Part II Effects of Fire on Mountain Biodiversity 3523_book.fm Page 23 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC 25 2 Diversity of Afroalpine Vegetation and Ecology of Treeline Species in the Bale Mountains, Ethiopia, and the Influence of Fire Masresha Fetene, Yoseph Assefa, Menassie Gashaw, Zerihun Woldu, and Erwin Beck INTRODUCTION Uplift and volcanism in the Miocene and Oli- gocene geological periods (between 38 and 7 million BP) resulted in the covering of all the underlying rocks and the formation of the East African mountains that rest like islands on the surrounding hills and plains. These Afromon- tane archipelagos are distributed on both sides of the East African Rift Valley. The Bale Mountains lie in the southeastern part of the Ethiopian highlands, about 850 km north of the equator. The highest peak in Bale, Tulu Dimtu, is the second highest peak in Ethiopia and the sev- enth in Africa (see Figure 2.1). The East African mountain nearest to the Bale mountains is Mt. Kulal, 550 km south in the Turkana Depression. The vegetation of the Bale Mountains has been the subject of studies by a number of bot- anists and ecologists. A full account of the his- tory of botanical exploration of the Bale Moun- tains has been provided by Miehe and Miehe (1994). In a series of publications, Hedberg (1975, 1986) made important analyses of the vegetation and ecology of Afroalpine regions in Ethiopia. Weinert (1981), Weinert and Mazurek (1984), and Uhlig (1988) also conducted eco- logical research on the vegetation of the Bale Mountains. Miehe and Miehe (1994) presented a detailed study on ericaceous vegetation and on the plant communities within the ericaceous zones of the Bale Mountains. The present study attempts to provide a description of plant com- munities in the entire altitudinal range of the Afroalpine and ericaceous zones. The ericaceous belt of the Bale Mountains is a region most seriously affected by the pro- gressive increase of human activities. Cattle and horses put heavy pressure on the vegetation, especially at the lower altitudes. The ericaceous bushes are cut for fuel wood and are frequently burned by the local people for various reasons. This results in the destruction of the vegetation and in the disappearance of the fauna, and hence leads to a reduction of the region’s biodiversity. The present study aims at (1) describing the plant communities of the Afroalpine and erica- ceous zones, (2) documenting the distribution patterns of treeline species and the changes in the structure of ericaceous vegetation with alti- tude, and (3) assessing the incidence and influ- ence of fire on the diversity and composition of vegetation in the ericaceous belt. MATERIAL AND METHODS D ESCRIPTION OF THE S TUDY A REA Geology and Climate The study area is the Harenna Escarpment, located at the southern slopes of the Bale Moun- tains between 6 ° 45 and 7 ° N and 39 ° 45 and 3523_book.fm Page 25 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC 26 Land Use Change and Mountain Biodiversity 39 ° 40 E. The rocks of the volcanic outpourings are predominantly trachytes but also include rhyolites, basalts, and associated agglomerates and tuffs. Although adequate information about glaciations is lacking, the current landforms in the mountains appear to have resulted from actions of tectonics and glaciations. At least two glacial periods are documented in the moun- tains (18,000 BP and 2,000 BP, Bonnefille, 1993). In contrast to the northern highlands, south- ern Ethiopia is within the East African climatic domain, which is highly influenced by south- easterlies from the Indian Ocean during most of the year. As in most Ethiopian highlands, the intertropical convergence zone (ITCZ) and local altitudinal and topographic influences