Grasslands of the World.pdf - Disasters and Conflicts - UNEP

The changing face of pastoral systems in grass-dominated ecosystems of eastern Africa 35
is an important species for livestock and wildlife . This species contributes up
to 50 percent of the diet of wild herbivores in eastern Kenya (IBPGR, 1984)
but is in danger of disappearing due to overgrazing and land degradation 2 . The
species is very variable. A recent study using random amplified polymorphic
DNA (RAPD) markers to study diversity among four populations from ecologically
distinct sites in eastern Kenya showed significant variation among the
populations (W.N. Mnene, KARI, Nairobi, pers. comm.).
Chloris gayana is an important native species and a component of the
Hyparrhenia type of grassland (Rattray, 1960) in open steppe and wooded
grassland vegetation or flooded valleys in the higher rainfall areas of Kenya,
Ethiopia, Tanzania , Somalia and Uganda. Herlocker (1999) considers this vegetation
type part of the Hyparrhenia-Hyperthelia tall-grass region of miombo
woodland. The miombo woodland is an important vegetation type covering
the southern two thirds of Tanzania. Chloris gayana, or Rhodes grass , is not
an important grass ecologically in the vegetation of the region, but is important
commercially as a forage grass. It shows wide adaptability with high palatability,
and is a fast-growing, persistent, frost- and drought -tolerant species valued
for grazing (Skerman and Riveros, 1990). Commercial cultivars of Rhodes
grass have been developed from genotypes collected in Kenya and grown in
the region since the 1930s (Boonman, 1997). An analysis of genetic diversity
in Chloris gayana using amplified fragment length polymorphisms (AFLPs)
revealed considerable variation between the diploid and tetraploid cultivars,
with genetic similarity ranging between 66 and 89 percent in the diploids and
63 and 87 percent in the tetraploids (Ubi, Komatsu and Fujimori, 2000).
Hyparrhenia is one of the most widespread grassland types in eastern
Africa , and this grassland region, which is characterized by woodlands and
wooded grasslands dominated by H. rufa , covers parts of Uganda, Kenya
and Ethiopia (Herlocker, 1999). Several other species of Hyparrhenia are
found in the region, of which the most important are H. hirta , H. diplandra
and H. filipendula . These tough perennial grasses are usually found growing
in combination with other grasses in woodland or open grassland, from the
lowland to mid-altitude areas. They are fast growing, and grazed while young,
but become tough and unpalatable as they mature and lose nutritive value
(Skerman and Riveros, 1990). Crude protein levels of H. dissoluta in Kenya can
decrease from over 14 percent to less than 3 percent after flowering (Dougall,
1960). After flowering, these grasses are much valued and used as thatching for
traditional rural housing, and mature grasses have commercial value, being sold
as standing grass to be cut for roofing in some rural areas. This and burning
ensure young regrowth with higher value for grazing in many areas. Grazing
2 In this chapter, we consider degraded land to be land that due to natural processes or human
activity is no longer able to sustain an economic function or the original ecological function,
or both (GLASOD, 1990).