title: Semi-mechanistic modelling in nonlinear regression: a case study

authors: Domijan, Katarina

subjects: statistics

abstract: This paper discusses the use of highly parameterized semi-mechanistic nonlinear models with particular reference to the PARJIB crop response model of Reid (2002)[Yield response to nutrient supply across a wide range of conditions 1. Model derivation. Field Crops Research77, 161–171]. Compared to empirical linear approaches, such models promise improved generality of application but present considerable challenges for estimation. Some success has been achieved with a fitting approach that uses a Levenberg–Marquardt algorithm starting from initial values determined by a genetic algorithm. Attention must be paid, however, to correlations between parameter estimates and an approach is described to identify these based on large simulated datasets. This work illustrates the value for the scientist in exploring the correlation structure in mechanistic or semi-mechanistic models. Such information might be used to reappraise the structure of the model itself, especially if the experimental evidence is not strong enough to allow estimation of a parameter free of assumptions about the values of others. Thus statistical modelling and analysis can complement mechanistic studies, making more explicit what is known and what is not known about the processes being modelled and guiding further research.

text: Semi-mechanistic modelling in nonlinear regression: a case study This paper discusses the use of highly parameterized semi-mechanistic nonlinear models with particular reference to the PARJIB crop response model of Reid (2002)[Yield response to nutrient supply across a wide range of conditions 1. Model derivation. Field Crops Research77, 161–171]. Compared to empirical linear approaches, such models promise improved generality of application but present considerable challenges for estimation. Some success has been achieved with a fitting approach that uses a Levenberg–Marquardt algorithm starting from initial values determined by a genetic algorithm. Attention must be paid, however, to correlations between parameter estimates and an approach is described to identify these based on large simulated datasets. This work illustrates the value for the scientist in exploring the correlation structure in mechanistic or semi-mechanistic models. Such information might be used to reappraise the structure of the model itself, especially if the experimental evidence is not strong enough to allow estimation of a parameter free of assumptions about the values of others. Thus statistical modelling and analysis can complement mechanistic studies, making more explicit what is known and what is not known about the processes being modelled and guiding further research.

year: 2006

title: Assessing habitat suitability for karure | kakaruia | Chatham Island black robin (Petroica traversi): Integrating invertebrate surveys, DNA metabarcoding, and foraging ecology

authors: Teague, Caleb

subjects: Chatham Islands

abstract: The karure | kakaruia | Chatham Island black robin (Petroica traversi) is one of New Zealand's most remarkable conservation achievements, recovering from a mere five birds in 1980 to around 330 today. However, the species remains Nationally Critical and restricted to two small islands, making establishment of additional populations essential for long-term prosperity. A previous translocation attempt to Rangiauria | Rangiaotea |Pitt Island failed, with inadequate food resources hypothesised as a contributing factor, yet black robin dietary requirements and prey availability at potential translocation sites remain poorly understood. This study integrated invertebrate community surveys, DNA metabarcoding of faecal samples, and behavioural observations to characterise black robin diet, foraging behaviour and food availability, aiming to assess habitat suitability across the Chatham Islands. 
In Chapter Two I examined invertebrate communities across four forested sites across the Chatham Island archipelago; the currently inhabited Woolshed Bush and Top Bush on Hokorereoro | Rangatira | Southeast Island, previously failed translocation site Elizabeth Ellen Preece Conservation Covenant | Caravan Bush on Rangiauria | Rangiaotea | Pitt Island, and potential future translocation site Chudleigh Conservation Area on Rēkohu | Wharekauri | Chatham Island. Analyses revealed that predator free sites (Woolshed Bush and Top Bush) supported significantly higher ground-active invertebrate biomass. This difference was driven by large-bodied cave wētā and ground beetles, which were abundant on Rangatira Island but absent from Caravan Bush and Chudleigh Conservation Area. Surprisingly, Woolshed Bush and Top Bush showed similar invertebrate communities despite different black robin densities, indicating that prey availability alone does not determine habitat quality.
DNA metabarcoding of faecal samples in Chapter Three revealed that black robin are generalist insectivores, with Coleoptera, Diptera, and Orthoptera comprising the majority of their diet. Dietary composition showed no significant differences between sites, indicating consistent resource use across Woolshed Bush and Top Bush. Foraging observations confirmed strong ground-level preferences, with 82.2% of foraging events occurring at ground level, emphasising the importance of intact forest floor environments for future translocation sites.
This research demonstrates that black robin persistence depends on multiple interacting factors. Future translocation sites should include abundant large-bodied prey, intact forest floors with deep leaf litter supporting ground foraging, effective predator control or predator-free status, and mature forest structure. DNA metabarcoding proved essential for revealing dietary composition that would be impossible to detect through observation alone by characterising consumption of cryptic prey taxa. While food availability is necessary for translocation success, it is not a sole determining factor; other habitat features such as nest site availability and predator presence must also be considered. The methods I have established here provide a repeatable framework for evidence-based translocation planning.

