7 research outputs found
Improving Grassland Quality in Communal Arable Lands in the Eastern Cape Province, South Africa
Overgrazing and shifting cultivation practise have severely degraded communal lands in the Eastern Cape of South Africa. Methods need to be developed to improve forage quality of grazing land, especially previously cultivated lands. The aim of the study was to investigate legume species to rehabilitate arable lands abandoned from cropping, to enhance their forage quality, productivity and ecological integrity. The study was conducted in seven communities within the Eastern Cape Province. This study showed that within the communal lands studied extensive areas have been cultivated and the majority of this land is now poorly utilised. Natural grasslands ploughed for cropping did not recover its original composition and therefore lost its primary ecological condition. New improved legume cultivars can significantly enhance forage quality on cultivated lands but individual species may not have the resilience to survive nutrient poor lands and variable winter rainfall. This study shows that using a mixture of annual and perennial legume species with different life traits contributed to enhanced forage quality, especially during winter when the nutritional value of grasses was low. Because of management constraints, pasture legumes cannot be seen as stand-alone pastures, but provide a mechanism to extend the forage potential of communal grazing lands
Using Sentinel-1 and Sentinel-2 Time Series for Slangbos Encroachment Mapping in the Free State Province, South Africa
Increasing woody cover and overgrazing in semi arid ecosystems are known to be major factors driving land degradation. During the last decades woody cover encroachment has increased over large areas in southern Africa inducing environmental, land cover as well as land use changes.
The goal of this study is to synergistically combine SAR (Sentinel 1) and optical (Sentinel 2) earth observation information to monitor the slangbos encroachment on arable land in the Free State province, South Africa, between 2015 and 2020. Both, optical and radar satellite data are sensitive to different land surface and vegetation properties caused by sensor specific scattering or reflection mechanisms they rely on.
This study focuses on mapping the slangbos aka bankrupt bush (Seriphium plumosum) encroachment in a selected test region in the Free State province of South Africa. Though being indigenous to South Africa, the slangbos has been documented to be the main encroacher on the grassvelds (South African grassland biomes) and thrive in poorly maintained cultivated lands. The shrub reaches a height and diameter of up to 0.6 m and the root system reaches a depth of up to 1.8 m. Slangbos has small light green leaves unpalatable to grazers due to their high oil content and is better adapted to long dry periods compared to grass communities.
We used the random forest approach to predict slangbos encroachment for each individual crop year between 2015 and 2020. Training data were based on expert knowledge and field information from the Department of Agriculture, Forestry and Fisheries (DAFF). Several input variables have been tested according to their model performance, e.g. backscatter, backscatter ratio, interferometric coherence as well as optical indices (e.g. NDVI (Normalized Difference Vegetation Index), SAVI (Soil Adjusted Vegetation Index), EVI (Enhanced Vegetation Index), etc.). We found that the Sentine 1 VH backscatter (vertical horizontal/cross polarization) and the Sentinel 2 SAVI time series information have the highest importance for the random forest classifier among all input parameters. The estimation of the model accuracy was accomplished via spatial cross validation and resulted in an overall accuracy of above 80 % for each time step, with the slangbos class being close to or above 90 %.
Currently we are developing a prototype application to be tested in cooperation with local stakeholders to bring this approach to the farmers level. Once field work in southern Africa is possible again, further ground truthing and interaction with farmers will be carried out
Earth Observation Strategies For Degradation Monitoring In South Africa With The Sentinels - Results From The Spaces II Saldi-Project
The overarching goal of SALDi (South African Land Degradation MonItor) is to implement novel, adaptive, and sustainable tools for assessing land degradation in multi-use landscapes in South Africa. This presentationdemonstrates results from hyper-temporal Sentinel-1 and -2 timeseries concerning woody cover mapping in complex savanna systems, invasive slangbos bushencroachment in grassland areas and regional soil moisture retrievals. Validation has been performed by cross-comparisons, field trips and permanently installed soil moisture networks
The assessment of topsoil degradation on rehabilitated coal discard dumps
Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2004.This study investigates coal discard cover soil fertility and its potential for
degradation, particularly in terms of its salinisation and acidification potential. Seven
rehabilitated coal discard dumps in the Witbank, Ermelo and Newcastle regions were
used as study areas. All areas were rehabilitated with a cover soil layer, revegetated
and annually fertilised with nitrate fertilisers, super phosphate, kraal manure and
lime. Performance guideline for pH of 5.5-(6.5 i0.5)-7.5 and electrical conductivity
guideline of preferably less than 200 mS.rn-' but not higher than 400 mS.m-' were set
based on literature information. Soil chemical data from a three-year fertilisation
programme were used to assess the fertility of the cover soil surface (0-150mm).
