Ecological and Ethnomedicinal Study in Hirmi Woodland Vegetation and the Surrounding Districts Tigray Regional State Northern Ethiopia
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Date
2021-08-07
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Addis Ababa University
Abstract
Drylands in Ethiopia cover a substantial area endowed with diverse plant resources. However, the landmass has received less attention compared to the moist highlands even if it has high ecological, environmental and economic importance. The present study was conducted in dryland area of Hirmi woodland vegetation to investigate the floristic composition, vegetation structure, regeneration potential of the vegetation and to document the associated ethnomedicinal knowledge of the surrounding community. Vegetation and environmental data were collected from 80 sample plots with a size of 25 m × 25 m designated as the main plots. All vascular plant species were recorded. Woody species ≥ 2 m were counted, cover-abundance values estimated and Diameter at breast height were measured. A total of 128 soil samples were collected from four land use types to investigate the regeneration potential of the study vegetation. The ethnomedicinal data were collected using semi-structured interviews, guided field walks and focus group discussions. A total of 335 informants selected through stratified random and purposive sampling participated to document data related to the use and management of medicinal plants. Shannon-wiener diversity index, cluster analysis and ordination were computed on ecological data using R-software packages. Composition, density, depth distribution and Jaccard's coefficient of similarity were computed for soil seed bank analysis. Ethnobotanical analytical tools including preference ranking, informant consensus factor, direct matrix ranking and t-tests in SPSS were employed. A total of 201 vascular plant species belonging to 163 genera and 66 plant families were recorded. Of these 5% of the total recorded species were endemic/nearly endemic to Ethiopia while 10% of the species were new records to Tigray floristic region. In terms of species number, the dominant plant families were Fabaceae (13.9%), Poaceae (10.5%), Asteraceae (6 %) and Lamiaceae (5.5%). Five plant communities were identified in the study vegetation, namely; Ziziphus mucronata - Acacia polyacantha, Combretum hartmannianum - Terminalia macroptera - Oxytenanthera abyssinica, Anogeissus leiocarpa - Ozoroa insignis, Euclea racemosa - Acacia abyssinica and Dodonaea angustifolia- Flueggea virosa. The ordination result revealed that the identified five plant communities were associated with altitude, slope, sand, silt, soil organic matter, total Nitrogen and disturbance. According to the vegetation structure result, large numbers of individual species were categorized in the lower classes of DBH and height. Anogeissus leiocarpa, Combretum hartmannianum, Ziziphus mucronata, Terminalia macroptera and Acacia polyacantha were the species with high importance value. Some endemic plant species of Hirmi were found recorded in the IUCN red list. The overall regeneration status of the study area was found to be poor. This is attributed to anthropogenic disturbances and grazing pressures. A total of 58 species representing 51 genera and 22 families were recovered from the soil seed bank. Of these, 86.2% were herbs. The total density of soil seed banks from all land-use types was 3,116.7 seeds/m2. The highest species composition was found in the shrubland and the least number of species were found in the bare land. About 85 medicinal plant species used for the treatment of 71 human and 16 livestock ailments were documented. The majority (64.7%) of the medicinal
plants were collected from the wild environment, while the remaining (35.3%) were collected from the homegardens, fallow land and farming lands of the community. The highest informant consensus factor values were calculated for abdominal discomfort. Zehneria scabra, Plumbago zeylanica and Zingiber officinale were the most preferred medicinal plants to treat abdominal diseases. Regarding ethnomedicinal knowledge, there was a significant difference between age groups, educational status, marital status and experience of informants; however, religion and gender did not exert statistically significant differences. Overgrazing, deforestation and expansion of agriculture are the number one threats to the medicinal plants. Homegardening, fencing and plantation were among the conservation techniques used by the local community. In general, the study area is under poor regeneration status. To overcome this challenge, integrated management measures including monitoring, education and application of restoration techniques by taking into consideration the significant environmental factors associated with species diversity, IUCN threat level, ethnomedicinal services, regeneration potential and status of species are recommended to preserve and restore the study vegetation.
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Dryland, Ethnomedicinal Services, Floristic Composition, Hirmi, Regeneration Status, Soil Seed Bank, Tigray Floristic Region, Vegetation Structure