Walia Special Edition on the Bale Mountains (2011) - Zoologische ...

The Bale Mountains National Park is part of Conservation International’s Eastern
Afromontane Biodiversity Hotspot and is on the tentative nomination for World Heritage Site
Listing. The park houses a number of rare and endemic species (Asefa this edition), such as the
mountain nyala Tragelaphus buxtoni (Malcolm and Evangelista this edition), the Ethiopian wolf
Canis simensis (Randall et al. this edition; Sillero-Zubiri et al. this edition), the giant mole rat
Tachyoryctes macrocephalus and the giant lobelia Lobelia rhynchopetalum.
Generally, the study area is characterized by five distinct vegetation zones each of which
harbor its own fauna and flora. The Gaysay valley grasslands are situated within a broad flat valley
at an altitude of 2600-3000 m a.s.l. These grasslands, which are part of the northern projection of the
BMNP boundary, are dominated by Artemisia afra, Ferula communis, Kniphofia foliosa, grasses and
sedges, interspersed with wetlands (Hillman 1986; AAU 2004). The dry evergreen montane forest (or
Gaysay woodland) is also at the northern end of the park and situated 2600 and 3800 m a.s.l. The
lower altitudes are dominated either by Juniperus procera or Hagenia abyssinica with the two species
sometimes co-dominating on slopes. Other species that are not dominant but of significance include
Hypericum revolutum, Myrsine melanophloeos, Erica arborea and Discopodium eremanthum. The
higher altitudes dominated by Hypericum revolutum, Erica arborea between, and Helichrysum
citrispinum and H. splendidum moorland (Hillman 1986; AAU 2004). The central massif of the park
consists of an Afroalpine plateau between about 3200 and 4377 m a.s.l. The area between 3550 and
4000 m a.s.l is covered by Erica shrub on ridges and Helichrysum moorland in the valleys (Assefa
et al. this edition). The highest plateau areas are characterized by H. citrispinum and H. splendidum
while the endemic giant lobelia is scattered across the landscape. At lower altitudes (3200 – 3500
m a.s.l.) such as in the Web Valley and Morebawa, the Afroalpine habitat is characterized by short,
herbaceous plant communities dominated by Alchemilla (A. abyssinica, A. rothii, A. cyclophylla)
pasture, Helichrysum (H. citrispinum, H. cyosum, H. gofense, H. splendidum) shrubs and Artemesia
afra shrubs (Hillman 1986; Sillero-Zubiri 1994; AAU 2004). The Ericaceous belt, composed mainly
of Erica arborea and E. trimera, is located between 3200-3800 m a.s.l. and forms an important
vegetation belt between the high altitude Afroalpine plateau and the lower Harenna forest (Assefa
et al. this edition). Both shrub and tree forms are present, as well as the remnants of ancient forests
of giant heath (Erica arborea) in areas spared from excessive fire (Miehe and Miehe 1994). The
Harenna moist montane forest, rising from 1450 to 3200 m a.s.l. within a distance of only 8 km, is one
of the most extensive and largely natural forests remaining in Ethiopia. It is subdivided into a number
of altitudinal belts based on differences in tree species composition across the altitudinal gradient (Friis
1986; Woldu et al. 1989).
Satellite image acquisition and preparation
We used three types of satellite images in the study; Landsat MSS, Landsat ETM+ and ASTER (see
Table 1 for specifications). The Landsat images were acquired from the Global Land Cover Facility
(GLCF; www.glcf.org) through their Earth Science Data Interface (ESDI), whereas the ASTER was
downloaded from the USGS online data provision interface (http://edc.usgs.gov/products/satellite/
aster.html).
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