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

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Grasslands of the world
low palatability, they have wide adaptability to a broad range of environments.
Cenchrus grassland is often found associated with Aristida, or in Somalia
with Leptothrium (Herlocker, 1999), and has higher palatability and better
adaptation to hot dry areas with high evapotranspiration. Cenchrus is one of
the few grass genera that has been characterized for agronomic attributes. Over
300 ecotypes, mostly collected from Tanzania and Kenya, were characterized
for 12 agronomic attributes (Pengelly, Hacker and Eagles, 1992). The ecotypes
showed wide variability in their agronomic traits and were clustered into six
groups (Pengelly, Hacker and Eagles, 1992). The annual C. biflorus , which
is adapted to dryland areas, is also found in eastern Africa associated with
Schoenefeldia sp. and is typical of one dry area south of the Sahara in western
Eritrea (Herlocker, 1999).
Chrysopogon plumulosus is the most widespread species found in the semi -
desert grasslands and bushlands of the Horn of Africa (Herlocker, 1999) and is
avidly grazed, especially in Somalia and Sudan, where it is burnt to stimulate
regrowth for grazing . Chrysopogon is very sensitive to grazing. Overgrazing
results in elimination of the species and a change in species composition to
annuals such as Aristida spp. (Herlocker, 1999). This harsh management
regime in low rainfall areas has resulted in reduced stands of this grassland
in recent years (IBPGR, 1984). Herlocker (1999) recognized three zones in
the Chrysopogon region according to the associated woody vegetation . These
include Commiphora -Acacia bushland and Acacia etbaica open woodland,
which occur across the region, and the Acacia bussei open woodland in Somalia
and Ethiopia. He also recognized two subregions: the Cenchrus -Chloris subregion
in the wetter areas and the Sporobolus subregion in the drier areas. Rattray
(1960) recognized the Chloris areas as a vegetation type in its own right, and
included the Sporobolus as an associated grass in a Chrysopogon vegetation type
in very dry semi-desert areas of Somalia and Ethiopia.
Although not a vegetation type recognized by Herlocker (1999), Heteropogon
grassland is found in open woodland or grassland in the semi -arid and arid
rangelands in Somalia (Box, 1968), Kenya and Ethiopia. It is represented
mostly by H. contortus , which is commonly called spear grass due to its awns
and needle-sharp tips on the grass florets. It is a persistent species, which is
indigenous to the region, spreads rapidly through seed and grows in lowland
or middle altitudes with poor, stony, well drained soils. It is commonly found
with annual species of Aristida and Digitaria (Rattray, 1960). The species does
not have good palatability and is only useful when young.
Chloris roxburghiana is a dominant species in dryland areas of Kenya,
Ethiopia, Tanzania , Somalia and Uganda, and is usually found growing in
association with Chrysopogon aucheri and Cenchrus ciliaris in Commiphora
and Acacia woodland (Rattray, 1960). Despite its wide distribution, Herlocker
(1999) treats this vegetation type as a subtype of the Chrysopogon mid-grass
region. Chloris roxburghiana is widespread throughout the entire region and