text: Assessing habitat suitability for karure | kakaruia | Chatham Island black robin (Petroica traversi): Integrating invertebrate surveys, DNA metabarcoding, and foraging ecology The karure | kakaruia | Chatham Island black robin (Petroica traversi) is one of New Zealand's most remarkable conservation achievements, recovering from a mere five birds in 1980 to around 330 today. However, the species remains Nationally Critical and restricted to two small islands, making establishment of additional populations essential for long-term prosperity. A previous translocation attempt to Rangiauria | Rangiaotea |Pitt Island failed, with inadequate food resources hypothesised as a contributing factor, yet black robin dietary requirements and prey availability at potential translocation sites remain poorly understood. This study integrated invertebrate community surveys, DNA metabarcoding of faecal samples, and behavioural observations to characterise black robin diet, foraging behaviour and food availability, aiming to assess habitat suitability across the Chatham Islands. 
In Chapter Two I examined invertebrate communities across four forested sites across the Chatham Island archipelago; the currently inhabited Woolshed Bush and Top Bush on Hokorereoro | Rangatira | Southeast Island, previously failed translocation site Elizabeth Ellen Preece Conservation Covenant | Caravan Bush on Rangiauria | Rangiaotea | Pitt Island, and potential future translocation site Chudleigh Conservation Area on Rēkohu | Wharekauri | Chatham Island. Analyses revealed that predator free sites (Woolshed Bush and Top Bush) supported significantly higher ground-active invertebrate biomass. This difference was driven by large-bodied cave wētā and ground beetles, which were abundant on Rangatira Island but absent from Caravan Bush and Chudleigh Conservation Area. Surprisingly, Woolshed Bush and Top Bush showed similar invertebrate communities despite different black robin densities, indicating that prey availability alone does not determine habitat quality.
DNA metabarcoding of faecal samples in Chapter Three revealed that black robin are generalist insectivores, with Coleoptera, Diptera, and Orthoptera comprising the majority of their diet. Dietary composition showed no significant differences between sites, indicating consistent resource use across Woolshed Bush and Top Bush. Foraging observations confirmed strong ground-level preferences, with 82.2% of foraging events occurring at ground level, emphasising the importance of intact forest floor environments for future translocation sites.
This research demonstrates that black robin persistence depends on multiple interacting factors. Future translocation sites should include abundant large-bodied prey, intact forest floors with deep leaf litter supporting ground foraging, effective predator control or predator-free status, and mature forest structure. DNA metabarcoding proved essential for revealing dietary composition that would be impossible to detect through observation alone by characterising consumption of cryptic prey taxa. While food availability is necessary for translocation success, it is not a sole determining factor; other habitat features such as nest site availability and predator presence must also be considered. The methods I have established here provide a repeatable framework for evidence-based translocation planning.

year: 2026

title: Action for improvement in our own contexts

authors: Bruce Ferguson, Pip

subjects: education

abstract: Discusses: The pedagogy of Paulo Freire – importance of emancipatory, not ‘banking’, education. Who needs emancipatory education in NZ, and why? Consideration of issues affecting Māori success in the New Zealand education system.

text: Action for improvement in our own contexts Discusses: The pedagogy of Paulo Freire – importance of emancipatory, not ‘banking’, education. Who needs emancipatory education in NZ, and why? Consideration of issues affecting Māori success in the New Zealand education system.

year: 2012