affect the distribution of the precipitation in the Bale Mountains. Annual rainfall in the Bale Mountains ranges between 600 and 1500 mm depending on the relief (see Table 2.1). The diurnal variability in temperature in the Bale Mountains is higher than the seasonal vari- ation. A minimum temperature of − 15 ° C was recorded by Hillman (1986) on the Sanetti Pla- teau (3850 m), whereas Miehe and Miehe (1994) recorded a nocturnal minimum temper- ature of – 3°C in sparsely vegetated areas of the ericaceous belt. Solifluction is common in the FIGURE 2.1 Map of the study area. (From Miehe and Miehe [1994].) 3523_book.fm Page 26 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC Diversity of Afroalpine Vegetation and the Influence of Fire 27 Afroalpine area and in the upper parts of the ericaceous vegetation. Recently, the ericaceous and the Afroalpine areas have been subjected to increasing grazing pressure. The number of livestock varies in the wet and dry seasons (the maximum is 46/km 2 in the plateau and minimum is less than 2/km 2 ) (Hilman, 1986; Gottelli and Sillerio-Zubiri, 1992). Poaching of mountain nyalas and small antelopes is also common in the area. These activities are accompanied by deliberate setting of bush fires for hunting, and clearing and improvement of pastures (Miehe and Miehe, 1994). There is evidence of early settlements in some valleys and plains in the area. Recently, with the construction of an all-weather road tra- versing the plateau, there is an increase in barley cultivation in the ericaceous and Afroalpine veg- etation. However, the highlands of the Bale Mountains are still less densely populated than the Semien Mountains of northwestern Ethiopia (see Table 2.2). For instance, barley is cultivated in Bale at 600 to 800 m lower than in Semien. This is due to the transhumant mode of living in the Bale Mountains. V EGETATION S AMPLING The current study considers vegetation in the ericaceous belt of the Bale Mountains along an altitudinal gradient ranging from 3000 to 4200 m. Transects were laid out based on homoge- neity of the vegetation (Mueller-Dombois and Ellenberg, 1974). Relevés of 15 m × 15 m size were established at 50-m vertical distance (alti- tude). Within each altitudinal level, replicate relevés were put with minimum lateral distance of 20 m. Within each relevé, a subplot of 2 m × 2 m was made for the herbaceous vegetation. All vascular plants in each relevé were recorded. We estimated abundance for single species using the 9-level ordinal cover abun- dance scale following Braun Blanquet as mod- ified by Van der Maarel (Van der Maarel, 1979). The height of trees and shrub species, diameter at breast height (DBH) for trees, and the diam- eter at stump height (DSH) for shrubs were also recorded in all relevés. S OIL AND E NVIRONMENTAL D ATA The rainfall measurements were compiled for the time of fieldwork and for the previous 11 months. Climate data of the area from previous studies were also considered (Miehe and Miehe, 1994). For each plot, information on altitude, slope, inclination, soil surface, and vegetation cover, etc., were collected. Soil sam- ples were collected from the topsoil and at a depth of 30 cm from the surface of each relevé. Soil moisture, texture, pH, and total nitrogen were determined for each sample. I NCIDENCE OF F IRE Records on incidence of recent fires were gath- ered. In addition to the information obtained from the local people, the incidence of fire was assessed from the presence or absence of Bryum argenteum (a moss that grows after fire), char- coal, and remnants of charred twigs and ligno- tubers. The presences of each of these indicators were summed for each relevés, yielding a com- bined index of fire incidence. TABLE 2.1 Annual rainfall for northern (n) and southern (s) slopes of Bale Mountains and on Sanetti Plateau (P) Locality Altitude (masl) Rainfall (mm) Years Chorchora (n) 3500 1086 1985–1991 Goba (n) 2720 925 1968–1980 Koromi (P) 3850 1051 1985–1991 Mena (s) 1250 387 1983–1988 Rira (s) 3000 848 1987–1990 Tulu Konteh (P) 4050 852 1985–1991 Source: From Hilman (1986); Miehe and Miehe (1994) . 