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from grazing than in the open-grazed areas. Enclosures had higher herbaceous
species richness than the open-grazed rangelands and promoted the recovery
of some herbaceous species. The authors indicated that older enclosures had no
superior benefits over younger enclosures in terms of herbaceous production. The
exclusion for decades of fire as a diversifying factor in the savannas of southern
Ethiopia may have led to the loss of herbaceous species richness and diversity
(Angassa and Oba 2008).
The Borana used the communal rangelands for seasonal grazing that involved
livestock movements between the wet season and dry season grazing rangelands
(Coppock 1994). The Dida-Hara rangelands before the development of semipermanent
stock water ponds in the 1980s were part of the traditional wet season rangelands
exploited by the mobile fora herds (Oba et al. 2000; Homann and Rischkowsky
2005). The pastoral population has now settled in semipermanent settlements (Olla).
The mean livestock holding in Dida-Hara community is estimated at 12.6 cattle, 11.1
small ruminants, and 2.4 camels (Solomon et al. 2007), and the community adopted
semiprivate range enclosures to cope with periodic feed shortage for vulnerable ani-
mal class such as calves.
Overall, studies have shown a lack of significant difference owing to grazing
exclusion alone on SOC between grazed and ungrazed areas even for >30 years
(Aynekulu et al. 2014). Kieft (1994) observed similar results with lack of significant
differences in SOC between grazed lands and land not grazed for 11 and 16 years.
However, Reeder and Schuman (2002) reported greater SOC levels in grazed com-
pared with protected pastures in semiarid grasslands. The same authors noted that
under the exclosure system, there is immobilization of carbon in excessive above-
ground plant litter, and an increase in annual forbs and grasses that lack dense fibrous
rooting systems conducive to SOC formation and accumulation. Descheemaeker et
al. (2006) also studied grazing and exclusion areas established in different periods of
time (5, 14, and 20 years), and found higher biomass, potassium, phosphorus, SOC,
and soil nitrogen in exclusion areas.
African results differed from similar studies in other parts of the world in
which SOC was greater in exclusion areas compared with continuous grazing areas
(Schuman et al. 1999; Reeder et al. 2004; Mekuria et al. 2011; Sousa et al. 2012).
According to Reeder and Schuman (2002), differences in SOC contents in response
to grazing varied with climate conditions, soil properties, pasture location, vege-
tation community composition, and pasture management practices. Ingram et al.
(2008) found that SOC levels increased similarly for light and heavy grazed treat-
ments during the first 11 years of a long-term study conducted in Wyoming rela-
tive to an ungrazed control. However, SOC levels declined substantially during the
subsequent 10-year period (with increased drought) in the heavy grazed treatment,
but not the lightly grazed or ungrazed treatments. The SOC increase with moderate
grazing was in part the result of more rapid annual turnover and redistribution of
carbon within the plant-soil system and changes in plant species composition.
Stohlgren et al. (1999) concluded that for levels of grazing in Rocky Mountain
grasslands, (i) grazing probably had little effect on native species richness at land-
scape scales; (ii) grazing probably had little effect on the accelerated spread of most
exotic plant species at landscape scales; (iii) grazing affected local plant species
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