and red sugarcane varieties that whitepowdery sugar industrial variety. Sanitation practices of old-leave removal in sugarcane plantation have shown a critical effect in reducing population dynamics of sugarcane stemborers, suggesting this practice as pesticides-free method to control stemborers in sugarcane plantation system. For molecular ecology of key stemborer species through genetic analyses of Sesamia nonagrioides (Lefèbvre, 1827) and E. saccharina, Ethiopian population as earliest studied populations in Africa xxii were used as model to understand Rwandan population’s genetic diversity and diververgence. Mitochondrial COI sequencing showed high genetic diversity in selected model species that were associated with wetland vegetations and these from maize and sugarcane. Among these species, wetland associated species and these associated with crops were standing alone as connected sisters that share common ancester but evolved differently in different time. There were no shared haplotypes between population of Rwanda and model population from Ethiopia. The results suggest that over time, landscape history, wetland degradation, climate gradients, and agricultural expansion are shaping contemporary genetic differentiation, and concludes that region-specific biological control strategies, improved surveillance, and cross-habitat management are essential, as genetically distinct populations may respond differently to control measures. Observed variations in the distribution of pest and non-pest stemborer species, together with differences in genetic structure among key model species, indicate that no single management strategy is suitable across landscapes and that continued habitat fragmentation will likely destabilize ecosystems, leading to host range expansion or local extinctions. These patterns reflect broader environmental change, where habitat fragmentation at the local scale reduces connectivity and gene flow, while climate change at regional and global scales drives shifts in species distribution, community reorganization, and biodiversity loss. Together, these processes highlight the need for multi-scale, integrative research to understand stemborers species responses to these combined effects and to support the development of context-specific, climate-smart integrated pest management strategies for sustainable agriculture. 213

Genetic Diversity and Ecology of Lepidopteran StemBorers in Rwanda

Mon, 01 Jun 2026 00:00:00 GMT

Genetic Diversity and Ecology of Lepidopteran StemBorers in Rwanda Ntirenganya Elie This thesis examines ecology, host interactions, genetic diversity, and evolutionary patterns of Lepidopteran stemborers in the agroecological landscapes of Rwanda. It emphasizes on their impacts on cereal and sugarcane stemborers and wild species, their ecological dependence on wild host vegetation, and their responses to climate and landscape changes. Recent studies reported that stemborers have started to shift from their natural habitats and attacking new host plants that were not used to be hosts before. The research was motivated by high speed increasing landuse change by agriculture intensification and urbanization in changing climate that modify natural habitats of stemborers. In addition to this curiosity, less information on stemborer population in Rwanda is available and do not clearly show how environmental gradients, vegetation mosaics, and and these changes reshape stemborers community structure and genetic composition. The field-based ecological results revealed a substantial species richness, host-plant diversity, and habitat-driven distribution patterns. Surveys yielded 18 stemborer genera recorded from 56 host plant species. The most interesting points is that the highest abundance and diversity of stemborers were concentrated in urban and peri-urban wetlands of Kigali City, highlighting the ecological role of human-modified habitats. Poaceae hosts accounted for over 60% of all larvae collected, and common species exchangeable from wild to crop vis versa for survival, where Napier grass (Pennisetum purpureum) served as the primary refugia during dry. The specific survey conducted in sugarcane plantation shows that sugarcane support mass population of Eldana Saccharina Walker, 1865. The population vary by season and first population start in May, a month of transition between heavy rain season (March-early May) to dry late May to August. The population reached peak in August. The infestation severity varied across sugarcane varieties with the most affected was green and red sugarcane varieties that whitepowdery sugar industrial variety. Sanitation practices of old-leave removal in sugarcane plantation have shown a critical effect in reducing population dynamics of sugarcane stemborers, suggesting this practice as pesticides-free method to control stemborers in sugarcane plantation system. For molecular ecology of key stemborer species through genetic analyses of Sesamia nonagrioides (Lefèbvre, 1827) and E. saccharina, Ethiopian population as earliest studied populations in Africa xxii were used as model to understand Rwandan population’s genetic diversity and diververgence. Mitochondrial COI sequencing showed high genetic diversity in selected model species that were associated with wetland vegetations and these from maize and sugarcane. Among these species, wetland associated species and these associated with crops were standing alone as connected sisters that share common ancester but evolved differently in different time. There were no shared haplotypes between population of Rwanda and model population from Ethiopia. The results suggest that over time, landscape history, wetland degradation, climate gradients, and agricultural expansion are shaping contemporary genetic differentiation, and concludes that region-specific biological control strategies, improved surveillance, and cross-habitat management are essential, as genetically distinct populations may respond differently to control measures. Observed variations in the distribution of pest and non-pest stemborer species, together with differences in genetic structure among key model species, indicate that no single management strategy is suitable across landscapes and that continued habitat fragmentation will likely destabilize ecosystems, leading to host range expansion or local extinctions. These patterns reflect broader environmental change, where habitat fragmentation at the local scale reduces connectivity and gene flow, while climate change at regional and global scales drives shifts in species distribution, community reorganization, and biodiversity loss. Together, these processes highlight the need for multi-scale, integrative research to understand stemborers species responses to thesehh combined effects and to support the development of context-specific, climate-smart integrated pest management strategies for sustainable agriculture 213