3523_book.fm Page 27 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC 28 Land Use Change and Mountain Biodiversity D ATA A NALYSIS Vegetation data were analyzed with hierarchical syntax clustering using agglomerative method with optimization (Podani, 2000). A resem- blance matrix was calculated with the similarity ratio: S ij = 1- ∑ i xij xik / ( ∑ i xij2 + ∑ i xik2 - ∑ i xij xik ) where S ( i , j ) in row i and column j is the distance between observations i and j . Species-wise cover abundance values were used to classify vegeta- tion communities. In classifying the communi- ties, the subject group averages were used to eval- uate the degree of dissimilarities among the relevés. Both the vegetation data and the environ- mental variables were analyzed with canonical correspondence analysis (CCA) using CANOCO (ter Braak and Smilaur, 1998) to explore the cor- relation between vegetation and environmental variables. Species richness and relative abun- dance were analyzed using the Shannon–Weaver index of diversity (Krebs, 1989). RESULTS AND DISCUSSION P LANT C OMMUNITIES The southern slope of the Harenna Escarpment with its montane forest between 1500 and 2800 m is more gentle than the ericaceous vegetation above this altitude. The Bale Mountains have high floral and faunal diversity as well as ende- micity. The floristic composition of the area has been reported by Friis (1986); Hedberg (1986); Negatu and Tadesse (1986); Woldu et al. (1989); Gashaw and Fetene (1996); and Bussman (1997). A total of 60 relevés were sampled at the northwestern side of the Bale Mountains. The hierarchical classification gave six major plant communities. The first of these is the Knipho- fia– Euphorbia–Alchemilla community (3400 to 3500 m). In this community, Kniphofia foli- osa , Euphorbia dumalis , and Alchemilla abys- sinica were the characteristic species. At the next altitudinal level, we find the Alchemilla haumannii community (3700 to 4000 m). This community is dominated by A. haumannii , which sometimes forms pure stands. On the southeastern side of the Bale Mountains, a total of 110 relevés were sam- pled, in which 84 species of vascular plants were encountered. Eight of these were trees and shrubs, and the rest were herbaceous plants. The ericaceous vegetation was grouped into three altitudinal subzones fol- lowing previous works: lower subzone (3000 to 3400 masl), central subzone (3400 to 3600 masl), and the upper subzone (3600 to 4000 masl) (see also Hedberg, 1951; Miehe and Miehe, 1994). Thirteen community types were identified from the cluster analysis. The communities were named based on the spe- TABLE 2.2 Population density in Semien and Bale Mountains (persons/km 2 ) based on the census data taken for each zone (district) and the woredas (subdistricts) circumscribed by the mountains Zone/Woreda Year 1998 1999 2000 Semien Mountains North Gondar zone 49.8 51.2 52.6 Debark 91.7 94.4 97 Bale Mountains Bale zone 22.1 22.7 23.4 Kokosa 160 164.5 169 Dodola 91.2 94 96.9 Adaba 52.2 53.7 55.3 Sinana Dinsho 90.3 93.2 96.2 Goba 44 45.8 47.6 Menana Harenna Bulqi 14.1 14.5 14.9 Source: Central Statistical Authority (2001). 