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.