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3. METHODS 3.1 Sampling and Data Collection

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In Laelay Maychew woreda, based on source of quarry materials (stone) and access to urban area (mainly to Axum), the quarry sites were grouped in to five clusters. Based on simple random selection two clusters were selected (cluster Mahibereselam and
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  3. METHODS 3.1 Sampling and Data Collection In Laelay Maychew woreda, based on source of quarry materials (stone) and access to urban area (mainly to Axum), the quarry sites were grouped in to five clusters. Based on simple random selection two clusters were selected (cluster Mahibereselam and Dura). From the two selected clusters, purposely one watershed from each was selected for this study (Maygundi and Duragobodura). Duragobodura and Maygundi watersheds are among the quarry areas found in tabia Dura and Mahiberselam respectively. The watersheds are bestowed with natural and human planted vegetations as well as large reserve of stone resources (Table 4.1) 3.2 Existing Land Use The watersheds were mapped in the field using a GeoExplorer III GPS (Trimble Navigation Limited, Sunnyvale, CA), and mapped in Arc View GIS 3.2 (ESRI, Redlands, CA) with other spatial data digitized from a topographic map (1438-D3 Axum, and 1438-D4 Adwa, Ethiopian Mapping Authority, Addis Ababa). Contemporary land use was assessed by means of detailed Global Positioning System (GPS) measurements. The positions of prominent point and linear features such as large trees, boulders, gullies, contour stone bunds, and footpaths were recorded for further use as ground control points (GCPs). A 2011 land-use map was prepared (Figure3.3) and its attribute information is prepared in (Table 3.2). Information about former land use and land-use changes was derived from semi-structured interviews with 10 purposively selected resident senior farmers . 3.3 Species Abundance, Density, Diversity and Similarity The vegetation characteristics in quarry and non-quarry areas of Maygundi and Duragobodura watershed were studied during July to December 2011. To study the impact of stone quarry on vegetation; transect line according to gradient analysis was carried (Letheren, 2008). In this method, vegetation was considered in the area around the quarry to a radius distance of 200m from the quarry centre. Vegetation sampling through line transects was laid out, and the lines were parallel to each other (Birhane, 2002). The distance between two consecutive parallel transect lines was 20m vertical interval. Along transect lines, sample quadrate measuring 20 m X 20 m (400 m2) were laid down at 50m interval from each other. The quadrates were established using a plastic ribbon and four wooden pegs.  Based on the above conditions; in Maygundi watershed in the northern part of the watershed along the hill downward there are two enclosures on similar topographic position (  Endazabuo and Adisendel  ) on the one stone extracted along the upper hill tips (  Endazabu o) and the other one(  Adisendel  ) with no any stone extraction. On these two sites three transect lines each were laid (upper, middle, and lower) and a total of 36 sample plots on quarry site and 36 sample  plots on non-quarry site was laid. The overall sample plots for trees, shrubs, and herbaceous was 72plots. Likewise, in Duragobodura watershed in twined sub watershed; one quarry and other non-quarry (out of or very low stone extraction) three transect line on each site 66 plots (33 in quarry and 33 in non-quarry). In each quadrate: (I) the identity of all woody plants were determined and the total number as well as height of individuals (using a graduated stick and clinometers) of each species was recorded; (II) the diameters of saplings and trees was measured just above the ground (basal diameter) and at 0.5 m, respectively using a caliper and diameter tape. For regenerated seedlings (height < 0.5 m), only their number was recorded. Individual woody categorization was made as height < 0.5m and dbh <2.5 cm seedling, h >0.5 m and dbh <5 cm sapling and h >0.5 m and dbh> 5 cm tree. Plants on the plot boarder were included if 50% or greater of the area covered by the plant fell within the plots. Species present and the percentage of the 2mx2m sub-plot covered by each species were recorded. Where there were 10 plants or less the number  present were recorded. More than 10 plants was recorded in categories of >10, >20 or >50. For species that was difficult to identify in the field, herbarium specimens were collected,  pressed, dried and transported to the Herbarium in the Department of Biology, Aksum University, for proper identification. Quantitative community characteristics such as frequency, density, basal area, important value index (IVI) of each species were determined following Misra (1968) and Muller Dombois and Ellenberg (1974). The sum of all species encountered in the quadrates of both the vegetation on the quarry and the vegetation on non-quarry sites were used to determine the species richness in the study sites. Similarly, the abundance of each woody species, was defined as the total number of all individuals of a species in all the quadrates either within the vegetation surrounding