African Journal of Range and Forage Science

The impact of sheep grazing on shrub communities at the Afrikaner and Hereford grazing trials at Grootfontein in the Eastern Upper Karoo

L Hebbelmann, TG O’Connor, JCO du Toit — Thu, 26 Dec 2024 00:00:00 +0000

In the Nama-Karoo, grazing by livestock is an important driver of Karoo shrub composition. Many different breeds of livestock are farmed in the Nama-Karoo, and the stocking rate varies greatly over the region. In this study we examine how grazing by dorper and merino sheep applied at three stocking rates affected two Karoo shrublands on a long-term grazing trial at Grootfontein in the eastern Karoo. The effects of grazing treatment on shrub communities at two sites of the Afrikaner-Hereford grazing trial differed greatly and were measurable after ten years of rest. At the sandier, grassier Afrikaner site, heavy grazing by dorper sheep had a significant effect on shrub composition, density and cover, whereas the effect of grazing treatment was less pronounced at the Hereford site. Lenient grazing by merino sheep resulted in a vastly different community compared to all other grazing treatments. Individual Karoo shrub species responded differently to grazing treatment. Overall shrub recruitment has faltered for all but three species, and populations were dominated by intermediate-sized and large individuals. Results indicate that grazing management, animal type and stocking rate are important determinants of Nama-Karoo rangeland composition and structure with evidence of a legacy effect longer than ten years.

Vegetation diversity and composition in relation to different grazing intensity levels in an arid environment in Jordan

Salman D Al-Kofahi, Mohammed N Sawalhah, Ahmad E Abu Dkhineh — Thu, 26 Dec 2024 00:00:00 +0000

Grazing practices fundamentally shape plant community composition and biodiversity worldwide, more importantly in water-limited environments. This study aimed to investigate plant community composition, species distribution of occurrence and diversity indices in an arid rangeland under different grazing intensities. The quadrat method was used to select 90 × 1 m² quadrats in heavy-grazing, light-grazing and ungrazed sites. Plant species frequency, relative frequency, abundance, relative abundance and density, as well as species richness, evenness, Shannon diversity index and Simpson’s diversity index were calculated. A total of 46 plant species belonging to 17 families were recorded. The Asteraceæ family was represented with the highest frequency (28%). Overall in the study area, around 95%, 70% and 40% of recorded plant families existed in light-grazing, ungrazed and heavy-grazing sites, respectively. The species richness of identified plants in light-grazing and ungrazed sites was 300% and 200% greater, respectively, than in the heavy-grazing sites. Around 85% of existing plants in heavy-grazing sites were therophyte plants. The species frequency, abundance, density and diversity indices were higher in light-grazing sites compared to those under heavy grazing, which indicates a more diverse, heterogenous and balanced plant community in the light-grazing site. Plant communities in light-grazing and ungrazed sites were similar, except for higher species frequency, density and evenness in light-grazing sites. This suggests that light-grazing intensities in the arid rangelands of Jordan enhance plant diversity more than grazing exclusion, which encourages decision-m

Assessment of the impact of woody species encroachment on plant species diversity and the livelihood of pastoralists in southeastern Ethiopia

Abdulhakim Mahmud , Habte Telila1, Lemessa Kumsa — Thu, 26 Dec 2024 00:00:00 +0000

The study aimed to assess the encroachment of woody plants on the rangelands of the Dallo Manna district of Bale Zone, and their impact on plant species diversity and pastoral livelihoods. Plant data were collected from 45 plots at encroaching sites and 4 plots at non-encroached sites, with a size of 20 m × 20 m for comparison. Data on pastoral perceptions were collected through questionnaires, interviews with key informants, and focus group discussions. A total of 62 woody species were recorded at both non-encroached and encroached sites, of which 58 species (93.5%) were recorded at non-encroached sites and 24 (38.7%) at encroached sites. Dichrostachys cinerea (L.) Wight and Arn. was the most abundant and dominant invasive woody species, followed by Senegalia mellifera (Vahl) Siegler and Ebinger, and Dalbergia microphylla Chiov. Overall, our results indicated that the effects of woody species encroachment significantly affected rangeland vegetation conditions and livelihoods. The major drivers for the encroachment were found to be fire suppression, overgrazing, and dispersal syndromes. However, in order to understand the exact causes of the woody plant encroachment, multiple variables should be considered in future research. For the successful control of encroachment, insights from an integrated approach will benefit from both local traditional and scientific knowledge of the ecology.

