Do Bush Control Techniques Have an Effect on the Density, Cover and Recruitment of Woody Plants in a Semi-Arid Savanna? The Case of a Semi-Arid Savanna, Southern Ethiopia

High bush density and cover have negative effects on the environment in general and on livestock production, in particular in savanna rangelands. The study examined the effects of bush control techniques on woody sapling recruitment in the low land savanna region. The study consisted of 21 plots located next to each other on an area of 5.3 ha encroached by Acacia mellifera and Acacia reficiens trees. Seven bush control treatments were assigned randomly to the plots and replicated three times. In the bush clearing plot, woody species were removed at ground level using a handsaw. In the tree thinning; thinning and grazing; thinning and browsing; thinning and fire, and thinning with fire-browsing treatments, trees were thinned to the equivalents of 60% of the density of that of the control plot. Positive changes in sapling densities were observed in the clearing, thinning, and thinning and grazing treatments. In contrast, the control, thinning and browsing, and thinning and fire treatments presented negative changes in densities. A change in sapling density was highest in the cleared plot, whereas it was lowest in the thinning, fire, and browsing treatment. The correlation between changes in sapling densities and new recruitments was highly (p < 0.001) significant in the clearing, thinning, and thinning and grazing treatments thus increased sapling recruitment with the proportion greater for the clearing treatment. The significant correlation induced average sapling recruitment in the control, and low in the thinning with browsing and thinning with fire treatments. The relationship was insignificant in the thinning, fire, and browsing combination treatment and resulted in the lowest rate of saplings’ recruitment. Postthinning techniques reduced woody tree recruitment and would sustain open savanna under the continuous management plan.

COMPLEMENTARY ANALYTICAL TECHNIQUES PAPER, THIN-LAYER, HIDE-POWER, AND COMBINED METHODS FOR CHARACTERIZATIONOF TANNIN IN PLANTS

The polyphenolic compoundsextract rich in gallo-catechol tannins submitted to complementary analytical techniqueswas evaluated. The whole plantspecies screened were of the condensed type except Acacia seyal var. fistuala, Acaciaseyal var. seyal, Casuarina equistifolia, and Pithecellobium dulcewere of mixedhydrolysable-condensed(gallo-catechol) type. The quantitative data indicated that 5 parts (bark) out of 12 species, when extracted, contained more than 10% tannins (oven-dry basis), the level of commercial interest. The catechin numbers indicated that all the studied species contained condensed tannin in varying amounts (0.6-45.7), while the presence of both gallic acid and catechin means that the tannin is of mixed type. Thin-layer and paper chromatography with different solvent systems confirmed the presence of catechin and gallic acid, and showed that tannic acid, fisetin, epicatechin and some unidentified phenolics were present. However, dihydrofisetin and robinetin, which were used as standards, were not detected. Astringency values shows that the Acacia mellifera(0.18), Acacia seyalvar.fistuala(0.18), Pithecellobium dulce (0.15), Acacia senegal (0.14), Acacia farnesiana (0.13), Calotropis procera (0.13)barks could be used in place of A. mearnsii(international commercial tannin materials) (0.16) because the degree of relative astringency or the ability of their tannin to combine with protein is close to that of A. mearnsii in other words these six species can give leather with characteristics comparable with that of A. mearnsii.

The Use of Seed Vigour Tests for Predicting Field Emergence

The general aim of this study was to address the problem of seed vigour testing in Acacia senegal and Acacia mellifera) by studying different seed vigour tests and comparing them to identify the most suitable test for each species. The importance of this study lies in the fact that vigour testing measures the percentage of viable seeds in a sample as well as their ability to produce normal seedlings under less than optimum or adverse growing conditions, similar to those occurring in the field. To achieve this objective, a set of laboratory and field tests were conducted for the two Acacia species. Data collected included: The number of seeds per kilogram, germination percentage, seedling shoot length, seedling root length, seedling root wet and dry weight, seedling shoot wet and dry weight. The cutting test, electrical conductivity tetrazolium test and Hiltner test were employed to determine the seed vigour. The results showed that Acacia mellifera had a high electrical conductivity, indicating its low seed vigour. The electrical conductivity of Acacia senegal was equivalent to that of distilled water, indicating that either the seed coat was intact or no ions were leached from the seeds. Comparison of the various tests suggests that Hiltner test is the most accurate” or “reliable”) test for seed vigor.

Antiinflammatory, analgesic and antipyretic effects of dichloromethane stem bark extract of Acacia mellifera

The present study was designed to assess the in vivo antiinflammatory, analgesic and antipyretic effect of the dichloromethane stem bark extract of Acacia mellifera on experimental animal model at three different dose levels of 50, 100 and 150mg/kg body weight respectively. In addition, phytochemical screening of the extract was done. The inflammatory effect was evaluated by use of carragenaan-induced paw edema in mice, pain was determined using formalin-induced writhing in mice and pyrexia was determined by turpentine-induced pyrexia in rats. The activity of the herbal extract was compared to diclofenac sodium and aspirin. The phytochemical analysis showed the presence of alkaloids, cardiac glycosides, flavonoid, saponins, steroids, terpenoids, tannins and phenolics. The plant extract produced marked anti-inflammatory effect in carrageenaninduced mice paw edema assay, suppressed licking response of animals in both phases of the formalin- induced test and exhibited appreciable antipyretic effects in turpentine-induced pyrexia in rats. The study thus supports the folklore use of the plant in the treatment and management of inflammation, pain and pyrexia.

Cross-amplification and Characterization of Polymorphic Microsatellite Markers From Acacia (Senegalia) mellifera and Acacia brevispica to Acacia senegal (L.) Willd.

Seven polymorphic microsatellite markers isolated from Acacia brevispica and Acacia mellifera were successfully cross-amplified in Acacia senegal. The loci were surveyed for polymorphism using 30 samples. Allelic diversity ranged from 4 (Ame02, Ab06 and Ab18) to 13 (Ab26) per locus. The expected heterozygosity (HE) ranged from 0.543 (Ame02) to 0.868 (Ab26) while observed heterozygosity (HO) ranged from 0.516 (Ame05) to 0.800 (Ame03). Cross-amplification of these loci represents a potential source of co-dominant markers and will be useful in the study of genetic diversity, structure, gene flow and breeding systems of this important Acacia species.