Rangeland Modelling Group
Department of Mathematics &
Applied Mathematics
University of Cape Town
Rondebosch 7701
South Africa
Staff
email: bdh@maths.uct.ac.za
telephone: +27-21-650-3191
fax:
+27-21-650-2334
email: fd.rich@mweb.co.za
telephone: +27-21-852-4833
fax:
+27-21-650-2334
email: gareth@maths.uct.ac.za
telephone: +27-21-650-3201
Objectives
- Development of mechanistic
computer-based models of semi-arid to arid rangeland systems, in
order to understand them and to re-evaluate current rangeland theories and
management practices;
- Evaluation of alternative
production strategies, as aids to short-and medium-term decision making,
and prediction of requirements for drought relief;
- Development of user-friendly
software (written in Turbo Pascal and Delphi) for use as an aid to
decision making by rangeland managers and advisors.
We have developed a suite of mechanistic production system models based on
differential equations which predict animal dry matter intake, weight gains
and milk yields on a daily basis, given rainfall (actual or simulated), soil
type, vegetation and stocking rate. Output from these production system models
are incorporated into simulations of entire rangelands over many decades using
the frame-based modelling paradigm.
Future
projects
Models developed for the following projects could form the basis of an MSc
or PhD thesis. These are multi-disciplinary projects and honours graduates in
any branch of science or agriculture will be considered. Some knowledge of
computer programming would be helpful. NRF funding is available.
Namaqualand livestock-ecosystem model
In collaboration with the National Botanical Institute and the Department
of Animal Science at the University of Fort Hare we are developing a series of
computer simulation models of livestock production and the ecosystem for
communal rangelands in Namaqualand. You will develop a computer simulation
model of diet selection and nutrient utilization by sheep and goats grazing
succulent Karoo. This is a multidisciplinary project that will involve both
some experimental work in the field and computer modelling.
Goat model
Recent results from the rangeland modelling project have indicated the
important influence of goats on the stability and sustainability of rangeland
systems. Consequently rangeland models depend on accurate representation of
the performance of goats and their impact on the vegetation and on the
productivity of the whole system. The sub-models that simulate diet selection,
nutrient utilisation, production (meat, milk, fibre), reproduction and
mortality of free ranging goats need to be further developed.
Frame-based models of the rumen
The end products of microbial fermentation in the rumen provide the major
proportion of nutrients available to the host animal. Many microbial species
are present in the rumen and most are selective fermenters. The pattern of end
products produced and rate of fermentation varies with the relative
proportions of species present and the food eaten. The rumen microbial
population varies with the diet, amount eaten and time since a specific food
was eaten. The different organisms interact with one another and with the
rumen contents. Rumen models that simulate changes in the proportions of
different microbial species are very complex even if only three types of
organism are represented. To date no model incorporates rumen anaerobic fungi
which may play important roles in the digestion of lignified rangeland plants.
There is an opportunity to develop a simple model of rumen fermentation using
frame-based modelling techniques.
Recent work
- Richardson
F D, B D Hahn and P I Wilke (1991). A model for the evaluation of
different production strategies for animal production from rangeland in
developing areas: an overview. Journal of the Grasslands Society of
Southern Africa 8, 153-159.
- Hahn
B D, F D Richardson and A M Starfield (1998). A frame-based model for
rangeland production systems. BSAS/KARI Proceedings of an International
Conference on Food, Lands and Livelihoods: Setting Research Agendas for
Animal Science (Nairobi, January 27-30). Edinburgh. 99-100.
- Richardson
F D, B D Hahn and S J Schoeman (1998). Simulation models of rangeland
production systems for developing areas. BSAS/KARI Proceedings
of an International Conference on Food, Lands and Livelihoods: Setting
Research Agendas for Animal Science (Nairobi, January 27-30).
Edinburgh. 16-17.
- Richardson,
F D and G Q Witten (1998). A simulation model of the short- and long-term
effects of undernutrition on body weight and composition of growing
cattle. BSAS/KARI Proceedings of an International Conference on Food,
Lands and Livelihoods: Setting Research Agendas for Animal Science (Nairobi,
January 27-30). Edinburgh. 101-102.
- Hahn
B D, F D Richardson and A M Starfield (1998). A simple frame-based model
of a complex rangeland system. Proceedings of the 36th National
Congress of SASAS: Animal Production in Harmony with the Environment (Stellenbosch,
April 5-8). 225-226.
- Richardson
F D, B D Hahn and S J Schoeman (1998). Simulation models for managing
rangeland systems. Proceedings of the 36th National Congress of SASAS:
Animal Production in Harmony with the Environment (Stellenbosch, April
5-8). 223-224.
