title: Modifying hydrological regime and catchment land use to improve water quality in Lake Waikare: Modelled insights

authors: Prentice, Matthew James

abstract: Effective management of eutrophication in large, shallow, lakes is particularly challenging, especially in catchments dominated by agricultural activities. These challenges are further exacerbated in lakes that have undergone significant hydrological and biogeochemical modification. In these systems, effective hydrological management strategies may involve increasing discharge rates to promote flushing and modifying lake depth to reduce the effects of wind-induced sediment resuspension, while effective biogeochemical modification may involve improving catchment management practices to reduce external nutrient loading. In this study, we present a modelling investigation of Lake Waikare, Waikato, New Zealand; a large (surface area: 34 km²), shallow (mean depth: 1.2 m), hypereutrophic lake that has experienced significant hydrological modification and water quality deterioration since the early 1900s.

text: Modifying hydrological regime and catchment land use to improve water quality in Lake Waikare: Modelled insights Effective management of eutrophication in large, shallow, lakes is particularly challenging, especially in catchments dominated by agricultural activities. These challenges are further exacerbated in lakes that have undergone significant hydrological and biogeochemical modification. In these systems, effective hydrological management strategies may involve increasing discharge rates to promote flushing and modifying lake depth to reduce the effects of wind-induced sediment resuspension, while effective biogeochemical modification may involve improving catchment management practices to reduce external nutrient loading. In this study, we present a modelling investigation of Lake Waikare, Waikato, New Zealand; a large (surface area: 34 km²), shallow (mean depth: 1.2 m), hypereutrophic lake that has experienced significant hydrological modification and water quality deterioration since the early 1900s.

year: 2025

title: Studies on carbon and DNA preservation in allophanic soils and paleosols on Holocene tephras in New Zealand

authors: Huang, Yu-Tuan

abstract: The recovery of ancient DNA (aDNA) and palaeoenvironmental DNA (PalEnDNA) from soils and sediments has enabled detailed paleontological and ecological records to be obtained. Because of the superior ability of allophanic soils and Andisols to adsorb considerable soil organic matter (SOM), and to slow the rate of carbon turnover in such soils, I hypothesised that environmental DNA can be preserved in allophanic soils and Andisols together with SOM, and that such DNA may be able to help reveal past environments. I characterised the preserved SOM in stratigraphic successions of buried paleosols on Holocene tephras of known age in northern New Zealand and attempted to extract and analyse the DNA to search for possible PalEnDNA.

Using synchrotron radiation-based carbon near-edge X-ray absorption fine structure (C NEXAFS) spectroscopy, I found the compositions and proportions of carbon functional groups of SOM in allophanic paleosols on precisely-dated Holocene tephras (c. 12,000 to 1718 calendar [cal] years BP) at four sites in northern New Zealand were similar and dominated by carboxylic functional groups, with subordinate amounts of quinonic, aromatic, and aliphatic groups. Differences in clay and allophane contents, stratigraphic position, age, parenttephra composition (andesitic versus rhyolitic), and mode of soil origin (retardant versus developmental upbuilding pedogenesis) seemed not to affect the structure of SOM over time. The similarity of the SOM in allophanic paleosols of different ages implied its preservation in allophanic soils over a long time, and the presence of quinonic carbon, normally very susceptible to degradation and transformation, shows that the allophanic soils have protected it very effectively. The quinonic carbon in buried horizons is thus indicative of the preservation of biological materials originating from bacteria and plants. The SOM originated through upbuilding pedogenesis: as soil genesis began in a newly-deposited tephra at the soil surface, allophane formed and it sequestered SOM from the modern (surface) organic cycle dominated by inputs from broadleaf-podocarp forest. Ongoing tephra deposition then caused the land surface to rise so that once-surface horizons were buried more deeply and hence became increasingly divorced from the modern organic cycle over time. The SOM adsorbed when the soil horizon was at the land surface was preserved in the buried soils because a fractal pore network of allophane aggregates and nanopores encapsulated and shielded the ‘old’ or relict SOM (including quinonic carbon) derived from past environments of the Holocene.

