Browsing by Author "Mganga, Nyatwere D."
Now showing 1 - 8 of 8
Results Per Page
Sort Options
Item Above-Ground Carbon Allometric Models for Diplorhynchus condylocarpon (Müll. Arg.) Pichon., A Common Miombo Woodland Associate(2015-07) Mganga, Nyatwere D.; Lyaruu, Herbert V.M.; Banyikwa, Feetham F.Estimation of carbon using allometric models facilitates sustainable management of forests and woodlands. Reliable estimations of carbon in most ecosystems can only be accomplished by using species-specific allometric models which are lacking for many species. The present study was carried out so as to develop the best fit above-ground carbon allometric models of various tree components; stems, branches, twigs and leaves of Diplorhynchus condylocarpon (Horn-pod tree), a species that is commonly associated with Miombo woodlands. Twenty one trees of D. condylocarpon with a ranging diameter at breast height (DBH) from 5 to 19 cm were destructively sampled from Miombo woodlands of Kitwe in Tanzania. Linear models were assessed for above-ground carbon using regression analysis. Regression analysis was carried out by relating above-ground carbon of tree components to DBH and height (H), using DBH and H as predictor variables. The best fit allometric models for above-ground carbon of total, stems, branches and twigs and/or leaves had coefficient of determination values (R2) of 0.98, 0.98, 0.96 and 0.79 respectively at P < 0.05. Above-ground carbon allometric models developed have wide application in sustainable use of the species and carbon accounting particularly in Central Zambezian Miombo woodlands without future destructive sampling.Item Above-ground carbon stock in a forest subjected to decadal frequent fires in western Tanzania(International Network for Natural Sciences, 2017-02-14) Mganga, Nyatwere D.; Lyaruu, Herbert V.; Banyikwa, Feetham F.Gradual increase in atmospheric temperature due to elevated levels of greenhouse gases has become a global agenda. Of these gases, carbon dioxide is the most predominant accounting for more than half of the atmospheric warming. Conveniently, forests and woodlands are important sinks of carbon through sequestration which involves carbon dioxide capture and storage. Miombo woodlands are the most widespread savanna vegetation in the Sub-Saharan Africa, and like other vegetation they are likely to have a marked degree of carbon sequestration. However, these ecosystems are normally threatened by many disturbances, including outbreaks of uncontrolled and destructive fires. Yet, it has been reported that wildfires have both positive and negative influence on carbon sequestration in forests and woodlands. The aim of the present study was to determine tree carbon in Ilunde forest after consecutive exposure to frequent fires for 10 years. A fire suppressed forest of Kitwe was used as a control. Fire frequency of Ilunde forest was obtained from published Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery from the year 2001 to 2012. Tree carbon stock was estimated using biomass allometric models so far developed for miombo woodlands.The level of difference in carbon density between the two forests was determined using t-test. Tree carbon stock was significantly high in Kitwe forest than in Ilunde (P < 0.05). The effects of wildfires are variable depending on the nature of ecosystems and the existing circumstances. Since fire is crucial in miombo woodlands, then prescribed burning could be prioritized to sustain sinks of carbon.Item Applicability of Satellite Remote Sensing in Accounting Above-Ground Carbon in Miombo Woodlands(2015-10) Mganga, Nyatwere D.; Lyaruu, Herbert V.M.The crisis of climate change has drawn attention of ecologists all over the world to explore ways that could effectively enhance the sequestration of carbon in forests and woodlands. This necessitates forest inventory, along with knowledge of techniques that are quick and manageable. The present study was carried out in Miombo woodlands of western Tanzania namely, Kitwe and Mgaraganza. The aim of the present study was to investigate the effectiveness of remote sensing in estimating the stock of carbon in Miombo woodlands. Two types of data namely, ground-truthing and satellite imagery were used. Ground-truthing data were obtained by measuring the diameter at breast height (DBH) of all trees in 30 and 20 concentric plots in Kitwe and Mgaraganza forests, respectively. The average DBH of trees in each forest was fitted in biomass allometric models to