- Richardson,
F D and G Q Witten (1998). A simulation model of the short- and long-term
effects of undernutrition on body weight and composition of growing
cattle: model development and sensitivity analysis. Proceedings of the
36th National Congress of SASAS: Animal Production in Harmony with the
Environment (Stellenbosch, April 5-8). 227-228.
- Hahn
B D, F D Richardson and A M Starfield (1998). Frame-based models as tools
for evaluating rangeland management strategies. Communal Rangelands in
Southern Africa: A synthesis of knowledge (Grasslands Society of SA,
Fort Hare, July 6-9). 269-273.
- Richardson
F D, B D Hahn and S J Schoeman (1998). The role of simulation models in
understanding communal rangeland systems in Southern Africa. Communal
Rangelands in Southern Africa: A synthesis of knowledge (Grasslands
Society of SA, Fort Hare, July 6-9).119-123.
- Hahn
B D, F D Richardson and A M Starfield (1999). Frame-based
modelling as a method of simulating rangeland production systems in the
long term. Agricultural Systems 62, 29-49.
- Hahn
B D, S Todd, P Carrick, T Hoffmann, F D Richardson and R Roberts (1999). A
frame-based model of plant, climate and animal interactions in a communal
area of Namaqualand. Arid Zone Ecology Forum (Vanrhynsdorp,
September 6-8).
- Richardson
F D, B D Hahn and M T Hoffman (1999). Simulation models of Namaqualand
pastoral systems: simple and complex. Arid Zone Ecology Forum (Vanrhynsdorp,
September 6-8).
- Richardson
F D, B D Hahn and S J Schoeman (2000). Modelling nutrient utilization by
livestock grazing semi-arid rangeland. In Modelling Nutrient
Utilization in Farm Animals, ed. J P McNamara, J France and D Beever,
CABI Publishing, Wallingford UK and New York, 263-280.
- Witten
G Q and F D Richardson (2000). Modelling nutrient utilization in growing
cattle subjected to short or long periods of moderate to severe
undernutrition. In Modelling Nutrient Utilization in Farm Animals,
ed. J P McNamara, J France and D Beever, CABI Publishing, Wallingford UK
and New York, 241-252.
- Witten
G Q and F D Richardson (2000). Dynamic control of ammonia and urea
diffusion across the rumen wall. Mathematical Modeling in Nutrition and
the Health Sciences (Penn State University, USA, July 29 - August 1).
- Witten
G Q (2000). Modelling the control of energy partitioning between protein
and fat during undernutrition. International Conference on Mathematical
Biology (University of Utah, USA, August 3-5).
- Richardson
F D, B D Hahn, M T Hoffman and R Roberts (2001). Simulation models of a
Namaqualand pastoral production system. Grasslands Society of Southern
Africa (Aventura Aldam, Free State, January).
- Witten
G Q and F D Richardson (2001). Competition of three aggregated microbial
species for complementary substrates in the rumen. South African
Society for Numerical and Applied Mathematics (Stellenbosch, April
9-11).
- Hahn
B D, F D Richardson, M T Hoffman, R Roberts, S W Todd and P Carrick
(2001). An overview of a simulation model of long-term climate, livestock
and vegetation interactions and sustainability on communal rangelands in
the semi-arid Succulent Karoo, Namaqualand. Arid Zone Ecology Forum
(Calitzdorp, September 5-7).
- Richardson
F D, B D Hahn and M T Hoffman (2001). Modelling the influences of
rangeland degradation, rainfall and management on livestock productivity
in Namaqualand. Arid Zone Ecology Forum (Calitzdorp, September
5-7).
- Witten
G Q and F D Richardson (2001). Managing arid and semi-arid rangelands
accounting for the variability of key factors over space and time. Arid
Zone Ecology Forum (Calitzdorp, September 5-7).
- Richardson
F D, B D Hahn and M T Hoffman (2001). Modelling sheep and goat production
in a communal area of Namaqualand. Developing Areas Interest Group of
the South African Society of Animal Science (Nooitgedacht, Ermelo, 30
October 30-November 1)
- Witten G Q and F D Richardson
(2002). Competition of three aggregated microbial species for four
substrates in the rumen. Ecological Modelling (in press)
- Witten
G Q and F D Richardson (2002). Modelling rumen function: the effects of
different N supplements on low quality roughages. Journal of
Agricultural Science (submitted)
- Richardson F D, B D Hahn and M T Hoffman(2002).
Instability leads to sustainability in a Namaqualand pastoral system.
Third Biomathematics Symposium (University of Cape Town, February 8).