the quarry, i.e. individuals to the total area of the quadrates (27600m 2 ), or vegetation on non-quarry sites, i.e. individuals to the total area of the quadrates (27600m 2 ), were calculated. Then, the density of each woody species in both study sites was determined by converting the total number of individuals of the species encountered in all the quadrates to a unit area of one hectare  (individuals/ha). The frequency of each woody species was calculated by determining the  proportion of quadrates in which the species would be encountered (Birhane, 2002). The basal area of each woody species was calculated using the formula (Kent and Coker, 1992): BA= πD2/4………………………………………………………………………………  (1) Where; BA= basal area (tree cross sectional area), D= diameter of the tree (diameter of the cross section) The Important Value Index (IVI) of a given species is the sum of the relative abundance, using the relative basal area (basal area species X /sum of basal area for all species)*100), relative density (density species X /sum of density of all species)*100 and relative frequency (freq. species X /sum of frequencies for all species)*100 the sum of which provides. The diversity values of woody plants in the quarry (Q) and non-quarry (NQ) area will be calculated using diversity indices, species richness, evenness and heterogeneity (Krebs, 1999, Magurran, 1996). The total numbers of species were taken as a measure of richness, where as the Simpson and Shannon indices taken as a measure of heterogeneity. Indices based on species number and numbers of individuals was calculated based on: Margalefs (Dmg) index (Magurran, 1996) given by Dmg=(S- 1)/lnN …………………………………………………………………  (2) Mehinicks index (Magurran, 1996) was given by Dmn =S/√N………………………………………………………………………  (3) Where S, total number of species recorded & N, is total number of individuals recorded. Measures of heterogeneity used: The Berger  –   Parker index (Magurran, 1996), which expresses the proportional importance of The most abundant species was given by d=Nmax /N. …... ............................................................................................... (4)   Where, Nmax is the number of individuals in the most abundant species. It‘s reciproc al is used as the measure of diversity index. Simpson index (D) given by D=∑ (ni (ni -1))/N (N- 1) ………………………………………………………….. (5)  Where ni is the number of individuals of the ith species and  N the total number of individuals D used as an index of dominance and its inverse is an index of diversity: 1/D Shannon diversity index (Magurran, 1996) can be calculated by H = - ∑ pi ln pi……………………………………………………………………. . (6) Where pi is the proportional abundance of the ith species =ni/N The Shannon evenness was calculated as; SE=H/ lnS …................ ............................................................................................ (7) Where S is the total number of species recorded. The variance of H was calculated; Var= (∑pi (lnpi) 2 –    (∑pi ln pi ) 2 / N)  –   S- 1/2N2…………………………………  (8) A t- test was allowed the diversity of the VSQ & VNQ to be compared. The appropriate formula was; t= H1- H2 / (VarH1 + VarH2)1/2=…………………………………................ (9) Where H1 is diversity of site 1 and Var H1 is its variance. The degree of freedom will be calculated using df = (VarH1 + VarH2) 2 / [(VarH1) 2/N1 + (VarH2) 2/N2]………………… (10) Where N1 is the number of individuals. Estimators of species richness:   Jacknife technique given as (Magurran, 1996) J = S + {S1 (2N-3) /N-S2 (N-2)/N (N- 1)} ……………………………………… .. (11) Where S1 is the number of individuals represented by a single individual and S2 the number of individuals represented by two individuals. The other estimator of species richness was the Chaos (C) index given by C = S + [S1/ S 2]………………………………………………………………. (12) Where S1 and S2 are the total number of individuals represented by one and two individuals respectively. Similarity indices Between the two land management (Q & NQ), the standing vegetation was analyses using Sorenson’s measure of similarity (quantitative data) (Magurran, 1996) given as   CS=2jN/ (aN + bN) ………………………………………………………………  (13) Where aN the number of individuals in site A, & bN the number of individuals in site B, &  jN = the sum of the lower of the two abundances of species which occur in the quarry and non-quarry area. 3.4 Ground Cover of Herbs To estimate the abundance of herbaceous species in the around the quarry, a small plot measuring 2m x 2m(4m 2 ) was placed in the middle of each of the big quadrates(20m x20m). In this plot, the proportions of cover by each herbaceous species were estimated visually (Birhane, 2002, Sutherland, 2000). 3.5 Soil Chemical and Physical Properties Determination Composite soil sample from four corners and the centre of each sample quadrates, were collected from the upper 0  –  20 cm of the soil layer, and from the 138 sample quadrates (72 Maygundi and 66 Duragobodura), 138 soil sample (from sample quadrates) was collected, and these samples were grouped according to transect line in to twelve soil sample groups. Each of sample groups was mixed thoroughly in a large bucket to form a composite soil sample, which was transported to the laboratory for further analysis. Plant roots and shoots were handpicked
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