Browsing by Author "Lyaruu, Herbert V."

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    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.
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    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.