Carbon and nitrogen system dynamics in three small South African estuaries, with particular emphasis on the influence of seasons, river flow and mouth state

2016 ◽  
Vol 557 ◽  
pp. 17-30 ◽  
Author(s):  
K Ortega-Cisneros ◽  
UM Scharler ◽  
AK Whitfield
Keyword(s):  
System Dynamics ◽  
South African ◽  
River Flow ◽  
Carbon And Nitrogen

River flow, zooplankton and dominant zooplanktivorous fish dynamics in a warm-temperate South African estuary

2018 ◽  
Vol 92 (6) ◽  
pp. 1747-1767 ◽  
Author(s):  
N. Mbandzi ◽  
R. J. Wasserman ◽  
S. H. P. Deyzel ◽  
N. G. Vine ◽  
A. K. Whitfield
Keyword(s):  
South African ◽  
River Flow ◽  
Zooplanktivorous Fish ◽  
Warm Temperate

MODELING EFFECTS OF INCENTIVES FOR INDUSTRY COMPETITIVENESS USING A SYSTEM DYNAMICS APPROACH

2012 ◽  
Vol 09 (02) ◽  
pp. 1250011
Author(s):  
MARTIN KAGGWA ◽  
JASPER L. STEYN ◽  
ANASTASSIOS POURIS
Keyword(s):  
System Dynamics ◽  
South African ◽  
Manufacturing Sector ◽  
Quantitative Information ◽  
Policy Framework ◽  
Automotive Manufacturing ◽  
Industry Competitiveness ◽  
Policy Lever ◽  
Industry Investment

Investment in state of the art machinery and tooling and in R&D is widely seen as a prerequisite for achieving industry competitiveness in the long term. Investment-based incentives that countries provide for these inputs are perceived as a way of supporting industry competitiveness. Despite this being a global phenomenon, there is no formal process to guide the offer of these incentives. The process of designing such incentives is often based on internalized judgment rather than on formal models making it difficult to assess such interventions objectively and to improve on them. Specific to South Africa, the offer of incentives to the automotive industry to support its competitiveness has had mixed results. In particular, investment in R&D has remained minimal. The paper presents a system dynamics model as a proposed instrument in formalizing the offer of incentives, applied to the South African government's offer of incentives to the automotive manufacturing sector. The model was developed from qualitative and quantitative information on how the incentives had been structured. Simulations of the model reveal that the incentives model, as a stand-alone intervention, had a significant and positive effect on industry investment, but had no specific policy lever to direct investment into R&D and subsequent innovative activities. By this measure, the incentives model has not been a strong policy framework for supporting long-term industry competitiveness.

scholarly journals Using Qualitative System Dynamics Analysis to Promote Inclusive Livestock Value Chains: A Case Study of the South African Broiler Value Chain

2021 ◽  
Vol 5 ◽  
Author(s):  
Soledad Cuevas Garcia-Dorado ◽  
Kevin Queenan ◽  
Bhavani Shankar ◽  
Barbara Häsler ◽  
Tafadzwanashe Mabhaudhi ◽  
...  
Keyword(s):  
System Dynamics ◽  
South African ◽  
Value Chain ◽  
Food Systems ◽  
Rural Livelihoods ◽  
Value Chains ◽  
Illustrative Case ◽  
The South ◽  
Entry Points

Livestock value chains globally are increasingly dualistic, with integrated market-leaders co-existing with comparatively disadvantaged small producers who, nevertheless, support rural livelihoods and food access, and can also contribute to more resilient supply chains. The South African broiler value chain provides a highly illustrative case study. The purpose of this study is to identify potential leverage points for policy intervention to support small and emerging producers in the South African broiler value chain, and to discuss the strengths and limitations of system dynamics approaches to promote inclusive food value chains. This study develops a causal loop diagram (CLD) based on semi-structured stakeholder interviews and policy documents. The main challenges, key variables and causal relationships between them are systematically identified. Variables are coded, generalised and graphically represented, and entry points for intervention and their links to existing policies are mapped. The challenges faced by smallholders in the context of our study can be characterised, using a CLD, as a set of interlinked and reinforcing dynamics which perpetuate existing disadvantages and reinforce duality in the value chain. Key policy entry points have been identified that could be targeted by a coordinated policy package, including: Direct support for infrastructure investment and input access through grants, subsidies or other policies; credit and liquidity provision for day-to-day expenses; creation of aggregation mechanisms for both inputs and outputs; regulations or initiatives that directly target the relationship of farmers with the commercial segment to improve access to day-old-chicks and, finally, training in business and technical skills. Although most of these interventions have been addressed at some point, implementation has been fragmented, failing to fully consider their complementary nature, thus undermining effectiveness. Existing approaches to consensus building and stakeholder participation in system dynamics research can present challenges when it comes to engaging with complex policy processes and issues of conflict of interest that are relevant in the context of smallholder promotion and equitable food systems, but there are promising avenues for addressing. Despite some methodological challenges, we find that there is considerable scope for system dynamics approaches to inform policy for smallholder promotion, even in contexts characterised by complex policy processes.

