Browsing by Author "Kelbessa, Ensermu (Professer)"

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    Ecology, Carbon Stock and Formulation of Allometric Equation for Selected Tree and Shrub Species In Gerba Dima Forest, Southwestern Ethiopia
    (Addis Ababa University, 2018-06-02) Dibaba, Abyot; Soromessa, Teshome (PhD); Kelbessa, Ensermu (Professer)
    Ecology, Carbon Stock and Formulation of Allometric Equation for Selected Tree and Shrub Species in Gerba-Dima Forest, Southwestern Ethiopia Abyot Dibaba Hundie, Ph.D. Dissertation Addis Ababa University, 2018 This study was conducted in Gerba Dima Forest, South Western Ethiopia, to estimate the carbon stock, formulate allometric equations for selected tree and shrub species, determine species diversity, vegetation structure and regeneration status of woody species. A total of 90 sample plots were laid by employing stratified random sampling. Semi destructive method which involves climbing a tree was used to collect data to formulate tree allometry while destructive sampling was used to collect data for development of shrub allometric equation. A total of 180 plant species belonging to 145 genera, 69 families and comprising of 15 endemic species were recorded. Cluster analysis resulted in five different plant communities and this result was supported by the ordination result. RDA result showed altitude was the main environmental variable in determining the plant communities. Structural and regeneration status analysis of tree species revealed different population structures. The mean total carbon stock density of Gerba Dima forest was found to be 586.7 tons Carbon ha-1, out of which 243.8, 45.97, 0.03 and 292tons Carbon ha-1 were stored in the above ground, below ground, litter and as soil organic carbon, respectively. Seven allometric models were developed for 5 tree and 2 shrub species. The best-fit models were selected based on their adjusted r2, RMSE and AIC values. The study forest can play a significant role in biodiversity conservation as well as climate change mitigation since it harbors high species diversity, richness and can sink 2153 tons of Carbon dioxide. However, studies on the structure and regeneration of some woody species indicated that there are species that require urgent conservation measures. Sound management and monitoring, as well as maintenance of biodiversity, cultural and economic values of the forest require conservation activities that promote sustainable uses of the forest and its products.
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    Vegetation Ecology and Carbon Stock of Wof-Washa Forest, North Shewa Zone, Amhara Region, Ethiopia
    (Addis Ababa University, 2018-04-01) Tilahun, Abiyou; Kelbessa, Ensermu (Professer)
    Vegetation Ecology and Carbon Stock of Wof-Washa Forest, North Shewa Zone, Amhara Region, Ethiopia Abiyou Tilahun Ayalew, PhD Dissertation, Addis Ababa University, 2018 Dry Afromontane forest in Ethiopia including Wof-Washa Forest is the most altered, exploited and fragmented vegetation type. Thus, the purpose of this study is to investigate plant species diversity and structure, natural regeneration potential, carbon stock and extent of land use land cover change of Wof - Washa forest. Systematic sampling design following transect lines of 1000 meter intervals and 100 m altitudinal drop were used. Vegetation data were collected from 95, 20 x 20 m2 plots for tree species and 5, 5 x 5 m2 and 1 x 1 m2 subplots for sapling and herb species respectively. All plant species were recorded and voucher specimens were collected. Height, DBH, and cover abundance values were measured. Regeneration status of woody species was analyzed by using total count of seedling and saplings. Topographic variables such as aspect slope, altitude, and geographical coordinates were measured at each plot. Soil samples for soil seed bank analysis and carbon stock estimate were taken from 9 cm and 30 cm depth at five sub plots in each plot. Hierarchical cluster analysis was computed to identify plant community types. Shannon Wiener diversity index was used to compute the plant species richness, and evenness. Jaccard and Sorensen’s similarity coefficients were used to measure species similarities among community types and soil seed bank layers. Basal area, frequency, density and importance value index were computed. Allometric model equation was used to estimate carbon stocks. Canonical correspondence analysis (CCA) was used to analyze the relationship between plant community types and environmental variables. Three satellite images (TM - 1985, ETM+ - 2000 and OLI - 2015 were acquired for land use land cover change analysis. SPSS, R, Arc GIS, Past softwares and Microsoft Excel sheet were used for data analysis. A total of 394 plant species were identified. Asteraceae (62 species) Poaceae (30 species) and Fabaceae (29 species) were the dominant families. 46 endemic plant species to Ethiopia and 13 new records for Shewa Floristic region were identified. Five plant communities were identified and named after the first two species with high synoptic values. The result of CCA reveals that altitude, disturbance, and slope were among the main environmental variables determining plant species distribution pattern and community type formation. The density of mature woody species with DBH > 2.5 cm, > 10 and > 20 cm accounted for 1046.6 stems ha-1, 569.5 and 303.4 stem ha-1 respectively. The total basal area per hectare of woody plant species was 153.26 m2ha-1. Juniperus procera was the most frequent species (79.95 %). The highest IVI value (46.07%) was recorded for six of the most frequent woody species. The overall Shannon-wiener diversity and evenness values were 4.37 and 0.8 respectively. DBH and Height class distribution shows relatively inverted J-shape distribution. 5549 seedlings (76 plant species) were recovered from soil seed bank of Wof-Washa Forest. About 51 % and 34 % of carbon stock were contributed by the aboveground vegetation and soil respectively while the rest of the carbon pools accounted to 11.37 %. Higher carbon stock 298.9 ± 117.8 t/ha were obtained at lower altitudes followed by middle altitude 287.6 ± 192.5 t/ha. Landsat image analysis revealed a continuous expansion of agricultural land and settlement area. In addition, field survey identified that human-induced pressures especially free grazing and human encroachment are the most pressing and persistent driving forces. Therefore, owing to the high biodiversity, carbon stock and anthropogenic pressure, Wof-Washa Forest requires urgent interventions that reduce the threat levels for the maintenance of forest ecosystem services and functioning.