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

The changing face of pastoral systems in grass-dominated ecosystems of eastern Africa 37
persistent and withstands severe defoliation and grazing . It is the dominant
species in natural pastures in many parts of the eastern Africa n highlands. It
is an invasive secondary species, which can quickly colonize disturbed soil in
cropping areas and fallow land, spreading by seeds or stolons, and may become
a serious weed in cropland (Boonman, 1993). It shows wide variability, with
three distinct ecotypes classified on leaf width and length, stolon size and floral
structure (Skerman and Riveros, 1990). Several ecotypes have been selected
as commercial cultivars, which have been widely introduced into tropical
highland and subtropical areas. It is now widely grown outside its native
distribution and is commonly cultivated in the Americas. Studies in the USA
using starch gel electrophoresis to describe the distribution of genetic variation
within and among introduced populations found a relatively high proportion
of polymorphic loci across populations, indicating fixed heterozygosity due to
polyploidy (Wilen et al., 1995). The highland grazing areas of P. clandestinum
are often mixed with P. sphacelatum and Eleusine floccifolia . These two grasses
are frequent in overgrazed pastures in the highlands and mid-altitudes in the
Rift Valley, but are not palatable (Sisay and Baars, 2002) and are important for
traditional basket making. Cattle avoid these grasses, which have the potential
to become major weeds on upland pastures unless collected for basket making.
Basket making is an important activity and source of income for rural women
and collection of these weedy grasses also maintains the quality of the communal
grazing areas and grasslands in the highlands.
Pennisetum purpureum is a tall, erect, vigorous perennial species that grows
in damp grasslands and forest areas up to 2 400 m in Kenya, Tanzania , Uganda
and Sudan. Herlocker (1999) recognized this as a vegetation region in Kenya
and Uganda, around the shores of Lake Victoria. Pennisetum purpureum
is widely distributed through sub-Saharan Africa and is commonly called
elephant grass or Napier grass, named after Colonel Napier of Bulawayo in
Zimbabwe, who promoted its use at the start of the century. It is now widely
used for cut-and-carry (where grass is collected by hand and carried to stallfed
cattle ) for the smallholder dairy industry in eastern Africa and frequently
produces up to 10–12 t/ha dry matter in rainfed conditions (Boonman, 1993).
Elephant grass is palatable when young and leafy. It is fast growing and should
be cut often to avoid its becoming tough and unpalatable with a high proportion
of stem. Due to its importance in the region, considerable research has been
done on elephant grass, including studies on its diversity. Tcacenco and Lance
(1992) studied 89 morphological characters on 9 genotypes of elephant grass to
determine which characters were most useful for description of the variation
in the species, and concluded that variation existed from plant to plant, even
within the same accession. A larger collection of 53 accessions was characterized
for 20 morphological and 8 agronomic characters (Van de Wouw, Hanson
and Leuthi, 1999). Again the germplasm was found to be very variable, but
accessions could be clustered into six groups with similar morphology. More