Physical Sciences and Mathematics Commons^™

Modelling The Effect Of A Variable Light Extinction Coefficient And Leaf Dispersion On Light Partitioning Between Species In A Grass-Clover Mixture, M Nassiri, A Elgersma

IGC Proceedings (1997-2023)

Light partitioning in a grass-clover mixture was studied using a general competition model. The model assumes a fixed extinction coefficient (k) and no leaf dispersion. This was compared with modelling the effect of different k of both species over height as well as the effect of type of leaf dispersion. These new assumptions led to a better estimation of the light partitioning between both species. For grass the effect of variable k and leaf dispersion was similar and in both cases the total absorbed light was lower than under default conditions. For clover the new assumptions led to a higher …

Kinetic Modelling During Soaking Of Dried Long Grain Paddy Mr297, Jhauharotul Muchlisyiyah, Rosnah Shamsudin, Roseliza Kadir Basha, Radhiah Shukri, Syahmeer How, Masmunira Rambli

ASEAN Journal on Science and Technology for Development

This study aimed to assess the soaking behaviour of MR 297 dried paddy under two conditions: room temperature and hot water soaking at 60°C. The experiment involved soaking dried MR297 paddy samples in water for 0.5 to 8 hours at room temperature and 0.5 to 5 hours for soaking at 60°C. The water absorption of MR 297 behaved differently at two different soaking conditions. The kinetic behaviour of the soaking process was also simulated using established 25 predictive models and incorporating 5 novel models presented in this work. The comparison of all prediction models involved using three statistical measures: the …

A Herbage Growth Model For Different Types Of Natural Grassland, J. Viégas, M. Duru, P. Cruz, J. P. Theau, P. Ansquer, C. Ducourtieux

IGC Proceedings (1997-2023)

The aim of this work was to extend existing growth models established for pure stands to a wide range of grassland communities. For this purpose we built a simple growth model, including sub-models for radiation interception and use. Parameters for the effect of nutrient rates (N, P) and defoliation regimes were based on a plant trait database. Senescence and reproductive processes were particularly considered because of their importance in late spring growth. The model makes it possible to simulate the daily biomass production as a function of both environmental factors and the functional type of the dominant species in the …

Modelling Winter Grass Growth And Senescence, D. Hennessy, S. Laidlaw, M. O'Donovan, P. French

IGC Proceedings (1997-2023)

In temperate climates, because net grass growth in winter is low, most grass growth models deal with the main growing season (Mar-Oct in the N Hemisphere), with little emphasis on grass growth in winter (Nov-Feb). However, grass tissue turns over continuously (Hennessy et al., 2004) and the fate of herbage entering the winter is important in extended grazing season systems. This study aimed to model winter grass growth for the period 15 Oct 2001 to 28 Jan 2002 for a range of autumn closing dates (1 Sep, 20 Sep and 10 Oct) by modifying an existing model, so that …

Software Ppbb_Mx: Potential Productivity Modelling Of Brachiaria Brizantha (Cultivars Marandu And Xaraés), E. R. Detomini, D. Dourado Neto

IGC Proceedings (1997-2023)

Recent improvements in computer capacity and technology allow models to be built to simulate the attributes of many agricultural processes and systems. Although Brachiaria brizantha is the most cultivated tropical grass species in Brazil, there is no single tool to predict its production under optimal conditions. The objective of this paper is to present PPBB_MX software to calibrate and simulate (using a stochastical procedure) the shoot and total biomass potential productivity (output variables) of Brachiaria brizantha as a function of the following input variables: local latitude, season (from cutting date - Julian day), length of regrowth (time, days) and climate …

Potential Climate Change Impacts On Beef Production Systems In Australia, David H. Cobon, K. L. Bell, G. M. Mckeon, J. F. Clewett, S. Crimp

IGC Proceedings (1997-2023)

There is increasing evidence suggesting that Australia's climate is changing due to enhanced levels of greenhouse gases and that it will continue to change (Pittock 2003). Climate changes are partly established, however the impact on systems, industries and process are unclear. Industry distribution reflects climatically imposed boundaries and the relative profitability of alternative land use. Climate change may negatively impact some existing industries but create opportunities for others. This study provides an assessment of the likely impacts of plausible climate change on the beef industry in central Queensland.

