Discussion
In our study, we observed substantial disparities among the three
grazing management practices analyzed. In the following sections, we
will delve into these distinctions by examining the herbaceous
vegetation structure, woody vegetation structure, and vegetation biomass
associated with each practice. By providing a comprehensive overview of
these differences, we aim to highlight the implications of each
management strategy on the overall health and sustainability of
rangeland productivity and biodiversity conservation.
Herbaceous vegetation
structure
Herbaceous species accumulation estimates for enclosures, open grazing,
and browsing areas were 30, 24, and 20, respectively (Table 2). These
results are consistent with prior research (Angassa et al. 2010; Hailu
2016; Mekuria et al. 2018; Yayneshet, et al 2009), which demonstrated
the efficacy of enclosure management in improving rangeland vegetation.
Furthermore, the prevalence of preferred herbaceous species, such asChloris gayana, Chrysopogon aucheri, Cynodon dactylon, and Themeda
triandera , and Themeda triandera , was higher in enclosures than
in other management sites (Table 2). The decrease in these desirable
species under grazing and browsing management practices might be due to
overgrazing. Gemedo-Dalle et al. (2006) suggested that alterations in
community composition resulting from grazing pressure could signal
rangeland deterioration. Supporting this hypothesis, our study found a
greater distribution of undesirable herbaceous species in grazing and
browsing areas compared to enclosures. Similarly, Miehe et al. (2010)
observed a marked increase in low-quality herbaceous plants at a grazed
site relative to a non-grazed site in Senegal’s savannah ecosystem. The
current study’s finding of a higher proportion of perennial herbaceous
species in enclosure management sites aligns with Bilotta et al.
(2007), who reported that perennial species dominated lightly grazed
areas, while annual forbs and weedy species prevailed in heavily grazed
locations.
Apart from overgrazing, local elders in group discussions highlighted
recurring droughts as the primary factor contributing to the
deterioration of rangelands in the study area, a finding supported by
Kassahun et al. (2008). This degradation has resulted in the loss of
perennial, palatable, and productive grasses, essential for livestock
production in rangelands (Tuffa, 2022). In response, Somali pastoralists
have implemented rangeland enclosures, primarily aimed at preserving
forage during extended dry seasons or drought periods, while also
promoting conservation. Furthermore, these enclosures provide households
with the opportunity to generate income by selling pasture or hay.
Recent policy changes by the Somali Regional government have
reclassified private rangeland enclosures as communal land, as land
ownership in Ethiopia is vested in the government and the public.
Consequently, local communities have expressed their discontent and
resisted the regional government’s actions. Pastoral households with a
higher proportion of grazers are particularly inclined to claim
enclosures more than others (Fekadu Beyene, 2009). Successful
interventions, however, rely on the genuine engagement of pastoralists;
otherwise, negative consequences may arise.
Our study provides evidence that the establishment of enclosures in
response to periodic droughts, biodiversity conservation, and rangeland
productivity is an appropriate management strategy. Therefore, it is
essential to recognize the participation of pastoral communities in
environmental monitoring and decision-making as a fundamental aspect of
effective rangeland management. Their knowledge and its outcomes can
significantly contribute to the development of local policies (Oba,
2012).
Woody vegetation
structure
In our study area, woody species richness was found to be relatively
low, with only six species identified. This contrasts with the findings
from the Borona pastoral ecosystem of Ethiopia, where Tefera, Snyman,
and Smit (2007) documented approximately 54 woody plant species in the
Southern Ethiopian Borona rangelands. Similarly, Gilo and Kelkay (2017)
reported about 39 woody species within the same region. The pastoralists
in our study area are aware of the potential dangers posed by woody
species and often clear most shrubs and trees not favored by livestock
from their rangelands. This practice may contribute to the low species
richness observed in our. Moreover, during group discussions,
pastoralists in the study area expressed concerns regarding the threats
to native trees caused by the high reliance on fuelwood and charcoal.