Data collected over a three year period as well as additional electrical conductivity
and pH measurements from the cover soil surface, subsoil, cover soil/coal contact
zone and underlying coal itself were used to assess the occurrence of salinisation
and acidification of the cover soil. The soil fertility varied significantly among dumps
as well as over the three years. Results indicated an increase in ammonium acetate
extractable macro elements (calcium, magnesium and potassium). With the
exception of manganese, no micro-element toxicities were recorded. Iron
concentrations were slightly elevated in some of the sandy cover soil layers. No
increase in soluble nitrogen (nitrate and ammonium) was found and most soluble
nitrogen was in the form of nitrates. In general the Bray extractable phosphate
increased during the study period. It can be predicted that with the following fertiliser
programme increases of exchangeable macro-elements as well as available
phosphorus can be expected. The study could not indicate an increase in adsorbed
or available nitrogen. Organic carbon was initially not analysed therefore no
comments can be made whether organic matter increased. Four of the seven dumps
surveyed had comparably similar organic carbon levels to the background samples.
Overall the fertiliser programme increased the electrical conductivity and decreased
the acidity of the cover soil surface. Acidity and salinity was in general not a problem
at the surface of the cover soil and pH was even slightly higher in cover soil samples.
The acidity and especially salinity increased at the subsoil and so did the sulphate
concentrations. Calcium and magnesium sulphate were predominantly responsible
for higher electrical conductivity measurements. The percentage exchangeable
sodium was also predominantly less than 2% indicating that sodicity is not currently a
problem in cover soil. Soil fertility was satisfactory for vegetation growth and macroelement
concentrations were in the correct ratio although calcium was slightly high.
An elevated sulphate concentration, in comparison to the natural grassland soils, as
well as a high salinity and high acidity in the subsoil layers indicate that salinisation
and acidification could deteriorate without proper management. A slightly acidic
cover soil can also be attributed partially to its natural acidic pH due to the wellweathered
and leach property of burrow pit. Higher than recommended salinity
levels were found in subsoil samples but the occurrence of acidification of the subsoil
was more dump specific. In relation to acidity and salinity guidelines only the cover
soil of one dump was concerning and the larger dumps subsoil acidity and salinity
were elevated.
The following management strategies are proposed:
a) The acidification potential, and therefore the pyrite content of the coal discard
must be considered during decisions making on the rehabilitation method
(clay barriers), topsoil depth, maintenance and mine closure potential.
b) The occasional monitoring of the subsoil's and coal contact acidity is
recommended, although not much can be done to stop acidification after
cover-soil placement.
c) To ensure a more sustained from of nitrogen supplementation over the long
term the use of selected legumes should be investigated. Research in
Europe and Australia suggested that nitrogen fixation could contribute
substantially to the nitrogen for plant uptake.
d) The physical properties of the topsoil (bulk density 8 soil compaction) are also
being neglected and needs to be assessed occasionally and interpreted
together with chemical analyses. Observations in other studies indicate that
this could be the most fundamental problem for vegetation growth and not
necessarily soil fertility, since soil physical properties could have a major
impact on root development.
Key words: Coal discard, mine rehabilitation, soil fertility, topsoil degradation,
salinisation, and acidificationMaster
Sentinel-1 and Sentinel-2 Time Series Breakpoint Detection as Part of the South African Land Degradation Monitor (SALDi)
Earth Observation Strategies For Degradation Monitoring In South Africa With The Sentinels - Results From The Spaces II Saldi-Project
The overarching goal of SALDi (South African Land Degradation MonItor) is to implement novel, adaptive, and sustainable tools for assessing land degradation in multi-use landscapes in South Africa. This presentationdemonstrates results from hyper-temporal Sentinel-1 and -2 timeseries concerning woody cover mapping in complex savanna systems, invasive slangbos bushencroachment in grassland areas and regional soil moisture retrievals. Validation has been performed by cross-comparisons, field trips and permanently installed soil moisture networks
Earth Observation Strategies For Degradation Monitoring In South Africa With The Sentinels - Results From The Spaces II Saldi-Project
The overarching goal of SALDi (South African Land Degradation MonItor) is to implement novel, adaptive, and sustainable tools for assessing land degradation in multi-use landscapes in South Africa. This presentationdemonstrates results from hyper-temporal Sentinel-1 and -2 timeseries concerning woody cover mapping in complex savanna systems, invasive slangbos bushencroachment in grassland areas and regional soil moisture retrievals. Validation has been performed by cross-comparisons, field trips and permanently installed soil moisture networks