Browsing by Author "Frederk, Godfrey"

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    The effects of grazing on plant species diversity and physico-chemical characteristics of soil and water in the Kilombero flood plain, Tanzania
    (University of Dar es Salaam, 2013) Frederk, Godfrey
    A study was carried out to determine the impacts of grazing on plant species diversity and physico-chemical properties of soil and water in the Kilombero Ramsar site, a biodiversity hot spot in central Tanzania. Random systematic sampling approach was used to sample plant species, soil and water in the study sites. The soil and water PO43-, NH4+ and NO3- concentrations were determined by colorimetric method while probes were used to determine water EC in situ and pH. ANOVA showed significant difference in soil compaction among study sites (P = 0.0001), whereby soil BD was higher at the grazed Lungongole (64.3 ± 2.1 kPa) and Kiberege (27.36 ± 7.85 kPa) sites compared to ungrazed Kikandekande (3.82 ± 0.09 kPa) (P < 0.001). The grazed sites were dominated by grazing tolerant plant species like Azolla nilotica, Ageratum conyzoides, Phragmites mauritianus and Cynodon dactylon. In the ungrazed site, dominant plant species were tree stands namely Erythrophleum suaveolens, Memecylon sansibaricum and Voacanga africana to list a few. Plant species diversity was within the recommended range of tropical ecosystems of 1.5 to 3.5, in the Kilombero Ramsar site. In the dry season when grazing was heavy plant species diversity at Lungongole Kiberege and Kikandekande was 2.65 ± 0.003, 3.475 ± 0.002 and 3.583 ± 0.003, respectively. The heavily grazed Lungongole site had significantly lower plant species diversity in the dry season compared to ungrazed Kikandekande site (P < 0.01), unlike in the wet season when there was no significant difference in plant species diversity. CCA analysis showed that nitrate, organic matter and soil moisture influenced plant species distribution at P < 0.024 while soil texture, phosphate and pH influenced plant species distribution at P < 0.002 in both seasons. Though not critical, the BD of 1.2 g cm-3 with BD as high as 1.58 g cm-3 and 1.64 g cm-3 localized at some points in grazed sites, acted synergistically with OM, soil gravimetric moisture, grazing stress and soil texture to influence plant species composition and distribution in the study sites. Soil bulk density ranged from 0.24 g cm-3 to 1.01 g cm-3 at the control Kikandekande site while at grazed Kiberege and Lungongole sites BD was 1.2 g cm-3 an indication of grazing pressure. Phosphate, ammonium and nitrate concentration in the dry season was 0.109 ± 0.03 mg L-1 and 0.626 ± 0.26 mg L-1 at Kiberege and Lungongole sites, respectively. During the wet season phosphate concentration in the water was 0.063 ± 0.03 mg L-1 and 0.3 ± 0.19 mg L-1 at Kiberege and Lungongole, respectively. Intensive grazing in the Kilombero Ramsar site has affected both water and soil physico-chemical parameters. Grazing stresses including soil compaction, disturbance and plant overconsumption have synergistically affected plant species diversity and distribution. This led to low plant species diversity in the heavily grazed Lungongole site in the dry season. For sustainable resource use in the Kilombero Ramsar site, it is recommended that the flood plain should be designated as ‘‘conservation area’’ and later on a ‘‘national park’’. This will enhance conservation status of the fauna and flora in the flood plain and rescue the resources therein from further deterioration.
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    Influence of sewage pollutions at ocean road beach on the marine environment
    (University of Dar es Salaam, 2005) Frederk, Godfrey
    The objective of this study was to explore some physical, chemical and biotic parameters at polluted Ocean Beach and compare them with those at a relatively unpolluted Mbweni beach. A total of 50 sampling stations were established along 5 transects at each beach. Benthic macrofauna were obtained by sieving sand through 1 mm mesh and identified in the laboratory. In the laboratory nutrients were determined spectrophotometrically. Salinity, pH and turbidity were measured by refractometer, pH-meter and portable spectrophotometer, respectively. Student t-test showed that nitrate concentration in the sediments and biodiversity of macrofauna were higher at Mbweni beach (p ˂ 0.05) compared to Ocean Road beach. Turbidity and pH were higher at Ocean Road beach (p ˂ 0.05) compared to Mbweni. Ammonium, nitrate and phosphate concentrations in the water column were higher at Ocean Road beach (p ˂ 0.0001) than Mbweni. Phosphate and ammonium concentration was higher in the sediment pore water at Ocean Road beach (p ˂ 0.05) compare to Mbweni. The pore water content in the sediments at Ocean Road beach was higher than Mbweni beach (p ˂ 0.0001). This study concluded that pollution by sewage at Ocean Road beach has elevated some physical parameters like turbidity, pH and BOD and lowered salinity at Ocean Road beach. Marine pollution has adversely impacted macrofauna at Ocean Road beach by reducing their diversity and altered their composition. Some parameters like turbidity decreased seawards from pollution point Ocean Road beach, indicating direct impact of sewage pollution.