Yield Progress Of Perennial Ryegrass And Silage Maize - Genetic Gain Or Climate Change?, Antje Herrmann, A. Kornher, Friedhelm Taube

IGC Proceedings (1997-2023)

Gains in annual dry matter yield (DMY) from breeding achieved during the last decades are reported to range between 2.5 and 6% per decade for perennial ryegrass (Wilkins & Humphreys, 2003). In contrast, accelerated progress in improving DMY has been achieved for silage maize, varying between 8 and 13% per decade (Lauer et al., 2001). These gains are mainly attributed to (i) genetic yield potential increase, (ii) improved crop management and (iii) increased stress tolerance. The potential impact of climate change on yield progress, however, is disregarded in most studies. The objective of this study therefore was to quantify …

Seasonal Variation Of Taproot Biomass And N Content Of Lucerne Crops Under Contrasting Grazing Frequencies, E. I. Teixeira, D. J. Moot, H. E. Brown, M. Mickelbart

IGC Proceedings (1997-2023)

Taproot nitrogen reserves (TN, kg N/ha) a function of N concentration within taproots (N%) and taproot biomass (TBM) are a major determinant of lucerne (Medicago sativa L.) growth rates after defoliation and in early-spring (Avice et al., 1997b). Several studies have shown that N% changes with seasons (Cunninghan & Volenec, 1998) and defoliation frequencies (Avice et al., 1997a). However the seasonal pattern of TBM deserves further investigation as the dynamics of root reserves is a weak point in lucerne simulation models (Confalonieri & Bechini, 2004). The objective of this experiment was to assess the seasonal variation in …

Alternative Feedbase Systems For Southern Australia Dairy Farms. 3. Economic Returns From Extra Dry Matter Consumption, D. F. Chapman, S. Kenny

IGC Proceedings (1997-2023)

Growth rates of the 'traditional' perennial ryegrass pasture frequently fail to meet the seasonal feed requirements of herds in non-irrigated dairy systems in southern Australia, leading to a dependence upon additional feed at these times of the year. Farmers commonly purchase this feed off-farm, which can be costly. Growing extra feed on-farm may be more cost effective but will require additional inputs such as N fertiliser and alternative pastures/crops. The gross return to dairy farms of growing extra feed at certain times of the year can be estimated by connecting biophysical models of pasture growth to farm systems models and …

Alternative Feedbase Systems For Southern Australia Dairy Farms. 2. Seasonal Variability, S. Kenny, D. F. Chapman, D. Beca

IGC Proceedings (1997-2023)

The standard feedbase on non-irrigated dairy farms in southern Australia is perennial ryegrass- dominant pasture supplemented by concentrate feeds, silage and hay to fill seasonal feed gaps. Using models, Chapman et al. (2005) concluded that dairy producers in this region can increase forage consumption and operating profit through the use of summer-active pastures and double-cropping (winter cereal grown for silage, followed by a summer grazing crop). However, these results were based on long-term average pasture and crop growth rates and therefore do not account for seasonal variability associated with climatic variation, which is important in southern Australia. This paper …

Alternative Feedbase Systems For Southern Australia Dairy Farms: 1. Predicted Pasture/Crop Consumption And Farm Financial Performance, D. F. Chapman, S. Kenny, D. Beca

IGC Proceedings (1997-2023)

Traditional perennial ryegrass-based pastures have significant limitations for efficient feeding of dairy cattle in dryland dairy regions of southern Australia. These include strong seasonality of growth, with 50 - 60% of total annual dry matter arriving in spring and little or no growth during summer. There is clear potential for improving total forage production and the seasonality of forage supply in these regions through the use of alternative pastures (Nie et al. 2004) and fodder crops. This series of papers applies a modelling approach to investigate the potential improvements in farm productivity and profitability resulting from their use.