To provide fundamental knowledge about the interaction of allophane, DNA, and SOM in soils, I examined the adsorption capacity and adsorption mechanisms of salmon-sperm DNA on pure synthetic allophane and humic acidrich synthetic allophane. The pure synthetic allophane was able to adsorb up to 34 μg/mg of salmon-sperm DNA, but the humic acid-rich synthetic allophane adsorbed only 3.5 μg/mg of salmon-sperm DNA. Salmon-sperm DNA was adsorbed chemically through its phosphate group to the aluminol groups of synthetic allophane, and adsorbed chemically through humic acid covering the synthetic allophane spherules, and thus became bound indirectly to synthetic allophane. The chemical adsorption of salmon-sperm DNA on synthetic allophane led to the aggregation of allophane spherules to form nanoaggregates and microaggregates, and ~80% of total adsorbed DNA on allophane was held physically within the interstices (pores) between allophane spherules and nanoaggregates. The encapsulated DNA within the stable allophane-DNA aggregates may not be accessible to enzymes nor microbes, hence enabling DNA protection and preservation in allophanic soils. By implication, organic carbon is therefore likely to be sequestered and protected in allophanic soils (Andisols) in the same way as demonstrated here for DNA − that is, predominantly by encapsulation within a tortuous network of nanopores and submicropores amidst stable nanoaggregates and microaggregates, rather than by chemisorption alone.

A novel two-step method was developed to isolate DNA from allophane, based in part on experiments devised to extract salmon-sperm DNA from synthetic allophane. The two-step method for DNA extraction from allophanic soils is based on (1) chelating DNA and blocking adsorptive sites on allophane using EDTA and phosphate, respectively, and (2) dissolving allophane using acidified ammonium oxalate. The DNA yield from three allophanic paleosols on Holocene tephras was up to 44.5 μg/g soil (oven-dry basis). The extracted DNA was then successfully purified via gel electrophoresis followed by a gel purification kit, and the amplifiable and sequenced DNA extracted from a paleosol (which had been at the land surface for around 4000 years between c. 9423 and c. 5526 calendar years BP) on Rotoma tephra contained New Zealand endemic and exotic plants that differed from the European grasses growing currently on the land surface. The difference in vegetation indicates that the DNA extraction method I (with others) have developed is able to access environmental DNA originating from previous vegetation cover. The DNA extraction method could be used to facilitate the search for possible PalEnDNA in allophanic paleosols for reconstructing the past terrestrial environments as well as to investigate the biodiversity in allophanic soils and the origins of SOM.

Allophanic soils are demonstrably able to protect environmental DNA from degradation for a long period of time, and such DNA is able to reveal past environments. However, the duration over which that environmental DNA can be preserved in allophanic soils needs to be resolved, and additional investigations of gene diversity in allophanic paleosols of different ages using high-throughput sequencing (HTS) are required to determine the taxonomic profiles recovered in paleosols and to rule out contamination of modern DNA.

text: Studies on carbon and DNA preservation in allophanic soils and paleosols on Holocene tephras in New Zealand The recovery of ancient DNA (aDNA) and palaeoenvironmental DNA (PalEnDNA) from soils and sediments has enabled detailed paleontological and ecological records to be obtained. Because of the superior ability of allophanic soils and Andisols to adsorb considerable soil organic matter (SOM), and to slow the rate of carbon turnover in such soils, I hypothesised that environmental DNA can be preserved in allophanic soils and Andisols together with SOM, and that such DNA may be able to help reveal past environments. I characterised the preserved SOM in stratigraphic successions of buried paleosols on Holocene tephras of known age in northern New Zealand and attempted to extract and analyse the DNA to search for possible PalEnDNA.

