NRU :: Browsing by Author "Agaba, Hillary"

Browsing by Author "Agaba, Hillary"

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Amending Soils with Hydrogels Increases the Biomass of Nine Tree Species under Non-water Stress Conditions
(Clean–Soil, Air, Water, 2009) Orikiriza, Lawrence J. B.; Agaba, Hillary; Tweheyo, Mnason; Eilu, Gerald; Kabasa, John David; Huttermann, Aloys
The classical aim of the application of super absorbent polyacrylate (SAPs) hydrogels is the prolonging of plant survival under water stress. Their effect on plant growth during non-water stress conditions is not known. This study examined the root and shoot biomass of seedlings of nine tree species; Eucalyptus grandis, Eucalyptus citriodora, Pinus caribaea, Araucaria cunninghamii, Melia volkensii, Grevillea robusta, Azadirachta indica, Maesopsis eminii and Terminalia superba. The seedlings were potted in five soil types; sand, sandy loam, loam, silt loam and clay. These were amended at two hydrogel levels: 0.2 and 0.4% w/w and grown under controlled conditions in a green house. Root and shoot growth responses of the seedlings were determined by measuring the dry weight of the roots, stems, leaves and twigs. The addition of either 0.2 or 0.4% hydrogel to the five soil types resulted in a significant increase of the root dry weight (p a 0.001) in eight tree species compared to the controls after 8 wk of routine watering. Also, the dry weight of stems and leaves and twigs were significantly (p a 0.001) higher in the nine tree species potted in hydrogel amended soil types than in the hydrogel free controls. These results suggested that hydrogel amendment enhances the efficiency of water uptake and utilization of photosynthates of plants grown in soils which have water contents close to field capacity.
The Economics Of The Carbon Sequestration Potential Of Plantation Forestry In South-Western Uganda
(a Journal of Forest Science, 2016) Kiyingi, Isaac; Edriss, Abdi-Khalil; Phiri, Alexander MR; Mukadasi, Buyinza; Tumwebaze, Susan; Agaba, Hillary
This study assessed the amount of carbon stored and the economic viability of the small-scale Clean Development Mechanism (CDM) carbon offsets in Pinus caribaea and Eucalyptus grandis plantations under varying rotations. Volume equations were used to estimate carbon stocks and merchantable wood volume in the plantations, while net present value (NPV) and annual equivalent value (AEV) were used as measures of profitability at the optimum economic rotation age as well as at the CDM-defined crediting period of 20 years. The findings show that over a 20-year rotation, E. grandis and P. caribaea plantations sequestered 638 and 418 t CO2-e ha−1, respectively. The NPVs of E. grandis and P. caribaea with carbon credits over the CDM carbon-crediting period of 20 years were US$2 540 ha−1 and US$1 814 ha−1, respectively. This is higher than the NPVs without carbon credits of US$1 543 ha−1 and US$1 390 ha−1 for E. grandis and P. caribaea, respectively. The AEV of E. grandis harvested at its optimal economic rotation of 10 years was US$316 ha−1. This is slightly higher than the AEV of US$298 ha−1, utilising the CDM carbon-crediting period of 20 years. In contrast, the AEV of P. caribaea under the 20-year CDM carbon-crediting period was higher than harvesting at the optimal economic rotation of 16 years without carbon credits. When the average CDM contract establishment costs exceed US$500 ha−1 and US$1 000 ha−1 for P. caribaea and E. grandis woodlots, respectively, it is not economically viable for one to participate in the CDM forest carbon offsets programme. In conclusion, the study results indicate that whereas E. grandis has a higher biological potential to sequester carbon than P. caribaea, it is currently not economically viable for participation in the CDM forest carbon offset scheme. In contrast, it is economically viable for P. caribaea plantations to participate in the CDM, if the CDM contract establishment costs are low.