- Richardson
F D, B D Hahn and S J Schoeman (2002). Modelling milk production in
suckling ruminants: driven by potential and demand, but limited by
nutrient supply. South African Society for Numerical and Applied
Mathematics (Stellenbosch, April 3-5).
- Chawatama S, L R Ndlovu, F D
Richardson, F Mhlanga and K Dzama (2003). A simulation model of draught
animal power in smallholder farming systems. Part I: Context and
structural overview. Agricultural Systems 76, 415-440.
- Chawatama
S, L R Ndlovu, F D Richardson, F Mhlanga and K Dzama (2003). A simulation
model of draught animal power in smallholder farming systems. Part II:
Model evaluation and application. Agricultural Systems 76,
441-455.
- Richardson F D, B D Hahn and M T Hoffman(2003).
Understanding arid and semi-arid grazing systems: why both equilibrium and
non-equilibrium concepts are inadequate. Fourth Biomathematics Symposium
(University of Cape Town, February 6-7).
- Hahn
B D, F D Richardson and M T Hoffman (2003). A simulation model of
long-term climate, livestock and vegetation interactions on communal
rangelands in the semi-arid Succulent Karoo, Namaqualand, South Africa.
Fourth Biomathematics Symposium (University of Cape Town, February 6-7).
- Hahn
B D, F D Richardson and M T Hoffman (2003). On the dynamic behaviour of
grazing systems. South African Society for Numerical and Applied
Mathematics (Stellenbosch, March 31–April 2).
- Richardson
F D, B D Hahn and M T Hoffman (2003). Modelling the dynamics of a
Namaqualand pastoral system. Proceedings of the VIIth International
Rangeland Congress (Durban, July 26–August 1), African Journal of
Range & Forage Science 20(2):142.
- Richardson
F D, B D Hahn and M T Hoffman (2003). The dynamics of arid and
semi-arid grazing systems. Professional workshop 01: Rangelands in
equilibrium and disequilibrium, pp.38–54. VII International Rangeland
Congress, Durban, 25–26 July.
- Richardson
F D, B D Hahn and M T Hoffman (2004). Understanding arid and
semi-arid grazing systems: why both equilibrium and non-equilibrium
concepts are inadequate. In:
S. Vetter (Editor), Rangelands at equilibrium and non-equilibrium,
Programme for Land and Agrarian Studies, School of Government, University
of the Western Cape, Cape Town, pp. 17–29.
- Hahn
B D, F D Richardson and M T Hoffman (2004). Modelling the impact of
management interventions and climatic change on rangeland condition and
livestock production on communal rangelands in the semi-arid Succulent
Karoo. Arid Zone Ecology Forum (Victoria West, 30 August – 2 September).
- Richardson
F D (2004). Simulation models of rangeland production systems: simple and
complex. PhD thesis, University of Cape Town (unpublished).
- Hahn
B D, F D Richardson, M T Hoffman, R Roberts, S W Todd and P Carrick
(2005). A simulation model of long-term climate, livestock and vegetation
interactions on communal rangelands in the semi-arid Succulent Karoo,
Namaqualand, South Africa. Ecological Modelling (in press).
- Richardson
F D, B D Hahn and M T Hoffman (2005). On the dynamics of grazing systems
in the semi-arid succulent Karoo: the relevance of equilibrium and
non-equilibrium concepts to the sustainability of semi-arid pastoral
systems. Ecological
Modelling (accepted).
- Richardson
F D and B D Hahn (2005). A mechanistic model of semi-arid rangeland to
simulate within years the effects of rainfall, stocking rate and range
condition on the productivity of forage and livestock: 1. Overview of the
model and description of the sub-models of
soil moisture, plant growth, diet selection and food intake by goats and
cattle on arid shrubland and savanna. Agricultural Systems
(submitted).
- Richardson
F D and B D Hahn (2005). A mechanistic model of semi-arid rangeland to
simulate within years the effects of rainfall, stocking rate and range
condition on the productivity of forage and livestock: 2. Description of
the sub-models of utilisation of dietary energy by, and reproduction and
survival of, goats and cattle on arid shrubland and savanna. Agricultural
Systems (submitted).
- Richardson
F D and B D Hahn (2005). A mechanistic model of semi-arid rangeland to
simulate within years the effects of rainfall, stocking rate and range
condition on the productivity of forage and livestock: 3. Implementation,
evaluation and application. Agricultural Systems
(submitted).
Last updated: 20 January 2005 by Brian
Hahn
Speciality:development of hands-on
modules and books to teach programming languages to beginners: Fortran,
GWBASIC, Pascal, True BASIC, C, C++, Matlab, Java