Browsing land management practices appear to have a negative impact on
woody species richness and diversity, while also promoting higher
density levels. The average wood densities per hectare in browsing, open
grazing, and enclosure areas were estimated at 1125, 3742, and 50,
respectively. Woody vegetation canopy covers were approximately 94%,
30%, and 10% for browsing, open grazing and enclosure areas,
respectively. Numerous studies (Ayana Angassa & Oba, 2008; Gilo &
Kelkay, 2017; Gobelle & Gure, 2018; Tefera et al., 2007; Woods et al.,
2019; Yusuf et al., 2011) have demonstrated that, over the past century,
the balance between plant life forms has shifted in favor of trees and
shrubs across many East African rangelands. This transformation of open
grasslands into dense woody cover is referred to as bush encroachment,
which negatively affects understory herbaceous grass growth and hinders
human and livestock mobility (Angassa & Oba, 2010a; Dalle et al., 2006;
Walker et al., 1981). Undesirable woody species also pose a threat to
the biodiversity and stability of rangeland ecosystems (Gemedo, 2006).
Richter, Snyman, and Smit (2001) found that a density threshold of over
2500 tree equivalents per hectare is required for woody species to be
considered a bush encroachment risk.
In the current study, the density and canopy cover of woody species in
enclosure and open grazing areas were not extensive enough to be
classified as a woody-encroached state that significantly suppresses
herbaceous species. However, browsing land management practices
exhibited encroachment by wood vegetation layers, with canopy cover
estimated at 94%. Additionally, elders participating in group
discussions observed an increase in woody density and cover in communal
open grazing areas compared to past decades. Somali pastoralists view
this increase in wood density as indicative of rangeland degradation,
resulting in an imbalance in the grass-to-bush ratio, and consequently,
a decrease in palatable herbaceous species diversity and productivity.
Supporting this notion, the low number of herbaceous species richness in
browsing management practices in our study may be due to wood vegetation
encroachment. Furthermore, O’Rourke and van Wijngaarden (1987) noted
that grazing is eliminated in East African rangelands when bush cover
reaches 90%. In recent decades, the Borana plateau’s grazing system has
become increasingly unsuitable due to range degradation caused by woody
plant encroachment (Negasa et al. , 2014). As a result, Borana
pastoralists have transitioned from cattle herding to goat and camel
herding.
The long-standing practice of Somali pastoralists to diversify herd
composition based on patchy resource distribution and balance resource
utilization has proven to be an effective management decision.
Consequently, policymakers and extension workers should acknowledge and
incorporate pastoralists’ experiences and knowledge, which have been
utilized for generations to manage rangelands. Alternatively, they
should develop effective and applicable strategies for controlling woody
encroachment.
Vegetation biomass
The herbage biomass within enclosures was three times greater than in
open grazing areas and twice as much as in browsing land management
practices (Table 1). This increase in herbage biomass at enclosure
management sites may be attributed to the decrease in grazing pressure,
allowing for the accumulation of soil organic matter during rest
periods. Consistent with our findings, studies conducted in Borana and
other pastoral regions in Ethiopia have confirmed that periodically
resting grazing lands enables herbaceous forage species to regenerate
from the soil seed bank, thus increasing biomass yield (Behnke, 1986;
Abebe et al. , 2006; Angassa et al. , 2010; Abdulatife
Ibrahim, 2016; Mohammed, Abule and Lissahanwork, 2017; Nyberg et
al. , 2019). In contrast, the woody biomass in enclosures was
approximately half that of open grazing areas and five times less than
browsing land management practices (Table 1). This finding diverges from
Gilo and Kelkay (2017), who reported higher aboveground woody biomass in
enclosure management practices compared to other rangeland management
strategies in the Barona rangelands of Ethiopia. Gufu Oba et al., (2001)
similarly observed higher aboveground biomass in grazing enclosures than
in open grazing areas. Sawadogo et al., (2005) also noted a decline in
aboveground biomass under intensive grazing management when compared to
rangeland enclosures.