Browsing by Author "Tumwebaze, Susan"

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    Allometric relationships and carbon content for biomass-carbon estimation of East African Highland Bananas (Musa spp. AAA-EAHB) cv. Kibuzi, Nakitembe, Enyeru and Nakinyika
    (African Journal of Agricultural Research, 2018) Kamusingize, Daphine; Mwanjalolo Majaliwa, Jackson; Komutunga, Everline; Tumwebaze, Susan; Nowakunda, Kephas; Namanya, Priver; Kubiriba, Jerome
    Globally, interests to increase carbon stocks have gained momentum in both woody and non-woody ecosystems. Despite efforts made to generate appropriate methods to estimate these stocks, most equations developed do not cater for intraspecific variabilities across e.g. species, regions or growth stages; especially in the case of bananas. Therefore, there is need to develop more robust equations to improve on the precision of biomass-carbon prediction especially at local scales to facilitate estimation of specific carbon stocks often lost in global assessments. This study aimed at developing cultivarspecific biomass estimation relationships and determining carbon content of EAHB cultivars at two growth stages. Plant data were collected purposively using destructive sampling techniques on farmers’ plots for 4 cultivars (Kibuzi, Nakitembe, Enyeru and Nakinyika) in two agro-ecological zones: the L. Victoria crescent and the South-western farmlands in the districts of Lwengo and Mbarara respectively. Results show that biomass differed across cultivars (P<0.001); hence four equations (Enyeru, Nakinyika, Kibuzi_Nakitembe and Generic) were developed following an exponential function, y=Aexp(ax), using diameter at breast height (DBH) as the predictor variable with an R2 range of 82-94%. EAHB mean carbon content varied significantly with growth stage (P<0.05) (47.6% for maiden plants before flowering and 48.8% for mature plants with a developed bunch). This study concludes that it is important to develop cultivar-specific equations for biomass-carbon estimation of EAHB cultivars to help assess their contribution to the carbon cycle especially in future studies.
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    Carbon sequestration potential of East African Highland Banana cultivars (Musa spp. AAA-EAHB) cv. Kibuzi, Nakitembe, Enyeru and Nakinyika in Uganda
    (Journal of Soil Science and Environmental Management, 2017) Kamusingize, Daphine; Mwanjalolo Majaliwa, Jackson; Komutunga, Everline; Tumwebaze, Susan; Nowakunda, Kephas; Namanya, Priver; Kubiriba, Jerome
    Despite the global interest to increase the world's carbon stocks, most carbon sequestration strategies have largely depended on woody ecosystems whose production is threatened by the continuous shortage of land, hence the need to explore viable alternatives. The potential of bananas to sequester carbon has been reported but there is limited knowledge on the performance of various cultivars as specific carbon stocks are often lost in global assessments. Therefore, this study aimed at exploring the potential of and variability in carbon stocks of selected East African Highland Banana (EAHB) cultivars. Plant and soil data were collected using destructive and non-destructive techniques in 30×30m2 sampling plots for 4 cultivars Kibuzi, Nakitembe, Enyeru and Nakinyika growing in two agroecological zones of Uganda being the L.Victoria Crescent and the South-western region. Total carbon and Soil Organic Carbon (SOC) stocks did not differ considerably across cultivars (P>0.05). However, there was significant variation (P<0.05) in plant carbon stock being lowest in two cultivars: Nakinyika at 0.37±0.19 Mgha-1 and Nakitembe at 0.40±0.19Mgha-1; and highest in Enyeru at 1.64±0.18 Mgha-1. The SOC stock variation difference across depth was 2.9-8.5 Mgha-1 being higher in top soil than sub-soil. Despite the small plant carbon stock amounts, the system enables much more carbon to be stored in the soil considering the proportion of what is contained in the plant to that in the soil across all cultivars (0.4-2%). The study therefore recommends revision of existing carbon frameworks to incorporate the contribution of non-woody perennials like bananas in the carbon cycle so that the poor small scale farmers who cannot afford large acreages to establish tree plantations can also benefit from such initiatives.
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    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.
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    Pathogenicity of Teratosphaeria species on Eucalyptus grandis and selected hybrids in Uganda
    (Journal of Forest Research, 2021) Syofuna, Agatha; Nakabonge, Grace; Namayengo, Sarah; Tumwebaze, Susan; Banana, Abwoli
    Teratosphaeria stem canker is one of the most important diseases to have emerged on non-native plantation-grown Eucalyptus trees cultivated globally. The study assessed the pathogenicity of two Teratosphaeria species associated with Teratosphaeria stem canker and the susceptibility of Eucalyptus grandis and six commonly grown Eucalyptus hybrids to these fungal species in Uganda. The inoculation trials indicated that Eucalyptus species and hybrids were susceptible to fungal pathogens used. A comparison of Eucalyptus species and hybrids for each fungal species showed that GC 540 and GC 796/2 are the most susceptible hybrids to T. zuluensis and T. gauchensis respectively while hybrid clone GU 8 had a higher tolerance to both fungal species. GC 540 was also tolerant to T. gauchensis while F2 and GC 550 were tolerant to T. zuluensis. Eucalyptus grandis sourced from Australia (F2) showed a higher tolerance than Eucalyptus grandis from South Africa (F1). The results further revealed that both Teratosphaeria zuluensis and Teratosphaeria gauchensis are pathogenic to Eucalyptus species and hybrids. The generated information indicates that there is an opportunity to sustainably manage Teratosphaeria stem canker disease if tolerant species are grown in areas with high disease impact.