Modelling Of Nitrogen Allocation And Partitioning Within Lucerne (Medicago Sativa) Shoot Tissues During Recovery From Defoliation: An Approach To Estimate Forage Production And Nitrogen Composition, F. Meuriot, A. Escobar-Gutiérrez, J-C. Avice, J-C. Simon, F. Lesuffleur, F. Gastal

IGC Proceedings (1997-2023)

Lucerne has been grown over centuries for forage. Its forage production is strongly correlated to the initial taproot and stubble N reserves (Avice et al., 1996; Meuriot et al., 2004). However, the influence of cutting management on the level of N storage and the contribution of these N reserves to forage production still remain unclear and need to be studied at the whole plant level. For this purpose, a deterministic model of N allocation within the different organs and partitioning within different biochemical N pools was developed for lucerne with high and low initial N status and cutting …

Challenges In Modelling Live-Weight Change In Grazed Pastures In The Australian Subtropics, C. K. Mcdonald, A. J. Ash

IGC Proceedings (1997-2023)

In sub-tropical regions there is enormous seasonal, annual and spatial variation in pasture quality and considerable variation in quality between pasture species. The heterogeneous structure of sub-tropical pasture swards means that process based modelling of liveweight change (LWC) is particularly difficult. In response to this complexity LWC has been expressed as a function of the length of the growing season and/or pasture utilization (McKeon et al. 2000), green leaf availability, or pasture availability and climate (Hirata et al. 1993). However, these relationships vary from year to year, often fail when species composition changes, and generally explain

An Ecosystem Modelling Approach To Rehabilitating Semi-Desert Rangelands Of North Horr, Kenya, G. A. Olukoye, W. N. Wamicha, J. I. Kinyamario

IGC Proceedings (1997-2023)

Decreased rainfall, recurrent droughts and increased anthropogenic activities have led to a dramatic increase in wind erosion on pastoral lands of North Horr resulting in the reactivation of the once-stable sand dunes. This has degraded the vegetation and impoverished the local community. Mobile sand has a severe impact on dry season grazing areas (Omar & Abdal, 1994) and, therefore, affects pastoral livestock production. In North Horr, Suaeda monoica is important in camel production and for stabilising sand dunes but it has been over-utilized over the years. The objective of this study was to use ecosystem modelling approaches to examine the …

Modelling Winter Grass Growth And Senescence, D. Hennessy, S. Laidlaw, M. O'Donovan, P. French

IGC Proceedings (1997-2023)

In temperate climates, because net grass growth in winter is low, most grass growth models deal with the main growing season (Mar-Oct in the N Hemisphere), with little emphasis on grass growth in winter (Nov-Feb). However, grass tissue turns over continuously (Hennessy et al., 2004) and the fate of herbage entering the winter is important in extended grazing season systems. This study aimed to model winter grass growth for the period 15 Oct 2001 to 28 Jan 2002 for a range of autumn closing dates (1 Sep, 20 Sep and 10 Oct) by modifying an existing model, so that …

Visual Modelling Of Alfalfa Growth And Persistence Under Grazing, S. R. Smith Jr., L. Muendermann, A. Singh

IGC Proceedings (1997-2023)

A ‘virtual’ alfalfa plant model was developed at the University of Manitoba in Canada as part of a comprehensive grazing research project. This model shows an alfalfa plant ‘growing’ on a computer screen and the plant’s response to grazing (similar to time-lapse photography). The original model was constructed by Singh (2005) to show the research potential of visually modelling alfalfa plant growth. The ability to visually ‘grow’ a plant on a computer screen also offers tremendous opportunities for teaching and extension. Detailed morphological measurements were used in the construction of Singh’s model, based on single plants subjected to the following …

