Browsing by Author "Vetter, Susanne"

Now showing 1 - 3 of 3

Rainfall and Soils, Not Grazing Intensity, Determine the Composition and Productivity of Annual Plants in a Biodiverse Arid Winter Rainfall Region
(Journal of Natural Sciences Research, 2021-05-07) Konje, Martha Muthoni; Muoria, Paul K.; Wabuyele, Emily; Griffin, Neil; Vetter, Susanne
Concentration of grazer activity around watering points and stock posts has led to well-documented vegetation impacts in arid and semi-arid rangelands. Effect of grazing and abiotic factors on perennial plant diversity have been reported in the bio-diverse winter rainfall vegetation of the Succulent Karoo in South Africa, but the impact on annuals had not been investigated. The aim of this study was to assess the effect of rainfall, soil nutrients, land forms and grazing on forage depletion, soil chemistry and the composition, diversity, richness and biomass production of annual plants in the Richtersveld National park, which is a contractual national park used by seminomadic pastoralists to herd goats and sheep. A grazing gradient away from stock posts at 100m, 500m and 1000m on sandy plains and rocky foothills at five study sites with different mean annual rainfall and vegetation types were used. Distance from stock posts corresponded to a gradient of forage depletion and resulted in changes in soil chemistry with distance. Biomass production, richness and diversity of annuals were correlated with rainfall but not significantly affected by landform or distance from stock posts. Rainfall and soil variables had a greater influence on species composition than grazing in this arid ecosystem. The decrease in perennial cover and richness near the stock posts was not accompanied by increase in biomass production or richness of annuals, which is expected to have adverse effects on overall plant diversity and forage availability.
Spatial-temporal variation of biomass production by shrubs in the succulent karoo, South Africa
(Journal of Biodiversity and Environmental Sciences, 2021-04-30) Konje, Martha Muthoni; Muoria, Paul; Wabuyele, E.; Vetter, Susanne
Forage production in arid and semi-arid rangelands is not uniform but varies with seasons and in various landscapes. The aim of this study was to investigate the spatial and temporal variation in forage production in RNP. Plants sampling was carried out in 225 plots distributed in each of the five vegetation types. In each vegetation strata, sampling points was based on proximity to an occupied stock post, a rain gauge, a foothill and flat plains. A total of were measured in the 5 study sites. Line Intercept Method in combination with harvest method were used in ground measurement of biomass production. To assess biomass production using remote sensing technique, par values were obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) imageries which consisted of 8 days composite images at spatial resolution of 1km² pixel size. There was positive correlation between line intercepts and biomass production Biomass production was higher in succulent Karoo biome than in desert biome. There was a strong relationship between biomass production with rainfall and with fpar values. Since leaf and stem succulents’ plants were found to contribute the highest amount of forage production in RNP, they should be given conservation priority.
Spatio-Temporal Variation In Forage Production In A Key Resource Area In Succulent Karoo Rangeland, South Africa
(Researchjournali’s Journal of Ecology, 2021-03-07) Konje, Martha Muthoni; Muoria, Paul; Wabuyele, Emily; Vetter, Susanne
For herbivores to survive in arid rangelands, they largely depend on landscapes that act as grazing reserves during the dry seasons. In Richtersveld National Park, the dry season forage consists of browse from tree branches, litter and grass that grow along the Orange River. The aim of the study was to determine how browse production by tree species along the riparian zone (a key resource area), vary between the sites, with time and among the tree species, as well as the implication of a dry season key resource in management of rangelands. Sampling of tree species took place at three study sites along the riparian zone. In each site, temporal available standing biomass, browse and litter production by the seven dominant tree species were sampled. To calculate the total biomass production per tree canopy area, branch-count method was used up to a height of 1.5 m. Browse production differed between the tree species and between sampling periods but not between the sampling sites. Key resource area was found to play an important role in sustaining herbivores populations during the dry seasons as well as to reduce the negative effects associated with continuous grazing on the landscapes.