Abstract
<p>Progressive loss of productivity and plant diversity is a major in global rangelands. In African rangelands ecosystems, this process is partly attributed to heavy and uncontrolled grazing by livestock and wildlife, leading to land degradation. Therefore, restoring such degraded rangelands is critical for enhancing ecosystem health and securing the livelihoods of millions of people. Active restoration strategies, e.g. reseeding using indigenous perennial grasses has been identified as a viable ecological solution for restoring degraded African rangelands. Grass species indigenous to African rangelands Cenchrus ciliaris L. (African foxtail grass), Eragrostis superba Peyr. (Maasai love grass), Enteropogon macrostachyus (Hochst. Ex A. Rich.) Monro ex Benth. (Bush rye grass), Chloris roxburghiana Schult. (Horsetail grass) and Chloris gayana Kunth. cv Boma (Rhodes grass) were established in a semi-arid rangeland in Africa under natural conditions to compare their morphoecological characteristics and suitability for use in ecological restoration. Biomass dry matter yields, plant densities, basal cover, seed production, tiller densities and plant height were measured. Chloris gayana cv Boma and E. superba produced significantly higher dry matter biomass yields and seed production than other species. High biomass and seed production demonstrate their suitability to support livestock production and replenish depleted soil seed banks, respectively. Enteropogon macrostachyus and C. ciliaris displayed significantly higher values for plant densities, tiller densities and basal cover, also a component of establishment and ecological restoration success. Chloris roxburghiana ranked lowest in all the measured morphoecological characteristics. This may be a strong indicator of ecological site-specific characteristic of C. roxburghiana. Successful restoration of degraded African semi-arid rangelands using indigenous grass reseeding can best be achieved through careful selection of grasses to take advantage of their specific morphoecological characteristics. This selection should primarily be informed by the intended use of the rangeland.</p>
Highlights
In Africa, arid and semi-arid rangelands cover about 41% of the continent’s landmass and are characterized by low, erratic annual rainfall (300–600 mm), high temperatures and nutrient poor soils (Sanchez, 2002; Vohland & Barry, 2009)
Seedling emergence was fastest in E. macrostachyus and slowest in C. roxburghiana (Table 1)
Plant height after 9 months was negatively correlated with plant density (R = 0.72, p < 0.001) and basal cover (R = 0.73, p < 0.001), but positively correlated with seed production (R = 0.66, p < 0.001) and dry matter biomass yields (R = 0.83, p < 0.001) (Figure 3)
Summary
In Africa, arid and semi-arid rangelands cover about 41% of the continent’s landmass and are characterized by low, erratic annual rainfall (300–600 mm), high temperatures and nutrient poor soils (Sanchez, 2002; Vohland & Barry, 2009). For example, Themeda triandra Forssk., Cynodon dactylon (L.) Pers., Chloris roxburghiana Schult., Cenchrus ciliaris L., Enteropogon macrostachyus Panicum coloratum L., provide a rich source of forage for grazing livestock and wildlife (Koech et al, 2016; Mnene et al, 2005). Degradation caused by heavy grazing causes major ecological transformation and negatively impacts the three broad attributes of rangeland health, that is, soil and site stability, hydrologic function and biotic integrity (Duniway & Herrick, 2013; Herrick et al, 2017 ; Whisenant, 1999). More active restoration procedures, for example, reseeding using native perennial grasses, have been incorporated into rangeland restoration (Kimiti et al, 2017; Kinyua et al, 2010; Koech et al, 2016; Mganga et al, 2015; Mnene et al, 2005). Use of native grass seeds for reseeding is advantageous because of their better survival and growth, reduced risk of restoration failure due to poor adaptation to local environmental conditions, limiting ‘pollution’ of local gene pools and outbreeding depression (Broadhurst et al, 2008)
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