Ecology and Development Series No. 10, 2003 - ZEF

Description of the study area and sampling designand all plants that had fruits and flowers during the survey were collected, identified anddeposited at the National Herbarium of Ethiopia (ETH), Addis Ababa University. The listof voucher specimens can be found in Appendix 8. The nomenclature of plant names inthis study follows the Flora of Ethiopia (Edwards et al. 1997, 2000; Hedberg and Edwards1989, 1995) and Cufodontis (1953-1972).Altitude, slope and aspect were recorded in the major plots. Geographicalpositions were also recorded in degrees and UTM at all major plots. Soil samples werecollected from the top 20 cm in each of the 9 m 2 subplots and mixed to obtain arepresentative sample for each plot. The samples were air-dried and passed through a 2 mmsieve prior to chemical and physical analysis, which were performed at the Water WorksDesign and Construction Enterprise (WWDCE) Soils lab, Ethiopia and the Institute forPlant Nutrition (IPN), the University of Bonn, following standard procedures (Allen 1989).At WWDCE, all soil samples were assayed for particle size distribution, percent moisture,CEC, available P, available K and pH and at IPN for C and N ratio. For the C-N ratioanalysis, an automated C-N analyzer (EURO EA Elemental Analyzer) was used.Abundance and frequency of all tree, shrub and climber species encountered in thestudy plots were compiled on a plot basis. Abundance is the number of stems per plot. Twosets of the abundance values were calculated, i.e., average abundance per plot wascalculated by dividing the sum of the number of stems of a species from all plots throughthe total number of plots (maximum frequency). Local abundance was calculated as theratio of the total number of stems of a species divided by its absolute frequency (as inGrace et al. 2000). Absolute frequency of a species is the number of plots in which thespecies was recorded. Relative frequency of a species is the ratio of absolute frequency ofthe species to the total number of study plots (which is equal to maximum frequency).The basal area (BA) was calculated for all species from diameter (D) at breastheight, using the formula BA = π (D/2) 2 . Average canopy cover was taken for each plot asa simple mean for the canopy cover estimate in each 9 m 2 subplot using a densiometer.Aspect, or the direction that a slope faces, was measured in degrees and transformedgeometrically to eastness (sin(aspect)) and northness (cos(aspect)) sensu Roberts (1986)and Palmer (1993).34