The Role of Area Exclosures for Soil and Woody Vegetation Rehabilitation in Hawzen District, Northern Ethiopia
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Date
2024-05
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Addis Ababa University
Abstract
Continuous loses of biodiversity and soil fertility in northern Ethiopia particularly the mid-highlands of Tigray have become serious threats as the consequences of anthropogenic processes. To overcome such problems, the government and peoples of Tigray Regional State has been practicing on soil and water conservation initiatives for decades. This study investigated the woody species composition, structure, regeneration, density and diversity in the area exclosure and in grazing area; and to assess the socioeconomic importance of area exclosure to the local communities. A total of 70 sample plots were used, 35 plots in exclosure and 35 in the grazing area.With in transects, nested quadrats having a size of 20 m × 20 m, 4m × 4m and 1m×1m were laid out to collect biophysical data. In each plot, heights, diameters and numbers of existing woody species were recorded. A total of 56 and 22 woody species were recorded in the Exclosure and Grazing area, respectively, belongs to 33 families in exclosure and14 families were recorded in the grazing area.The result showed that the densities (ha-1) of the woody species 1903 in the Exclosure and 30 In the Graznig ara were determined. Total basal area (m2ha-1) 71.01 for the Exclosure and 29.07 for the Grazing area were calculated Acacia albida and Acacia tortilis, Acacia etbaica woody species were the dominant species in the study site. High species richness was found in the Exclosure than the Grazing area. The population structures in each Exclosure were healthier and higher in recruitment potential than the adjacent Grazing area which was almost hampered. To assess the socioeconomic importance of the area exclosure, survey, and focus group discussions were made. The majority of the local people expressed a positive attitude towards the benefits of area exclosure in rehabilitation of woody species in the area. The impact of area exclosure on soil quality was assessed using soil physicochemical parameters such as soil organic matter, cation exchange capacity, total nitrogen, available potassium, available phosphorous, pH, electrical conductivity and texture. Fourteen soil samples were taken randomly from the two sites (7 from each), and analyzed. Soil laboratory analysis result revealed that the exclosure had significantly (p <0.05) higher levels for OM, CEC, TN, Av Ca,Av Mg and AvK compared to the grazing land.This showed that excluding degraded communal grazing lands from human and livestock disturbances is a viable option to restore degraded woody species in the mid-highlands of Tigray. To enhance the recruitment potential of some rare species, appropriate silvicultural practices are highly recommended for the Exclosure. Thus, wider promotion of exclosure in the region and across the nation should be guided by a scaling up strategy, formulated on the basis of lessons drawn from effective exclosure establishment and management practices.
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Keywords
Exclosure, Graing Area, Woody Species, Rehabilitation, Mid-Highlands of Tigray, Northern Ethiopia