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

splitting. The higher DBH classes were found in inaccessible sites that are protected from anthropozoogenic
impact. The absence of the first DBH class in the lower subzone could be related to the
species’ reproductive biology, as seeds need light and warm soil for germination (Lange et al. 1997);
grazing pressure may also have some impact. The relatively high incidence of class-1 in the upper
subzone (Fig. 1e), and H. abyssinica‘s complete absence from the central subzone, indicates the
potential of the species to grow in higher altitudes than the current treeline (i.e. above 3600 m asl.).
Hypericum revolutum shows an irregular size class distribution in the lower subzone (Fig.
1f). In the central subzone the higher diameter classes are completely absent (Fig. 1g). This species
is preferentially used for construction of pillars for traditional huts (because of its straight stem); its
numerous branches make it ideal for constructing walls. The species is not represented at all in the
upper subzone.
Myrsine melanophloeos shows an inverted ‘J- shaped distribution (Fig. 1h and 1i). The density
of the species decreases with increasing diameter indicating good regeneration and reproduction.
The limited palatability of the species contributes to survival of saplings and explains the high
density in the first DBH class. The absence of individuals in class 2, 7, 8 in the lower subzone and
3, 7, 8, 10 in the central zone might indicate selective removal of individuals. Farmers prefer the
species for fire wood because it gives high heat, less smoke and a persistent flame.
Schefflera volkensii shows an unhealthy size class distribution being represented only in four
DBH classes (3, 4, 6 and 10) in the lower subzone (Fig. 1j). It is the second most preferred species
by the locals for fuel, because the wood burns slowly but persistently and is often used to maintain
the fire over night. The absence of the species in the central and upper subzone might be due to its
altitudinal limit, i.e. due to some physiological constraint.
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 166