3523_book.fm Page 28 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC Diversity of Afroalpine Vegetation and the Influence of Fire 29 cies with the highest cover abundance. The distribution of the communities varied in the lower (3000 to 3400 m), central (3400 to 3600 m), and upper (3600 to 4200 m) subzones of the ericaceous belt. Some of the community types occurred in the entire altitudinal range (3000 to 4200 m), whereas others were restricted to certain ranges. Plant diversity showed an inverse bell-shaped pattern. The upper and the lower subzones had higher diversities than the central one. The complete list of the communities and their respective distribution, diversity, and evenness in the three subzones are given in Table 2.3. The Schefflera volkensii – Erica trim- era–Discopodium penninervium community (altitude range, 3100 to 3300 m) is found at the lowermost part of the ericaceous subzone. The emergent tree in this community is Schefflera volkensii. Higher up in the lower ericaceous subzones, the Erica trimera–Hagenia abyssin- ica–Hypericum revolutum community occurs. The characteristic species for this community are Erica trimera, Trifolium acaule , Hypericum revolutum , Hagenia abyssinica , and Discopo- dium penninervium . At lower altitudes (between 3000 and 3200 m), this community forms a subcommunity that is characterized by the dominance of Hagenia abyssinica and Hypericum revolutum . Another community also common at the lower subzone of the ericaceous belt is the Erica trimera–Polystichum–Hyperi- cum revolutum community (Plate 2.1a). The characteristic species of this community include Erica trimera , the codominant tree Hypericum revolutum , the most common fern Polystichum sp., Discopodium penninervium , and Cynoglossum amplifolium. At the central subzone of the ericaceous belt, we find the Erica trimera–Hypericum revolutum – Alchemilla abyssinca community. In this community, the dominance of Erica trimera is conspicuous in the upper layer of the canopy. Another community of the central subzone is the Erica trimera–Cynoglossum amplifolium–Discopodium penninervium community. Among communities of the upper subzone, we find the Haplocarpha rueppellii–Alchemilla microbetula–Alchemilla pedata community (3300 to 3900 m) and the Satureja para- doxa–Asplenium aethiopicium-Geranium ara- bicum community. In the former, Haplocarpha rueppellii , Alchemilla microbetula , Alchemilla pedata , Myosotis abyssinica , and Discopodium penninervium are the characteristic species, whereas the characteristic species in the latter community are Satureja paradoxa , Asplenium aethiopicium , Geranium arabicum , Crepis rueppellii , and Stachys aculeolata. The upper part of the ericaceous belt had a patchy appear- ance with more openings. Depending on the microsite factors, the diversity was comparable with the lower part (2.35 ± 0.048 for the lower and 2.10 ± 0.05 for the upper) and was greater than in the central subzones. D ENSITY AND F REQUENCY OF T REELINE S PECIES A total of eight tree and shrub species were recorded, out of which Erica trimera was found in almost all relevés, whereas one spe- cies ( Pittosporum viridiflorum ) was recorded in one relevé only and is not shown in Figure 2.2. Erica trimera and Hypericum revolutum showed similar trends in frequency in the lower and central subzone (Figure 2.2). H. revolutum was absent in the upper part of the ericaceous subzone. At the lower ericaceous subzone, the frequency of E. trimera was lower because of the competitive strength of the other montane woodland species (Miehe and Miehe, 1994). However, it is an important component of all three subzones of the erica- ceous belt and no other species, including Erica arborea, showed such a wide distribu- tion. Erica arborea was not found below 3200 m. Rapanea melanophloeos, H. revolutum, and D. penninervium were constituents of both the lower and central subzone but not of the upper subzone. Schefflera volkensii is restricted to the lower part of the ericaceous belt, and Hagenia abyssinica attained its high- est