Climate sensitivity of the complex dynamics of the green spruce aphid-Spruce plantation interactions: Insight from a new mechanistic model.

Aphids can have a significant impact on the growth and commercial yield of spruce plantations. Here we develop a mechanistic deterministic mathematical model for the dynamics of the green spruce aphid (Elatobium abietum Walker) growing on Sitka spruce (Picea sitchensis (Bong.) Carr.

Exploration of bimodal kinetics in marker digesta outflows using compartmental models.

A deterministic compartmental model is developed for examining the dynamics of digesta marker outflows in animals, focussing on models which will simulate bimodal kinetics with two peaks in the time course of marker outflow. First, to establish the background to the subsequent modelling of bimodal flow, we examine the compartmental scheme which gives rise mechanistically to the gamma function, and derive or describe various useful properties. This is illustrated by varying two key parameters of the gamma function, n (the number of compartments), and k (the rate constant for compartment emptying).

Blue tongue - A modelling examination of fundamentals - Seasonality and chaos.

A deterministic mathematical model is developed for the dynamics of bluetongue disease within a single farm. The purpose is to examine widely the possible behaviours which may occur. This is important because of the increasing impact of blue tongue due to global warming.

Allocation of new growth between shoot, root and mycorrhiza in relation to carbon, nitrogen and phosphate supply: teleonomy with maximum growth rate.

Treating resource allocation within plants, and between plants and associated organisms, is essential for plant, crop and ecosystem modelling. However, it is still an unresolved issue. It is also important to consider quantitatively when it is efficient and to what extent a plant can invest profitably in a mycorrhizal association.

Mathematical model of fructan biosynthesis and polymer length distribution in plants.

Background And Aims: There are many unresolved issues concerning the biochemistry of fructan biosynthesis. The aim of this paper is to address some of these by means of modelling mathematically the biochemical processes.

Methods: A model has been constructed for the step-by-step synthesis of fructan polymers.

Plant growth and respiration re-visited: maintenance respiration defined - it is an emergent property of, not a separate process within, the system - and why the respiration : photosynthesis ratio is conservative.

Background And Aims: Plant growth and respiration still has unresolved issues, examined here using a model. The aims of this work are to compare the model's predictions with McCree's observation-based respiration equation which led to the 'growth respiration/maintenance respiration paradigm' (GMRP) - this is required to give the model credibility; to clarify the nature of maintenance respiration (MR) using a model which does not represent MR explicitly; and to examine algebraic and numerical predictions for the respiration:photosynthesis ratio.

Methods: A two-state variable growth model is constructed, with structure and substrate, applicable on plant to ecosystem scales.

A model of canopy photosynthesis incorporating protein distribution through the canopy and its acclimation to light, temperature and CO2.

Background And Aims: The distribution of photosynthetic enzymes, or nitrogen, through the canopy affects canopy photosynthesis, as well as plant quality and nitrogen demand. Most canopy photosynthesis models assume an exponential distribution of nitrogen, or protein, through the canopy, although this is rarely consistent with experimental observation. Previous optimization schemes to derive the nitrogen distribution through the canopy generally focus on the distribution of a fixed amount of total nitrogen, which fails to account for the variation in both the actual quantity of nitrogen in response to environmental conditions and the interaction of photosynthesis and respiration at similar levels of complexity.

Modelling foot and mouth disease.

A simple generic model of foot and mouth disease (FMD) is presented. The dynamics of FMD at the index site (the farm where the initial infection occurs) is represented. Spread of disease from the index site is simulated with a three-term radial function, the terms corresponding to natural processes, short- and long-range movements.

Disruption of colonic barrier function and induction of mediator release by strains of Campylobacter jejuni that invade epithelial cells.

Aim: To study the mechanisms by which Campylobacter jejuni (C. jejuni) causes inflammation and diarrhea. In particular, direct interactions with intestinal epithelial cells and effects on barrier function are poorly under-stood.