estimate the ground-truthing vegetation biomass. On the other hand, Landsat images of the two forests were used to compute the Normalised Vegetation Index (NDVI). The computed NDVI were regressed with the ground-truthing vegetation biomass to get the remotely sensed vegetation biomass which was assumed to be 50% carbon. The coefficients of determination between the ground-truthing above-ground biomass and the NDVI values were statistically significant at P<0.05. The above-ground carbon stock obtained by ground-truthing in Mgaraganza and Kitwe forests was 3 and 2 times higher than that of satellite remotely sensed data respectively. The above-ground carbon stock obtained from satellite remote sensing gives some impression thus a basis for remote sensing in Miombo woodlandsItem The Density of Carbon in Miombo Woodlands Subjected to Different Fire Frequency(2015-09) Mganga, Nyatwere D.African miombo woodlands are concentrated in the Sub-Saharan region. The United Nations Framework Convention on Climate Change (UNFCCC) under the Kyoto Protocol recognizes the role of carbon sequestration in forests and woodlands. Due to large area coverage and inaccessibility, African savanna fires are normally left unattended hence resulting in outbreaks of uncontrolled and destructive fires commonly called wildfires. It has been reported that wildfires have both negative and positive influence on carbon sequestration in forests and woodlands. The present study was conducted in three forests namely Kitwe, Mgaraganza and Ilunde in western Tanzania. Tree carbon density was estimated using biomass allometric model so far developed for miombo woodlands and the level of significance between the differences of carbon density was determined using ANOVA. Fire frequency of the three forests was interptreted from MODIS (Moderate Resolution Imaging Spectroradiometer) satellite imagery from the year 2001 to 2012. Tree carbon stock was significantly different among the studied miombo woodlands (P < 0.05). Furthermore, it was revealed that tree carbon stock was not significantly different between Mgaraganza and Ilunde forests (P > 0.05). In Ilunde forest, the average number of wildfires per annum was 35, while in Mgaraganza and Kitwe forests were 0.4 and 0.08, respectively. The effects of wildfires are variable and contradictory depending on the nature of the ecosystems and the existing circumstances. Frequent wildfires and spontaneous suppression resulted in different carbon density. Since fire is crucial in miombo woodlands, then prescribed burning could be prioritized to sustain sinks of carbon.Item Investigation of the Desirable Predictor Variable in Accounting Above-Ground Carbon for Pseudolachnostylis maprouneifolia Pax. (Kudu-Berry)(2016-01) Mganga, Nyatwere D.Biological interactions that involve the capture of the ever increasing levels of carbon dioxide in forest ecosystems have drawn global attentions to carbon accounting. In the present study the desirable predictor variable in carbon accounting was established in Pseudolachnostylis maprouneifolia Pax. Twenty one trees of P. maprouneifolia Pax with diameter at breast height (DBH) from 5.7 to 14.7 cm and total height (H) between 300 cm to 672 cm were destructively sampled from Miombo woodland of Ilunde in Tanzania. Regression analysis was carried out by using DBH and H as predictor variables. The best fit allometric models in stems and branches were obtained when both H and DBH were used as predictor variables with coefficient of determination values (R2) of 0.99 and 0.79 at P < 0.05, on the contrary, in leaves and/or twigs the best fit allometric model had R2 of 0.96 when DBH was the only predictor variable.In P. maprouneifolia Pax. measurement of both DBH and H is recommended for reliable carbon inventory in the Central Zambezian Miombo woodlands under the specified tree dimensions.Item The Potential of Bioaccumulation and Translocation of Heavy Metals in Plant Species Growing around the Tailing Dam in Tanzania(2014-10) Mganga, Nyatwere D.The present paper covers the probability of heavy metals bioaccumulation and translocation in twelve plant species growing around the tailing dam of North Mara gold mine. In the present study about 5 g of root and shoot portions of the randomly selected plant species that were growing around the tailing dam were separately collected. Besides, 10 g of soil samples were also collected from the rhizosphere at each sampling point where vegetations were previously sampled. The soils and