Autumn Root Reserves Of Lucerne Affected Shoot Yields During The Following Spring, D. J. Moot, E. I. Teixeira

IGC Proceedings (1997-2023)

Frequent grazing affects shoot yield of lucerne (Medicago sativa L.) by limiting radiation interception (Teixeira et al., 2005b) and the accumulation of endogenous reserves (C and N) in perennial storage organs like crowns and taproots (Teixeira et al., 2005a). In temperate regions, the impact of low level of perennial reserves is particularly evident during early-spring, when lucerne regrowth resumes after an overwintering period. The analysis of lucerne yield can be fragmented into its yield components of plant population, shoots per plant and yield per shoot (Volenec et al., 1987). The objective of this research was to quantify …

Lucerne Crown And Taproot Biomass Affected Early-Spring Canopy Expansion, E. I. Teixeira, D. J. Moot, A. L. Fletcher

IGC Proceedings (1997-2023)

Leaf area index (LAI) quantifies canopy expansion in crops and is used in lucerne (Medicago sativa L.) simulation models to predict daily PAR interception (PAR i). This then drives yield through radiation use efficiency (RUE) (Gosse et al., 1984). In perennial crops, like lucerne, the level of biomass stored in crown and taproot may affect canopy expansion in subsequent regrowth cycles (Avice et al., 1997). In temperate regions the impact of this is likely to be greatest in early-spring, when low temperatures delay development. The objective of the current research was to identify whether contrasting levels of winter biomass in …

Pillars Of Biology: 'The Genetical Evolution Of Social Behaviour, I And Ii'., Geoff Wild

Applied Mathematics Publications

None.

Adoption And Influence: Industry Evaluation Of The GrassgroTm Decision Support Tool, E. M. Salmon, A. D. Moore

IGC Proceedings (1997-2023)

The GrassGro Decision Support tool (DS tool) (Donnelly and Moore, 1999) was released for commercial use in Australia with a training package in late 1997. An assessment of its adoption was made by a survey of 53 registered users in March 1999. An evaluation of the software and training package was made at training workshops by 92 users between 1997 and December 1999. The response rates to the survey and the evaluation were 62% and 82% respectively. Seventy six percent of survey respondents had analysed at least one problem with GrassGro and 27% had applied GrassGro to five or more …

A Chance-Constrained Linear Model For Beef Policy Analysis, Claudio F. Machado, S. T. Morris, C. Dake, A. Macdonald, I. M. Brookes, F. Di Croce, F. Gonzalez, N. J. Auza

IGC Proceedings (1997-2023)

A simple linear model to evaluate different bull beef policies (BBP) by incorporating the stochastic nature of pasture yield from a database with separate chance constraints (ChC) was developed. A 100 ha farm was used, and the model was run with five different BBP and set to different levels of pasture yield risk to maximise production.ha^-1.year^-1. Summer was the most risky season, and the optimum mix of policies changed at different levels of risk. Chance constraint represents an interesting and simple alternative to include pasture variation into a linear model.

Monitoring And Modelling The Dynamics Of The Cellular Glycolysis Pathway: A Review And Future Perspectives, Nitin Patil, Hugh Byrne, Orla L. Howe, Paul A. Cahill

Articles

Background

The dynamics of the cellular glycolysis pathway underpin cellular function and dysfunction, and therefore ultimately health, disease, diagnostic and therapeutic strategies. Evolving our understanding of this fundamental process and its dynamics remains critical.

Scope of review

This paper reviews the medical relevance of glycolytic pathway in depth and explores the current state of the art for monitoring and modelling the dynamics of the process. The future perspectives of label free, vibrational microspectroscopic techniques to overcome the limitations of the current approaches are considered.

