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

The aim of this study was to examine the soil, vegetation and land use history in glades
across the altitudinal gradient present in the Harenna to characterize them by examining their soil
properties, and comparing these with soils in adjacent forest areas to investigate their origins.
Methods
Study site
The Harenna forest (approximately, 39’- 40’ E, 6’- 7’ N) is located in the southern part of the
Bale Mountains National Park (BMNP). The forest develops on an initially steep, then gradual
escarpment from ~3800 m a.s.l. to ~1600 m a.s.l.; the pronounced altitudinal gradient creates a
variety of forest ecotypes (Hillman 1988; Niatu et al. 1989; Woldu et al. 1989).
Mean annual rainfall at the southern end of the forest (Delo Mena, ~1500 m a.s.l.) is 987 mm
(Tesfaye et al. 2002) and reaches a maximum of 1145 mm in Koromi (3850 m a.s.l.) (Hillman 1988).
There are typically eight rainy months (March-October) and four dry months (November-February)
in a given year. The soils are derived from volcanic parent material, originating from Mesozoic
eruptions of Trappean lava giving trachitic, basaltic and riolitic bedrocks, together with tuffs and
agglomerates (Nigatu et al. 1989).
Sampling design
The study area was divided in to three sampling strata, located at different positions on the
toposequence, reflecting both altitudinal variation and variation of position along the direction of
groundwater movement (Fig. 1; 2400 m a.s.l., 1850 m a.s.l., 1750 m a.s.l.; hereafter S-2400, S-1850,
S-1750). The horizontal distance between S-2400 and S-1850 was about 6 km; the distance between
S-1850 and S-1750 was about 8 km. Three forest glades with adjacent forested areas, were chosen in
each strata, selection was based on accessibility (Table 1). Position and altitude of the glades were
recorded using a GPS and an altimeter, respectively. Adjacent forest sites were chosen randomly at
a distance between 50 m and 100 m from the edge of the glade. Fieldwork was undertaken during
the rainy season between begin of July and end of August 2006.
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 132