Effect of rangeland rehabilitation on the herbaceous species composition and diversity in Suswa catchment, Narok County, Kenya

Abstract

Introduction: Land degradation is a serious environmental problem of our time. In Kenya, it is estimated that 30% of the total land mass is severely degraded. Suswa catchment within Narok County is a good example with gullies of over 25 m deep and 30 m wide. In response to the increasing land degradation in the area, the Sustainable Land Management (SLM) project rehabilitated the catchment through establishment of soil and water conservation structures such as cutoff drains, semicircular bunds, and water retention ditches. Despite the various rehabilitation approaches carried out, little research has been done to ascertain their effect on successful vegetation recovery. This coupled with the fact that many restoration approaches have failed in East Africa and Kenya in particular gave drive to the study. The objective of this study was to determine the effects of rangeland rehabilitation on herbaceous species composition and diversity in a severely degraded rangeland. Methods: To assess the diversity of aboveground herbaceous layer in the rehabilitated and degraded areas along a slope (upper, middle, and lower), line transect and quadrat count methods were used. Within each slope position, three 100-m-long transects were placed across the hill parallel to one another 30 m apart using a tape. The species hit, the closest species to the hit, and hits on bare ground were recorded. Along the same transects, 1-m 2 quadrats were placed 25 m apart and aboveground biomass determined by the use of the destructive method. In the determination of species richness, diversity, relative abundance, percentage cover, and species composition, the Shannon-Wiener diversity index was used. Data collected on vegetation attributes was subjected to analysis of variance (ANOVA) using Genstat and Tukey's HSD post hoc used in means separation where F values were significant. Results: The results showed that percent cover (74.67%), aboveground biomass (1459 kg/ha), relative abundance, richness, composition, and diversity of perennial grasses significantly (P ≤ 0.05) increased downslope and were higher in the rehabilitated area than in the degraded area. On the contrary, forbs and annual grasses were significantly (P ≤ 0.05) higher within the degraded area compared to the rehabilitated area and increased upslope.

Variation in plant functional groups indicates land degradation on the Tibetan Plateau

“…The α-diversity was higher in the degraded lands, especially in the land which presented higher grass and legume cover compared to the species loss in the previous studies 15 , 31 . It may be that the graminoids or legumes could benefit the vegetation or soil and establish higher species abundance as in the Greater Caucasus 2 , 38 .…”

“…At the same time, the alpine meadow degradation has been a hot topic in ecological studies 9 – 11 . However, previous studies have focused on vegetation productivity or vegetated cover 12 , 13 , community species diversity 14 , 15 , or soil nutrients 14 , 16 , 17 in degraded lands. Knowledge of the indicative plant functional group (PFG) in degraded alpine meadows is still rare 2 .…”

Exclosure land management for restoration of herbaceous species in degraded communal grazing lands in Southern Tigray

“…Selective grazing of palatable herbaceous plants by livestock enhances the growth of annuals and unpalatable herbaceous plants (Skarpe 1992) resulting in the decline of palatable species (Fensham et al 2010). On the contrary, annual grasses were higher within the CGL compared to the AE (Ombega et al 2017).…”

“…The CGL was highly dominated by forbs, this is in line with prior studies (e.g., Sternberg et al 2000;Mphinyane et al 2008;Kgosikoma 2011) reporting that herbaceous plants are highly responsive to grazing pressure. The dominance of forbs in the CGL could be attributed to poor land management as a result of overgrazing (Solomon, Snyman, and Smit 2007;Ombega et al 2017). Overgrazing affects the botanical composition by depressing the vigor and presence of dominant species, which then enables colonization by less competitive, but, grazing -tolerant plant species (Sternberg et al 2000;Ayana and Oba 2007;.…”

“…In AE, it is generally believed that all the land resources will be protected from degradation (Tefera 2001). The effects of AE on the recovery of woody species diversity, population structure, and regeneration status, restoration of soils, and restoration of ecosystem carbon stocks have been well studied (e.g., Kindeya 2003;Aerts et al 2004;Tefera et al 2005;Descheemaeker et al 2006;Muluberhan et al 2006;Yayneshet, Eik, and Moe 2009;Wolde and Aynekulu 2011;Wolde et al 2011b;Yayneshet 2011;Wolde and Mastewal 2013;Ombega et al 2017;Eltalib, Lazim, and Dawelbait 2018;Tsegay et al 2019;Tesfay, Anteneh, Tessema, 2019). In addition, in the Tigray region, Northern Ethiopia, some studies that were conducted earlier (Kindeya 2003;Aerts et al 2004;Tefera et al 2005;Muluberhan et al 2006;Yayneshet, Eik, and Moe 2009;Yayneshet 2011;Wolde and Mastewal 2013; were specifically trying to estimate the role of AE in the recovery of vegetation diversity without considering specifying indigenous palatable herbaceous species.…”