Vegetation on hill slopes in southern Wello, Ethiopia: Degradation and regeneration

Abstract

A study was made of the vegetation in southern Wello (Ethiopia) in relation to human impact and the environment. 65 sample plots were laid out and analysed with respect to the cover value of vascular plant species. Altitude, slope, aspect and estimates of grazing pressure for each plot were also recorded along with physical and chemical soil properties analysed for samples taken from each plot. The following environmental factors, isolated by forward selection, show correlation with the axes of Canonical Correspondence Analysis (CCA): altitude, grazing, pH, K, Ca, Mg, slope and aspect. Through hierarchical and non‐hierarchical clustering methods the vegetation was divided into eight types, from which one was secondary forest characterised by patch dominance of Juniperus procera and Olea europaea ssp. cuspidata. These forest patches are found at high altitude sites and because of their inaccessibility are usually characterised by low livestock density and consequently low grazing pressure. The presence of large boulders and stones in Podocarpus falcatus forest decreases accessibility and creates natural protection for the trees. The other vegetation types, most of which are found at lower altitude and associated with varying intensities of grazing, include grasslands (grazed and protected), regenerating sites dominated by Eu‐clea racemosa and Dodonaea angustifolia, dense and open shrublands and Olea europaea ssp. cuspidata woodlands. Human interference has a major impact on the vegetation of the study area and its recovery will depend on the degree of participation of the local people.

Land Degradation in the Ethiopian Highlands

“…Nowadays, changes in the agricultural system appear such as haymaking ('cut and carry') (Hurni 1986), partially from exclosures (i.e. land under strict conservation management, often controlled by the community), which are increasingly being organised in the most affected northern highlands (Tekle et al 1997;Shitarek et al 2001;Aerts et al 2004Aerts et al , 2009Descheemaeker et al 2006b) and which lead to sediment trapping and enhanced soil fertility status (Elias and Scoones 1999; Descheemaeker et al 2006a;Mekuria et al 2007).…”

Sediment deposition and pedogenesis in exclosures in the Tigray highlands, Ethiopia

“…The terms bexclosureQ and bclosed areaQ denominate the areas set aside, where agriculture and grazing became forbidden (Kebrom et al, 1997;Wisborg et al, 2000;Tenna et al, 2001;Aerts et al, 2001Aerts et al, , 2003. Exclosures are defined by Le Houérou (2000) as areas of natural vegetation protected from the intrusion of major degradation agents, such as humans, livestock and big game.…”

Floristic composition and plant community analysis of vegetation in Ilu Gelan district, West Shewa Zone of Oromia region, Central Ethiopia

“…Grazing intensity was estimated following Woldu & Backeus (1991) and Tekle et al (1997) as: 0= nil; 1= slight; 2= moderate and 3= heavy The state of human interference was estimated following Hadera (2000), Yeshitela & Bekele (2002), Kidane et al (2010) and codified using a 0-3 subjective scale to record the degree of the impacts (from cutting, fuel wood collection, charcoal production and sign of trampling) as: 0= nil; 1= low; 2= moderate and 3= heavy b. Vegetation data collection:…”