Using synchrotron radiation-based carbon near-edge X-ray absorption fine structure (C NEXAFS) spectroscopy, I found the compositions and proportions of carbon functional groups of SOM in allophanic paleosols on precisely-dated Holocene tephras (c. 12,000 to 1718 calendar [cal] years BP) at four sites in northern New Zealand were similar and dominated by carboxylic functional groups, with subordinate amounts of quinonic, aromatic, and aliphatic groups. Differences in clay and allophane contents, stratigraphic position, age, parenttephra composition (andesitic versus rhyolitic), and mode of soil origin (retardant versus developmental upbuilding pedogenesis) seemed not to affect the structure of SOM over time. The similarity of the SOM in allophanic paleosols of different ages implied its preservation in allophanic soils over a long time, and the presence of quinonic carbon, normally very susceptible to degradation and transformation, shows that the allophanic soils have protected it very effectively. The quinonic carbon in buried horizons is thus indicative of the preservation of biological materials originating from bacteria and plants. The SOM originated through upbuilding pedogenesis: as soil genesis began in a newly-deposited tephra at the soil surface, allophane formed and it sequestered SOM from the modern (surface) organic cycle dominated by inputs from broadleaf-podocarp forest. Ongoing tephra deposition then caused the land surface to rise so that once-surface horizons were buried more deeply and hence became increasingly divorced from the modern organic cycle over time. The SOM adsorbed when the soil horizon was at the land surface was preserved in the buried soils because a fractal pore network of allophane aggregates and nanopores encapsulated and shielded the ‘old’ or relict SOM (including quinonic carbon) derived from past environments of the Holocene.

To provide fundamental knowledge about the interaction of allophane, DNA, and SOM in soils, I examined the adsorption capacity and adsorption mechanisms of salmon-sperm DNA on pure synthetic allophane and humic acidrich synthetic allophane. The pure synthetic allophane was able to adsorb up to 34 μg/mg of salmon-sperm DNA, but the humic acid-rich synthetic allophane adsorbed only 3.5 μg/mg of salmon-sperm DNA. Salmon-sperm DNA was adsorbed chemically through its phosphate group to the aluminol groups of synthetic allophane, and adsorbed chemically through humic acid covering the synthetic allophane spherules, and thus became bound indirectly to synthetic allophane. The chemical adsorption of salmon-sperm DNA on synthetic allophane led to the aggregation of allophane spherules to form nanoaggregates and microaggregates, and ~80% of total adsorbed DNA on allophane was held physically within the interstices (pores) between allophane spherules and nanoaggregates. The encapsulated DNA within the stable allophane-DNA aggregates may not be accessible to enzymes nor microbes, hence enabling DNA protection and preservation in allophanic soils. By implication, organic carbon is therefore likely to be sequestered and protected in allophanic soils (Andisols) in the same way as demonstrated here for DNA − that is, predominantly by encapsulation within a tortuous network of nanopores and submicropores amidst stable nanoaggregates and microaggregates, rather than by chemisorption alone.

A novel two-step method was developed to isolate DNA from allophane, based in part on experiments devised to extract salmon-sperm DNA from synthetic allophane. The two-step method for DNA extraction from allophanic soils is based on (1) chelating DNA and blocking adsorptive sites on allophane using EDTA and phosphate, respectively, and (2) dissolving allophane using acidified ammonium oxalate. The DNA yield from three allophanic paleosols on Holocene tephras was up to 44.5 μg/g soil (oven-dry basis). The extracted DNA was then successfully purified via gel electrophoresis followed by a gel purification kit, and the amplifiable and sequenced DNA extracted from a paleosol (which had been at the land surface for around 4000 years between c. 9423 and c. 5526 calendar years BP) on Rotoma tephra contained New Zealand endemic and exotic plants that differed from the European grasses growing currently on the land surface. The difference in vegetation indicates that the DNA extraction method I (with others) have developed is able to access environmental DNA originating from previous vegetation cover. The DNA extraction method could be used to facilitate the search for possible PalEnDNA in allophanic paleosols for reconstructing the past terrestrial environments as well as to investigate the biodiversity in allophanic soils and the origins of SOM.