vegetations were analyzed for four heavy metals (lead, zinc, cadmium and nickel) by Atomic Absorption Spectrophotometer. Bioaccumulation potential was measured in the plant species by calculating Bioaccumulation Factor (BAF). BAF was obtained from the ratio of metal content in plant roots to that of total metal content in the soil. Besides, translocation potential was determined by calculation of Translocation Factor (TF), which was obtained from the ratio of the metal content in the plant shoots to that in the plant roots. Of the studied plants, only Gomphrena celosioides L., Hibiscus nicranthus L., Indigofera cuneata Bak., Acacia albida Bentha. and Cynodon dactylon (L.) Pers. had BAF and TF > 1, suggesting their applicability in extraction of the studied heavy metal-polluted soils at the study area. Since heavy metal accumulation and subsequent translocation depends on climatic and edaphic factors, more local plants which are capable of accumulating heavy metals need to be identified and tested in situ.Item Spatio-temporal scorched land and resultant sequestered soil organic carbon in selected miombo woodlands of western Tanzania(2014-10) Mganga, Nyatwere D.; Lyaruu, Herbert V.; Banyikwa, Feetham F.Ecological impacts of soil degradation in forests have been variably reported. The present study aimed at exploring the consequence of fire extent on the sequestration of soil organic carbon. Data for scorched land was captured by Landsat in Kitwe and Ilunde forests with different levels of fire extent in western Tanzania. Both forests were severely disturbed previously. Soil samples were collected from thirty plots located 150 m and 100 m apart in Ilunde and Kitwe forests respectively, for determination of soil bulky density and percentage organic carbon. In each plot soil samples were collected from four points, thereafter treated differently depending on the purpose of sampling. Percentage organic carbon was obtained using Walkley-Black method, and then the sequestered soil organic carbon was estimated in tonnes per hectare as a product of percentage organic carbon, soil depth and bulky density. The difference in sequestered soil organic carbon between the two forests was analyzed using t-test. Spatio-temporal scorched and vegetated land lands of the forests were produced from satellite images after computing Normalized Difference Vegetation Index (NDVI) for the years 1990, 2000 and 2011. In 30 cm soil depth, more soil organic carbon of 17.9 ± 0.9 t ha- (two folds) was recorded from Kitwe than Ilunde forests (P < 0.01, t = 9.935, D.F. = 29). In Ilunde forest, the extent of fire increased with time, while scorched and vegetated lands increased and decreased with time respectively. In Kitwe forest, the trend was opposite whereby the scorched land decreased and vegetated land increased with time. Prevalence of wildfires over large areas in forests lowers soil organic carbon sequestration. The contribution of ash in enrichment of soil organic carbon sequestration in forests could be only overstated.Item Variations in floristic diversity with distance around North Mara gold mine in Tanzania(2012-05) Mganga, Nyatwere D.; Manoko, Mkabwa L.K.M.; Rulangaranga, Zachariah K.Plant-heavy metal interactions and resultant variations in plant diversity are widely documented. However, such information was scanty at the study area. Three parallel line transects, each of 3500 m, 100 m apart were established opposite the mine wastes. Data were collected at Kwinyunyi (within 1 km from mine wastes) and at Masangora (within 3 km from mine wastes). Abundance of plant species was systematically recorded using nested quadrats; also, soils were sampled at each point. Soils were analyzed for bioavailable heavy metals by Atomic Absorption Spectrophotometer and for pH. The highest diversity index, richness and evenness were recorded within 1 km from mine wastes, while, the lowest diversity index and richness of plant species were recorded within 3 km from the waste. The lowest evenness of plant species was recorded within 1 km from mine wastes. T-test showed that the diversity, richness and evenness of plant species were not significantly different between Kwinyunyi and Masangora (p > 0.05). The levels of bioavailable chromium, cadmium, lead and nickel were above the internationally permissible ones. This study probably confirms that the ecosystem is robust and resilient in that plant communities sometimes adapt to conditions despite of alarmingly high levels of heavy metals.