Species richness and composition
In the study area, a total of 47 herbaceous species were recorded. The herbaceous species richness was significantly higher (ANOVA: F = 60.61, df = 2, p < 0.001) in the enclosure land sites compared to the grazing and browsing sites. The Shannon diversity index for herbaceous species was estimated at 3.07, 2.92, and 2.78 for the enclosure, grazing, and browsing areas, respectively. On the other hand, the woody species richness was significantly lower (ANOVA: F = 13.61, df = 2, p < 0.001) in the enclosure land sites compared to the grazing and browsing sites (Table 1). The Shannon diversity index for woody species was estimated at 1.22, 1.36, and 1.25 for the enclosure, grazing, and browsing areas, respectively.
The distribution of herbaceous species composition varied significantly (ANOVA: F = 11.145, df = 2, permutations = 999, p < 0.001) among sites with different grazing management practices. The CCA analysis (Figure 3) showed some clear clustering of herbaceous species in association with the different grazing management practices. Notably,Chrysopogon aucheri, Chlor is gayana, Digitaria abyssinicum , and Themeda triandera species were widely distributed in the enclosure management sites. Whereas Tragus berteronianus and Eragrostis sp. species were highly distributed in the open grazing sites. In contrast, Abutilon fruticosum, Hibiscus asperhook , and Tragus racemosus species were more prevalent in the browsing management sites (Figure 3).
The distribution of desirable herbaceous species was greater in the enclosure’s sites than in other management sites (Table 2). Among herbaceous species, desirable species of Chloris gayana, Chrysopogon aucheri, Cynodon dactylon, and Themeda triandera were distributed by 88.9%, 100%, 64.00%, and 93.33% respectively in the enclosure sites. In contrast, the distribution of undesirable herbaceous species was higher in grazing and browsing sites than in the enclosure sites. In the browsing site the less desirable species of Tragus racemosus and Sida sp were highly distributed by 56.67% and 46.67% respectively.
Moreover, we identified a total of five Acacia species and one Vachellia species. The composition of these woody species varied significantly (ANOSIM: R = 0.58, permutations = 999, p < 0.001) depending on the type of grazing management practices implemented in the area.Acacia etbaica was the dominant species in the browsing (Bay) management sites. Whereas Acacia busie was the dominant species in the enclosure and open grazing sites respectively (Table 3).