Major conclusions

Vibrational microspectroscopic techniques can potentially operate in the niche area of limitations of other …

Future Climate Streamflow Estimation In The Donnelly River Catchment, Justin Hughes, Bill Wang

Natural resources commissioned reports

The Donnelly River is located in the south-west of Western Australia. An irrigation development has been proposed in the catchment that would extract water from the Donnelly River and store this in an off stream reservoir for irrigation use. Given the known issues related to non-stationarity and hydrological prediction, the Department of Primary Industries and Regional Development (DPIRD) contracted CSIRO to review the hydrological model that was used to estimate future climate streamflow in the Donnelly River. This model was owned and operated by the Department of Water and Environmental Regulation (DWER). The CSIRO review of the model, which also …

Disentangling Diverse Responses To Climate Change Among Global Marine Ecosystem Models, Ryan F. Heneghan, Eric Galbraith, Julia L. Blanchard, Cheryl S. Harrison, Nicolas Barrier, Catherine Bulman, William Cheung, Marta Coli, Tyler D. Eddy, Maite Erauskin-Extramiana

School of Earth, Environmental, and Marine Sciences Faculty Publications and Presentations

Climate change is warming the ocean and impacting lower trophic level (LTL) organisms. Marine ecosystem models can provide estimates of how these changes will propagate to larger animals and impact societal services such as fisheries, but at present these estimates vary widely. A better understanding of what drives this inter-model variation will improve our ability to project fisheries and other ecosystem services into the future, while also helping to identify uncertainties in process understanding. Here, we explore the mechanisms that underlie the diversity of responses to changes in temperature and LTLs in eight global marine ecosystem models from the Fisheries …

Modelling Nitrogen Uptake In Winter Oilseed Rape By Using Influx Kinetics Of Nitrate Transport Systems, S. Faure, P. Malagoli, P. Lainé, E. Le Deunff, F. Ledily, A. Ourry, J. Boucaud

IGC Proceedings (1997-2023)

A mechanistic model was proposed in order to predict nitrogen uptake by a culture of oilseed rape (Brassica napus L.), using independently measured characteristics of plants growing in hydroponic or under field conditions. Uptake kinetics of the different components (Constitutive and Inducible) of the Low and High Affinity Transport Systems of nitrate (CLATS, ILATS, CHATS and IHATS, respectively) were determined by ¹⁵NO₃^- labelling in controlled conditions. The use of kinetic equations of transport systems and the experimental field data from the INRA-Châlons rape databank allowed to model NO₃^- uptake during the plant growth cycle. …

How To Cope With Global Change? On The Potential Of Ecological‐Economic Modelling For Institutional Design, Karin Frank, Birgit Müller

IGC Proceedings (1997-2023)

No abstract provided.

The Application Of Farming System Models To The Problem Of Sustainable Grasslands Management In Northern China And Australia, Randall Jones, D. Michalk, David R. Kemp, J. P. Wu, T. Takahashi, Z. F. Ma, G. Millar

IGC Proceedings (1997-2023)

No abstract provided.

Donnelly River Model Review, Justin Hughes

Natural resources commissioned reports

The Donnelly River Model was prepared for the Department of Water and Environment Regulation (DWER) by an external consultant (Hydrology and Risk Consultants) in 2018. The purpose of this model was largely to evaluate the feasibility of a proposed irrigation development centred on diversions from the Middle Donnelly near Chappel's Bridge into a reservoir in the nearby Record Brook catchment. As a part of the model build and reporting process, the HARC (2018) report was reviewed by Ecological Australia (2018) against the model specifications. ECL concluded that the model was "fit for purpose", but made many recommendations. Since re­port release, …

Sustainability Of Semi‐Arid Extensive Livestock Systems In Senegal: Elements For Modelling Animal‐Plant Interactions, G. Chirat, F. Bocquier, F. Bousquet, A. Ickowicz

IGC Proceedings (1997-2023)

No abstract provided.

Simulating Options For Managing Seasonal And Annual Variations In Feed Supply Of Mixed Crop/Livestock Systems In Sub‐Tropical Australia, Lindsay W. Bell

IGC Proceedings (1997-2023)

No abstract provided.