frequency in the lower subzone. The den- sity of the treeline species showed a similar trend as the frequency. The height of treeline species decreased with increasing altitude (Table 2.4). The most notable change was observed for E. trimera. The regression analysis (Figure 2.3) showed a strong inverse relation between altitude and height (R 2 = 0.60). This could be attributed to the decrease in temperature with increasing alti- tude. 3523_book.fm Page 29 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC 30 Land Use Change and Mountain Biodiversity TABLE 2.3 The distribution of the diversity (H), evenness of the 13 community types, and a verage value for incidence of fire in lower, central, and upper subzones of ericaceous vegetation Distribution Diversity Fire Incidence Community Types Lower (3000–3400) Central (3400–3600) Upper (3600–4200) Species Number Shannon Index Evenness Index: 1 Erica trimera–Hagenia abyssinica–Hypericum revolutum + + 17 2.23 0.96 1.3 2 Erica trimera–Polystichum sp.–Hypericum revolutum + + – 13 2.11 0.95 0.5 3 Erica trimera–Hypericum revolutum–Alchemilla abyssinica + + – 13 2.36 0.97 0.6 4 Erica trimera–Cynoglossum amplifolium–Discopodium penninervium – + – 8 2.43 0.99 1.0 5 Schefflera volkensii–Erica trimera–Discopodium penninervium + – 5 2.54 0.97 1.2 6 Senecio fresenii–Alchemilla abyssinica–Cynoglossum amplifolium + + – 2 2.47 0.99 0.0 7 Erica trimera–Luzula johnstonii–Geranium arabicum + + – 9 1.89 0.94 0.8 8 Lotus discolor–Polystichum sp.–Schefflera volkensii + – – 2 2.31 0.96 0.0 9 Haplocarpha rueppellii–Alchemilla microbetula–Alchemilla pedata + + + 12 2.11 0.95 0.8 10 Alchemilla fischeri–Luzula abyssinica–Cineraria abyssinica + + + 15 2.21 0.97 0.1 11 Festuca richardii–Dryopteris inaequalis–Alchemilla haumanni – + + 3 2.42 0.97 1.3 12 Alchemilla pedata–Asplenium aethiopicum–Alchemilla abyssinica – + 9 2.29 0.97 0.1 13 Satureja paradoxa–Asplenium aethiopicum–Geranium arabicum – – + 2 0.81 0.42 2.0 Note: + indicates presence and − is absence. 3523_book.fm Page 30 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC Diversity of Afroalpine Vegetation and the Influence of Fire 31 FIGURE 2.2 Frequency of treeline species in three ericaceous subzones: Schefflera volkensii (SV); Rapanea melanophloeos (RM); Hypericum revolutum (HR); Discopodium penninervium (DP); Hagenia abyssinica (HA); Erica trimera (ET); Erica arborea (EA). The three ericaceous subzones are the lower (3000 to 3400 masl); middle (3400 to 3600 masl); and upper (3600 to 4000 masl) zones. TABLE 2.4 Height and DBH of five treeline species at (1) lower, 3000–3400 m, (2) central, 3400–3600 m, and (3) upper, 3600–4200 m, subzones of the ericaceous belt in Harenna Escarpment, Bale Mountains Species Subzones DBH Height Number of Stems D. penninervium 1 2.23 ± 1.90 119 2 1.75 ± 1.28 3——— E. arborea 1 — 1.62 ± 1.20 106 2 4.04 ± 0 1.12 ± 0.80 3 — 0.95 ± 0 E. trimera 1 23.34 ± 7.44 10.19 ± 2.20 255 2 12.32 ± 12.38 5.30 ± 4.53 3 10.00 ± 8.20 2.08 ± 1.98 H. revolutum 1 26.75 ± 8.83 13.60 ± 3.37 96 2 16.74 ± 10.11 7.37 ± 5.86 3—— R. melanophloeos 1 25.02 ± 9.49 16.50 ± 6.87 91 2 14.34 ± 7.81 8.96 ± 6.60 3—— 0 20 40 60 80 100 Frequency SV RM HR DP HA ET EA 3600-4200 m 3400-3600 m 3000-3400 m 3523_book.fm Page 31 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC 32 Land Use Change and Mountain Biodiversity RELATIONS BETWEEN DISTRIBUTION AND E COLOGICAL CHARACTERS OF TREELINE S PECIES AND THEIR ENVIRONMENTAL F ACTORS The Pearson correlation analysis revealed a strong positive correlation between altitude and slope (0.8) and an even stronger negative cor- relation between altitude and pH. Percent silt and clay showed negative correlations at r = − 0.6 and −0.4, respectively. The correlation coef- ficients of the environmental parameters are given