Allophanic soils are demonstrably able to protect environmental DNA from degradation for a long period of time, and such DNA is able to reveal past environments. However, the duration over which that environmental DNA can be preserved in allophanic soils needs to be resolved, and additional investigations of gene diversity in allophanic paleosols of different ages using high-throughput sequencing (HTS) are required to determine the taxonomic profiles recovered in paleosols and to rule out contamination of modern DNA.

year: 2016

title: “On and On It Goes”: Representations of the New Zealand Wars in novels, film, and theatre

authors: Sheridan, Brendan Daniel

subjects: History

abstract: This thesis considers fictional representations of the New Zealand Wars. Through the media of novels, feature films, and drama with links to Shakespeare, it explores common features between representations. It examines how these representations change in tone or style over time and how different representations negotiate the complex issues of race, gender, and colonialism.
	I examine key representations ranging from 1861 to 2017 in terms of genre. I begin with the nineteenth-century novel as many of the key tropes used in representations of the New Zealand Wars emerge in this period. I then look at the twentieth-century novel, before concentrating specifically on Maurice Shadbolt and Witi Ihimaera. My discussion then turns to the genres of film and theatre. In all of these diverse representations there are recurring tropes and motifs. Many of the fictions feature stock characters such as the European traveller, the imperial official, and the Māori maiden and bear the imprint of historical romance conventions, popularised by Sir Walter Scott’s Waverly and James Fenimore Cooper’s The Last of the Mohicans. The vast majority of stories take place in the North Island between 1860 and 1870. Variations in the depiction of historical events are shaped by the historical scholarship and dominant ideologies of the time, such as the post-colonial tonal shift that emerges following the publication of work by James Belich and Ranginui Walker. I contextualise representations with their point in history, and how they treat the New Zealand Wars in terms of events, characters, and historical figures. 
	Through this approach, my thesis argues that representations of the New Zealand Wars do not form themselves in isolation and do not occur in isolated clusters. This thesis seeks to demonstrate that representations of the New Zealand Wars occur on a steady continuum. Representations of the conflict exist in parallel to one another (intentional or not) and are affected by the social climate, dominant ideologies, and published histories available to the author at the time of writing. The variety of representations—novel, feature film, stage play—share many core tropes. Even so, chronologically this continuum also features shifts in tone, ideologies, and sympathies. A novel of the 1980s has a very different perspective regarding settlers compared to a novel from the 1860s. In the same manner, a play staged in the 2000s shows a different attitude towards the conflict compared to a film from the 1940s. This thesis demonstrates that while representations of the New Zealand Wars share a common subject, how they approach the material is constantly evolving.

text: “On and On It Goes”: Representations of the New Zealand Wars in novels, film, and theatre This thesis considers fictional representations of the New Zealand Wars. Through the media of novels, feature films, and drama with links to Shakespeare, it explores common features between representations. It examines how these representations change in tone or style over time and how different representations negotiate the complex issues of race, gender, and colonialism.
	I examine key representations ranging from 1861 to 2017 in terms of genre. I begin with the nineteenth-century novel as many of the key tropes used in representations of the New Zealand Wars emerge in this period. I then look at the twentieth-century novel, before concentrating specifically on Maurice Shadbolt and Witi Ihimaera. My discussion then turns to the genres of film and theatre. In all of these diverse representations there are recurring tropes and motifs. Many of the fictions feature stock characters such as the European traveller, the imperial official, and the Māori maiden and bear the imprint of historical romance conventions, popularised by Sir Walter Scott’s Waverly and James Fenimore Cooper’s The Last of the Mohicans. The vast majority of stories take place in the North Island between 1860 and 1870. Variations in the depiction of historical events are shaped by the historical scholarship and dominant ideologies of the time, such as the post-colonial tonal shift that emerges following the publication of work by James Belich and Ranginui Walker. I contextualise representations with their point in history, and how they treat the New Zealand Wars in terms of events, characters, and historical figures. 
	Through this approach, my thesis argues that representations of the New Zealand Wars do not form themselves in isolation and do not occur in isolated clusters. This thesis seeks to demonstrate that representations of the New Zealand Wars occur on a steady continuum. Representations of the conflict exist in parallel to one another (intentional or not) and are affected by the social climate, dominant ideologies, and published histories available to the author at the time of writing. The variety of representations—novel, feature film, stage play—share many core tropes. Even so, chronologically this continuum also features shifts in tone, ideologies, and sympathies. A novel of the 1980s has a very different perspective regarding settlers compared to a novel from the 1860s. In the same manner, a play staged in the 2000s shows a different attitude towards the conflict compared to a film from the 1940s. This thesis demonstrates that while representations of the New Zealand Wars share a common subject, how they approach the material is constantly evolving.

year: 2019