Effects of Hydrogel Amendment to Different Soils on Plant Available Water and Survival of Trees under Drought Conditions
(Clean–Soil, Air, Water, 2010) Agaba, Hillary; Baguma Orikiriza, Lawrence Justus; Osoto Esegu, John Francis; Obua, Joseph; Kabasa, John David; Huttermann, Aloys
The effect of super absorbent polyacrylate (SAP) hydrogel amendment to different soil types on plant available water (PAW), evapotranspiration and survival of Eucalyptus grandis, Eucalyptus citriodora, Pinus caribaea, Araucaria cunninghamii, Melia volkensii, Grevillea robusta, Azadirachta indica, Maesopsis eminii and Terminalia superba was investigated. The seedlings were potted in 3 kg size polythene bags filled with sand, loam, silt loam, sandy loam and clay soils, amended at 0 (control), 0.2 and 0.4% w/w hydrogel. The tree seedlings were allowed to grow normally with routine uniform watering in a glass house set up for a period of eight weeks, after which they were subjected to drought conditions by not watering any further. The 0.4% hydrogel amendment significantly (p a 0.05) increased the PAW by a factor of about three in sand, two fold in silt loam and one fold in sandy loam, loam and clay soils compared to the control. Similarly, the addition of either 0.2 or 0.4% hydrogel to the five soil types resulted in prolonged tree survival compared to the controls. Araucaria cunninghammi survived longest at 153 days, while Maesopsis eminii survived least (95 days) in sand amended at 0.4% after subjection to desiccation. Evapotranspiration was reduced in eight of the nine tree species grown in sandy loam, loam, silt loam and clay soils amended at 0.4% hydrogel. It is probable that soil amendment with SAP decreased the hydraulic soil conductivity that might reduce plant transpiration and soil evaporation.
Leaf sponge tool use by Buraiga chimpanzees, Pan troglodytes schweinfurthii, in Kibale National Park, Uganda
(African Journal of Ecology, 2023) Edwards, Wren I.; Guma, Nelson; Agaba, Hillary; Balyesiima, Godfrey; Asalu, Edward; Rothman, Jessica; Stevens, Nancy J.
Chimpanzees (Pan troglodytes) are avid tool users, although tool uses and functions vary among communities. Some chimpanzees use stones or wood in extractive forag- ing to crack open nuts, whereas others use long stems to consume termites or ants. Leaf sponges are versatile and widespread tools used by chimpanzees, created by crumpling leaves in the mouth and then using the hands to immerse the tool to pro- cure liquids from difficult-to-access locations. Here we describe leaf sponge use by two female chimpanzees in Kibale National Park, Uganda, documenting for the first time tool use in the Buraiga chimpanzee community.
Nutritional prospects of jackfruit and its potential for improving dietary diversity in Uganda
(BMC research notes, 2022) Nantongo, Judith S.; Odoi, Juventine B.; Agaba, Hillary; Gwali, Samson
A sustainable way of providing essential nutrients from crops for the poor and undernourished is biofortification, through plant breeding. This study characterised the intraspecific variation of selected nutritional elements in the flakes and seeds of Ugandan jackfruit (Artocarpus heterophyllus) plus the phytochemical composition of leaves. The overall aim was to explore possibilities of selecting for varieties that are higher in selected essential nutrients. Selecting for nutrient dense crops has been mostly done for annual agricultural crops, and rarely for perennial fruit trees. Results: Uganda’s Jackfruit has high macronutrients, especially magnesium and calcium. This study revealed that the amounts of these macronutrients were higher than those found in commonly consumed fruits, giving jackfruit a nutritional advantage with respect to these nutrients. The varieties sampled also differed significantly (p < 0.01) for some nutrients such as vitamin C, crude fat, crude fibre, total soluble solids and juice yield, highlighting the potential for selection for targeted nutritional gains. The seeds however, had less amounts of most of the quantified nutrients that also differed among the varieties. Significant intraspecific variation of the leaf total phenolics was also observed. With regard to the quantified nutritional elements in the flakes, the ethno-varieties were separated in space along PC1 (p < 0.001), PC2 (p < 0.001) and PC3 (p < 0.01) indicating their distinctness.