in Table 2.5. An ordination biplot was made for all envi- ronmental variables. The biplot diagram of the FIGURE 2.3 Biplot diagram showing the correlations of environmental parameters in the canonical ordination space. TABLE 2.5 Pearson’s correlation coefficient matrix for the nine environmental variables Altitude Slope Aspect Moisture pH N Fire Sand Clay Slope 0.725 Aspect −0.001 −0.216 Moisture −0.33 −0.299 0.668 pH −0.785 0.629 −0.206 −0.375 N 0.028 0.129 −0.066 0.013 −0.196 Fire 0.512 0.411 0.476 0.224 0.100 −0.564 Sand 0.638 0.871 −0.349 −0.457 0.637 0.226 0.150 Clay −0.201 −0.469 0.554 0.202 −0.480 −0.338 0.186 −0.418 Silt −0.605 −0.733 0.126 0.41 −0.475 −0.089 −0.248 −0.902 −0.014 Note: The magnitude indicates the degree of correlation. Positive signs indicate positive correlation and negative signs indicate inverse relation. Numbers in bold indicate significant correlation at p < 0.05. Altitude (m) 2800 3000 3200 3400 3600 3800 4000 4200 Height (m) 0 5 10 15 20 3523_book.fm Page 32 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC Diversity of Afroalpine Vegetation and the Influence of Fire 33 environmental variables reflects approximately the Pearson’s correlation coefficients (Figure 2.4). RECENT INCIDENCE OF FIRE Recent incidence of fire showed an increasing tendency with increasing altitude (Figure 2.5). Fire incidence was not common in rocky areas with big boulders. The incidence was lower in areas with high cover of epiphytes, due, per- haps, to the convective cloud from Harenna that leads to the formation of thick epiphytic cover, playing a crucial role in insulation. Highly dis- turbed sites were avoided intentionally in this study. However, even in the relatively less dis- turbed vegetation, there was some evidence for recent occurrence of fire, especially at the upper subzone of the ericaceous vegetation. Incidence of fire was more common at the upper part of the ericaceous vegetation. This is an indication that fire had little influence on the physiognomy of the lower part of ericaceous vegetation. This is in agreement with other investigations (Wesche, 2002). The highest incidence of fire was recorded in the Satureja paradoxa–Asple- nium aethiopicum–Geranium arabicum com- munity at the upper subzone of the ericaceous vegetation. The absence of indicators for fire incidence in the Senecio fresenii–Alchemilla abyssinica–Cynoglos-sum amplifolium com- munity does not necessarily show the complete absence of fire in those localities. Alternatively, it may indicate the disappearance of the indi- cators of fire, which might be due to more severe disturbance. FIGURE 2.4 Regression analysis of the correlation of average height of E. trimera with altitude. 3523_book.fm Page 33 Tuesday, November 22, 2005 11:23 AM Copyright © 2006 Taylor & Francis Group, LLC [...]... vegetation and lifeform types, climatic features, and influence of fire on the vegetation were studied with particular emphasis on the distribution and ecology of treeline species The major plant community types on the northwestern side of the mountain are the Kniphofia–Euphorbia–Alchemilla scrub 3 523 _book.fm Page 36 Tuesday, November 22 , 20 05 11 :23 AM 36 Land Use Change and Mountain Biodiversity PLATE 2. 1A... palatable species (Kniphofia–Euphorbia community) dominates with severe grazing and fire (a) is taken on the southern slope, whereas (b) and (c) are from the northwestern slope of the mountain Copyright © 20 06 Taylor & Francis Group, LLC 3 523 _book.fm Page 38 Tuesday, November 22 , 20 05 11 :23 AM 38 Land Use Change and Mountain Biodiversity community, Alchemilla haumannii meadow, Helichrysum citrispinum–Alchemilla...3 523 _book.fm Page 34 Tuesday, November 22 , 20 05 11 :23 AM 34 Land Use Change and Mountain Biodiversity IMPLICATIONS OF INCIDENCE VEGETATION DYNAMICS OF FIRE TO Data collected from various sources (see Table 2. 