The carbon and nitrogen cost associated with the growth, reproductive and dormant phases of two South African semi-arid geophytic species of Gethyllis (Amaryllidaceae)

2013 ◽  
Vol 61 (7) ◽  
pp. 528 ◽  
Author(s):  
Christiaan Daniels ◽  
Wilfred Mabusela ◽  
Jeanine Marnewick ◽  
Alexander Valentine
Keyword(s):  
South African ◽  
Physiological Responses ◽  
Natural Habitat ◽  
Resource Utilisation ◽  
Growth Phases ◽  
Succulent Karoo ◽  
Reproductive Growth ◽  
Carbon And Nitrogen ◽  
Flower Production ◽  
Vegetative And Reproductive Growth

Gethyllis multifolia L.Bolus and G. villosa Thunb. (Family: Amaryllidaceae) are deciduous and bulbous geophytes that occur in the succulent Karoo biome of South Africa. Both species occupy the same natural habitat, but G. multifolia is threatened and G. villosa not. Both G. multifolia and G. villosa require seasonal bulb reserves for initial vegetative and reproductive growth. In spite of G. villosa having smaller bulbs than G. multifolia, both species produce similar flower sizes and weights. The aim of the present study was to determine the carbon and nitrogen costs of vegetative and reproductive growth during the phases of growth, senescence, reproduction and dormancy of these bulbous species. The rates, costs and efficiencies of biomass production during various growth phases of the two species were determined in a comparative experiment. The results show that in spite of a significantly smaller bulb, G. villosa produced more leaves per unit bulb mass and invested more carbon and nitrogen resources into the bulbs during senescence. G. villosa also had a higher flower production, relative to bulb weight, than did G. multifolia. These physiological responses suggest that G. villosa may be more efficient at carbon and nitrogen resource utilisation.

scholarly journals Estimated abundance and diversity of heterotrophic protists in South African biocrusts

2016 ◽  
Vol Volume 112 (Number 7/8) ◽  
Author(s):  
Kenneth Dumack ◽  
Robert Koller ◽  
Bettina Weber ◽  
Michael Bonkowski ◽  
◽  
...  
Keyword(s):  
South African ◽  
Soil Nutrient ◽  
Ecosystem Functions ◽  
Turnover Rates ◽  
Succulent Karoo ◽  
Functional Roles ◽  
Carbon And Nitrogen ◽  
Different Types ◽  
Abundance And Diversity ◽  
Soil Protists

Abstract Biological soil crusts (biocrusts) occur widely in the uppermost millimeters of the soil in arid and semi-arid systems. Worldwide they cover large terrestrial areas and play a major role in the global terrestrial carbon and nitrogen cycles. However, knowledge of the microbial decomposer foodwebs within biocrusts is particularly scarce. Heterotrophic protists in soil are predominantly bacterivores, and because of their high biomass compared with other soil fauna and fast turnover rates, protists are considered an important factor for soil nutrient cycling and energy fluxes. Thus, knowledge of their biodiversity, abundance and functional roles is important to understand soil ecosystem functions. We investigated the diversity and abundance of heterotrophic soil protists in different types of biocrusts from the Succulent Karoo, South Africa. With an overall diversity of 23 distinct morphotypes, soil protist biodiversity was shown to be high. The most abundant groups were Spumella-like chrysomonads, gliding bodonids, glissomonads and heteroloboseans. Protist abundance was highly variable among samples. The abundance and diversity did not differ significantly among different types of biocrusts, indicating that microscale differences, but not macroscopic soil crust builders (e.g. cyanobacteria, lichens and bryophytes), have a major impact on the protist community.

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