Nutritional improvement of cactus fruit scraps with addition of alfalfa or Atriplex halimus, and comparison of two animal feed preservation methods (silage and solar drying)

L El Hajji, H Azzouzi, M Achchoub, K Elfazazi, S Salmaoui — Thu, 26 Dec 2024 00:00:00 +0000

This work aimed to study the effect of adding alfalfa (Medicago sativa L.) and Atriplex halimus L. on biochemical properties, microbial flora, ferment silage and solar-dried cactus fruit scraps. Alfalfa and Atriplex were added to cactus silage to improve nutrient quality. Three mixtures were prepared: M1 based on cactus, M2 based on cactus and alfalfa, and M3 based on cactus and Atriplex. Bran and wheat straw were added to the mixtures to improve the moisture content. After adding alfalfa and Atriplex, the protein content of the pre-ensiling material increased (p < 0.05), reaching 10.63% DM for M1, 16.35% DM for M2, and 17.22% DM for M3. During ensilage, a significant amount of sugar and protein was degraded. All silage treatments achieved stable pH values (M1: 4.35, M2: 4.55, and M3: 4.54). The M2 and M3 treatments had the highest amount of protein. After drying, the protein content of the dried treatments was higher than that of the ensiled treatments (8.05% DM for M1, 14.96% DM for M2, and 15.36% DM for M3). In both storage methods, the microbial population declined. However, silage reduces coliforms, yeasts and moulds more efficiently than solar drying. The drying operation preserves remarkedly the nutritional quality of the mixtures while ensiling reduces the number of undesirable microorganisms.

Fire suppression interacts with soil acidity to maintain stable recalcitrant pyrogenic carbon fractions in South African mesic grasslands soil

Robyn E Nicolay, Ntuthuko R Mkhize, Michelle J Tedder, Kevin P Kirkman — Thu, 26 Dec 2024 00:00:00 +0000

Grassland ecosystems have evolved alongside fire, a fundamental element that shapes and sustains their ecological balance. Recent research indicates that carbon produced during pyrogenic events in fire-dependent ecosystems may occur in more recalcitrant forms within deeper soil horizons. Notably, refractory organic carbon (ROC) and black carbon (BC) fractions are globally recognised as highly stable components of soil carbon. Here, we examined the impact of prescribed fires on the accumulation of ROC and BC fractions within South African mesic grassland soils. Our findings revealed that while BC remains stable in the soil, exhibiting consistent levels across soil horizons, increased fire frequency led to breakdown of BC in the soil. Greater BC quantities were observed in burn exclusion and prescribed burns with a greater burn interval, suggested as primarily driven by a decline in soil pH. There were no significant differences in ROC within the burn treatments, but there was a notable decrease in ROC with increasing depth increments below 5 cm. The observed trend of ROC accumulation in the top layer of soil, influenced by increased prescribed fire frequency, may contribute to the post-fire recovery and resilience of fire-adapted ecosystems.

Influence of different temperatures on seedling growth and development of Calobota sericea, a semi-arid rangeland species of South Africa

Francuois Müller, Letty Masemola, Fortune Manganyi , Nothando Ngcobo — Thu, 26 Dec 2024 00:00:00 +0000

This study determined how temperature affected the early growth of seedlings of Calobota sericea (Thunb.) Boatwr. & B.-E.van Wyk. One-month-old C. sericea seedlings were grown at constant temperatures of 2.5, 5, 10 and 20 °C for 30 days. After 30 days the plants were removed and shoot length, root length, stem thickness, number of leaves, middle leaflet length, leaf width, petiole length, shoot fresh and dry mass, and cell membrane stability through electrolyte leakage from the leaves, and shoot water content were measured. Results showed that the optimum temperature for C. sericea seedling growth was approximately 10 °C. Significant seedling mortality was observed at 20 °C, while no mortality was observed between 2.5 and 5 °C, and less than 4% of seedlings died at 10 °C. The majority of measured morphological variables in this study increased significantly from 2.5 °C and 5 °C, reaching a maximum at 10 °C before decreasing significantly at 20 °C. Electrolyte leakage from leaves was significantly more at 2.5 °C and at 20 °C, suggesting that seedlings were more stressed at these temperatures. In conclusion, even though C. sericea has a wide optimum germination temperature range, early seedling growth requires a narrow temperature range for optimum growth and development.

‘The Fluvial Imagination: On Lesotho’s Water-Export Economy'

Adrian Nel — Thu, 26 Dec 2024 00:00:00 +0000

No abstract.

‘Fairy Circles of the Namib Desert: Ecosystem Engineering by Subterranean Social Insects’

David Ward — Thu, 26 Dec 2024 00:00:00 +0000

No abstract.

‘Sustainability of Southern African Ecosystems under Global Change’

Brian W van Wilgen — Thu, 26 Dec 2024 00:00:00 +0000

No abstract.

‘The African Baobab’

Sarah M Venter — Thu, 26 Dec 2024 00:00:00 +0000

No abstract.