Native grass reseeding for restoring degraded African rangelands

Background/Question/Methods

Land degradation is a serious environmental problem in African rangelands exemplified by soil erosion and depleted vegetation. High degradation rates in African rangelands are attributed to the interaction of anthropogenic factors (e.g. grazing), land use change and biophysical factors (e.g. soil, climate, topography and vegetation). Subsequently, perennial grasses preferred by livestock are quickly disappearing leading to recurrent feed shortages threatening pastoralist’s livelihoods. Thus, restoring degraded African rangelands is critical for enhancing ecosystem health and securing the livelihoods. Active restoration strategies e.g. native grass reseeding and in-situ rainwater harvesting, have been identified as practical ecological solutions for restoring degraded African rangelands, enhancing vegetation cover and primary production. Perennial grasses adapted to African rangelands e.g. Cenchrus ciliaris, Eragrostis superba, Enteropogon macrostachyus, Chloris roxburghiana and Chloris gayana were established in semi-arid rangelands in Africa to determine their morphoecological characteristics, sensitivity to soil moisture availability and suitability for ecological restoration. Biomass dry matter yields, plant densities, basal cover, seed production, tiller densities, plant height, water use efficiencies, soil hydrological properties (runoff, infiltration and sediment production) were determined. This was aimed at establishing species specific characteristics of the grasses to address and combat explicit states and types of degradation in African rangelands.

Results/Conclusions

Chloris gayana and Eragrostis superba produced significantly higher biomass, water use efficiencies and seed production than other grasses. High biomass and seed production indicate their suitability to support livestock production and replenish depleted soil seed banks. Enteropogon macrostachyus and Cenchrus ciliaris displayed significantly higher values for successful ecological restoration i.e. plant densities, tiller densities and basal cover. Chloris roxburghiana ranked lowest in the measured morphoecological characteristics. The aggressive and allelopathic nature of Cenchrus ciliaris significantly supressed the weeds. In-situ rainwater harvesting enhanced soil moisture availability and displayed great potential for revegetating denuded semi-arid African rangelands. Sensitivity to soil moisture demonstrated by the magnitude to yield reduction during the growing season was in the order Eragrostis superba > Cenchrus ciliaris > Enteropogon macrostachyus. However, in terms of enhancing soil hydrological properties, the ranking was in the order Cenchrus ciliaris > Enteropogon macrostachyus > Eragrostis superba. Successful seed-based restoration of degraded African rangelands using native perennial grasses can best be achieved through careful selection and mix of grasses to take advantage of their specific traits. This selection should primarily be informed by the intended use of the rangeland and the specific challenges of restoring each site and match the desired restoration outcomes.