SilicoDArT and SNP markers for genetic diversity and population structure analysis of Trema orientalis; a fodder species
(Plos one, 2022) Ssali Nantongo, Judith; Odoi, Juventine Boaz; Agaba, Hillary; Gwali, Samson
Establishing the genetic diversity and population structure of a species can guide the selection of appropriate conservation and sustainable utilization strategies. Next-generation sequencing (NGS) approaches are increasingly being used to generate multi-locus data for genetic structure determination. This study presents the genetic structure of a fodder species -Trema orientalis based on two genome-wide high-throughput diversity array technology (DArT) markers; silicoDArT and single nucleotide polymorphisms (SNPs). Genotyping of 119 individuals generated 40,650 silicoDArT and 4767 SNP markers. Both marker types had a high average scoring reproducibility (>99%). Genetic relationships explored by principal coordinates analysis (PCoA) showed that the first principal coordinate axis explained most of the variation in both the SilicoDArT (34.2%) and SNP (89.6%) marker data. The average polymorphic information content did not highly differ between silicoDArT (0.22) and SNPs (0.17) suggesting minimal differences in informativeness in the two groups of markers. The, mean observed (Ho) and expected (He) heterozygosity were low and differed between the silicoDArT and SNPs respectively, estimated at Ho = 0.08 and He = 0.05 for silicoDArT and Ho = 0.23 and He = 0.19 for SNPs. The population of T. orientalis was moderately differentiated (FST = 0.20–0.53) and formed 2 distinct clusters based on maximum likelihood and principal coordinates analysis. Analysis of molecular variance revealed that clusters contributed more to the variation (46.3–60.8%) than individuals (32.9–31.2%). Overall, the results suggest a high relatedness of the individuals sampled and a threatened genetic potential of T. orientalis in the wild. Therefore, genetic management activities such as ex-situ germplasm management are required for the sustainability of the species. Ex-situ conservation efforts should involve core collection of individuals from different populations to capture efficient diversity. This study demonstrates the importance of silicoDArT and SNP makers in population structure and genetic diversity analysis of Trema orientalis, useful for future genome wide studies in the species.
Tree species diversity and abundance in coffee farms adjacent to areas of different disturbance histories in Mabira forest system, central Uganda
(International Journal of Biodiversity Science, Ecosystem Services & Management, 2015) Gwali, Samson; Agaba, Hillary; Balitta, Paul; Hafashimana, David; Nkandu, Joseph; Kuria, Anne; Pinard, Fabrice; Sinclair, Fergus
Coffee production in Uganda is done on small-scale farms containing a very significant tree component. However, there is little information on how tree species abundance, richness and diversity change in coffee farms as distance from forest changes. The main objectives of this study, therefore, were to assess (a) abundance and (b) diversity of tree species in the coffee production systems in proximity to disturbed and undisturbed forest around Mabira forest, one of Uganda’s Robusta coffee-growing areas. Seventy-nine 0.1 ha plots were established in nine villages close to undisturbed and disturbed forest, and over 5 km from the forest. A total of 875 trees belonging to 63 species were recorded. There was significant similarity in species composition among the three study sites (analysis of similarity R = 0.09, p < 0.01; analysis of variance: F3,12 = 0.353, p = 0.79). Non-metric dimensional scaling supported these findings (stress value = 0.224 at k = 2) and showed that tree species composition in the three proximity categories was very similar. These results demonstrate that tree species composition and diversity is similar in coffee farms regardless of their distance from the nearest natural forest and forest exploitation history.
Variation in seed and seedling traits of the different ethno-varieties of jackfruit, a potential fruit tree species for food security
(Trees, Forests and People, 2022) Ssali Nantongo, Judith; Mudondo, Scovia; Oluk, Richard; Agaba, Hillary; Gwali, Samson
A key component of the performance of plant seeds is the germination capability as well as seedling survival and vigor. Seed traits from five jackfruit ethno-varieties (infra-specific diversity as understood and managed by farmers) were assessed. A greenhouse experiment was conducted to determine the survival of seeds, emergence and germination rate. Seeds from different ethno-varieties differed in their length (F (4,145) = 6.31, p < 0.001). The difference was highest between seeds from white, orange or yellow ethno-varieties. The width also slightly differed among ethno-varieties (F (4,145) = 3.29, p < 0.05). The average fresh and dry weights tended to be higher in seeds from the soft ethno-variety than the rest of the ethno-varieties. Differences in the survival of seeds and germination rate were also exhibited among ethno-varieties, where the white ethno-variety showed the highest pre-emergence mortality but at the same time the least germination time. Over the six-week period of germination, the soft ethno-variety exhibited the highest root:shoot ratio but also grew faster than all other ethno-varieties. There is potential evidence of phylogenetic constraints on seed size, germination and seedling vigor. Optimum growth for most of the traits was achieved between 6 and 7 weeks after sowing, which can guide on the time seedlings should be left in the pots before being transferred to the field. Further progeny tests should be undertaken on these provenances in the field over a longer period so as to obtain better distinction of the growth traits among the ethno-varieties.

Browsing by Author "Agaba, Hillary"

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