6) indicate that occurrence of fire in the Bale Mountains is very frequent In the present study, samples were taken preferentially where there was a more or less undisturbed, continuous, and homogeneous... (1975) Studies of adaptation and speciation in the Afroalpine flora of Ethiopia S Boissiera 24 : 71–74 Kerbs, C.J (1989) Ecological Methodology Harper and Row, New York Miehe, S and Miehe, G (1994) Ericaceous Forests and Heathlands in Bale Mountains of South Ethiopia Ecology and Man’s Impact Traute Warnke Verlag, Hamburg, Germany Mueller-Dombois, D and Ellenberg, H (1974) Aims and Methods of Vegetation... plots of average height of E trimera at three subzones, and the incidence of fire for southeastern transect (median and interquartile range) Copyright © 20 06 Taylor & Francis Group, LLC 3 523 _book.fm Page 35 Tuesday, November 22 , 20 05 11 :23 AM Diversity of Afroalpine Vegetation and the Influence of Fire 35 TABLE 2. 6 History of Fire Incidence in the Bale Mountains Area Year Locality Burnt Area Months Northwestern... frequent fires and high grazing pressure seem to have nduced a transition in the plant community composition (see Plate 2. 1b) This transition is usually from the Erica trimera–Helichysum citrispinum community to the Euphorbia dumalis–Kniphofia foliosa community as a result of Average height of Erica (m) 16 14 12 10 8 6 4 2 0 Fire scale 4 3 2 1 0 300 0-3 400 m 340 0-3 600 m 360 0-4 20 0 m FIGURE 2. 5 Box and Whisker... Mazurek, A (1984) Notes on vegetation and soil in Bale province of Ethiopia Feddes Repertorium 95: 373–380 Weinert, E (1981) Vegetation in Bale mountains near Goba S Ethiopia Wiss Z Univ Halle 32: 41–67 Wesche, K (20 02) The high-altitude environment of Mt Elgon (Uganda, Kenya) — climate, vegetation and the impact of fire Ecotropical Monogr 2: 1 25 3 Woldu, Z., Feuli, E., and Negatu, L (1989) Partitioning... measured January/March 19 92 Different areas, Toroshoma: Adelay and Not measured Early April Gasuray 19 92 Gajera Not measured Early April 1993–1994 Batu Tiko and Gurari around two spots on But less than 19 92 December/February Sanetti plateau, Adely ridge around Simbirro, and 1993 and other areas 1998 Northeastern and southwestern parts of the Bale 150,000 ha December/April Mountains and Borena aData gathered... are from the northwestern slope of the mountain Copyright © 20 06 Taylor & Francis Group, LLC 3 523 _book.fm Page 37 Tuesday, November 22 , 20 05 11 :23 AM Diversity of Afroalpine Vegetation and the Influence of Fire 37 PLATE 2. 1C (a) The relatively little-disturbed ericaceous forest at the southern slope of the Bale Mountains; (b) expansion of the cushion form Helichrysum sp community replacing the ericaceous... community at the central and upper altitudes Microclimate and site conditions had high influence on diversity and life-form features Fire incidence was very frequent and had a serious influence on the diversity Incidence of recent fire increased with increasing altitude Fire caused the expansion of secondary vegetation and encroachment of weeds such as Euphorbia dumalis, Kniphofia foliosa, and Solanum aculeatum . Moun- tains between 6 ° 45 and 7 ° N and 39 ° 45 and 3 523 _book.fm Page 25 Tuesday, November 22 , 20 05 11 :23 AM Copyright © 20 06 Taylor & Francis Group, LLC 26 Land Use Change. increasing alti- tude. 3 523 _book.fm Page 29 Tuesday, November 22 , 20 05 11 :23 AM Copyright © 20 06 Taylor & Francis Group, LLC 30 Land Use Change and Mountain Biodiversity TABLE 2. 3 The distribution. ± 2. 20 25 5 2 12. 32 ± 12. 38 5.30 ± 4.53 3 10.00 ± 8 .20 2. 08 ± 1.98 H. revolutum 1 26 .75 ± 8.83 13.60 ± 3.37 96 2 16.74 ± 10.11 7.37 ± 5.86 3—— R. melanophloeos 1 25 . 02 ± 9.49 16.50 ± 6.87 91 2