title: Paddock scale nitrous oxide emissions from intensively grazed pasture: Quantification and mitigation

authors: Wecking, Anne Roswitha

subjects: Greenhouse gas

abstract: Agricultural soils are the main contributor to global emissions of the potent greenhouse gas nitrous oxide (N₂O) to the atmosphere. Nitrous oxide can absorb and transform radiative energy emitted from the sun to earth into heat. The ability of N₂O to absorb energy is part of the greenhouse effect and naturally contributes to habitable temperature conditions for life on earth. Atmospheric concentrations of N₂O have never before increased as rapidly as observed since the onset of industrialisation. High N₂O concentrations enhance the greenhouse effect and, at present, add to a warming atmosphere and a changing climate. A major pathway for N₂O production is from soils that receive large surpluses of reactive nitrogen, e.g., in the form of animal excreta or fertiliser. Once available in the soil, microbes can access and transform this nitrogen into different compounds: N₂O, for example. The current contribution of agricultural soils to global N₂O emissions is about 60% but higher in New Zealand, where soils are responsible for 94% of national N₂O emissions. However, robust quantifications are not straightforward and challenging for science to overcome. This thesis is sited at the interface of this challenge and aimed at measuring the exchange of N₂O over an intensively grazed dairy pasture in New Zealand. The core of the work was based on eddy covariance (EC), a technique that allows measuring the N₂O exchange between the soil and the atmosphere at ten times per second. Since EC measurements of N₂O over dairy grazed land are rare, main objectives of this work were: to 1) compare EC to traditional measurement approaches, i.e. static chambers, 2) quantify annual N₂O emission budgets and 3) determine the effect of farm management including pasture renewal on N₂O emissions. The findings of this thesis show that EC provided a realistic picture of the N₂O exchange at paddock scales. This means EC data identified cattle grazing, land history, farm management, soil moisture and temperature as the main factors controlling N₂O exchange throughout the year. Interestingly, using one EC system for measurements across adjacent but differently managed paddocks also allowed to compare the effect of different pasture management scenarios on N₂O emissions. This will help researchers to test different mitigation options more easily in the future, ideally, to reduce N₂O emissions and avoid further atmospheric warming. This thesis advances our understanding of the N₂O exchange process from intensively grazed land as well as it shows how limited this knowledge still is. Micrometeorological N₂O flux measurements will have to be used more frequently in the future to provide researchers with answers in the face of a rapidly changing climate on earth.

text: Paddock scale nitrous oxide emissions from intensively grazed pasture: Quantification and mitigation Agricultural soils are the main contributor to global emissions of the potent greenhouse gas nitrous oxide (N₂O) to the atmosphere. Nitrous oxide can absorb and transform radiative energy emitted from the sun to earth into heat. The ability of N₂O to absorb energy is part of the greenhouse effect and naturally contributes to habitable temperature conditions for life on earth. Atmospheric concentrations of N₂O have never before increased as rapidly as observed since the onset of industrialisation. High N₂O concentrations enhance the greenhouse effect and, at present, add to a warming atmosphere and a changing climate. A major pathway for N₂O production is from soils that receive large surpluses of reactive nitrogen, e.g., in the form of animal excreta or fertiliser. Once available in the soil, microbes can access and transform this nitrogen into different compounds: N₂O, for example. The current contribution of agricultural soils to global N₂O emissions is about 60% but higher in New Zealand, where soils are responsible for 94% of national N₂O emissions. However, robust quantifications are not straightforward and challenging for science to overcome. This thesis is sited at the interface of this challenge and aimed at measuring the exchange of N₂O over an intensively grazed dairy pasture in New Zealand. The core of the work was based on eddy covariance (EC), a technique that allows measuring the N₂O exchange between the soil and the atmosphere at ten times per second. Since EC measurements of N₂O over dairy grazed land are rare, main objectives of this work were: to 1) compare EC to traditional measurement approaches, i.e. static chambers, 2) quantify annual N₂O emission budgets and 3) determine the effect of farm management including pasture renewal on N₂O emissions. The findings of this thesis show that EC provided a realistic picture of the N₂O exchange at paddock scales. This means EC data identified cattle grazing, land history, farm management, soil moisture and temperature as the main factors controlling N₂O exchange throughout the year. Interestingly, using one EC system for measurements across adjacent but differently managed paddocks also allowed to compare the effect of different pasture management scenarios on N₂O emissions. This will help researchers to test different mitigation options more easily in the future, ideally, to reduce N₂O emissions and avoid further atmospheric warming. This thesis advances our understanding of the N₂O exchange process from intensively grazed land as well as it shows how limited this knowledge still is. Micrometeorological N₂O flux measurements will have to be used more frequently in the future to provide researchers with answers in the face of a rapidly changing climate on earth.

year: 2021

title: Diorama and young people’s exploration of sustainable communities

authors: Taylor, Simon

subjects: Diorama, scientific play, agency.

abstract: This paper reports on a study using diorama constructions made by 13–14-year-olds who have been studying the topic of climate science. A diorama is a model representing a scene with three-dimensional structures, usually in miniature. The building and interaction of diorama is not the norm for students to represent their thinking of sustainable communities, however there is growing interest in representational work and multimodal reasoning which provide a springboard for scientific play, dialogue, and agency. Using a micro-ethnographic approach informed by socio-semiotic perspectives with the research of Lemke (2004), this study aimed to explore how diorama construction and the associated interaction can contribute to student reasoning and learning. Data were generated using audio recorders and multiple cameras, tracking groups of students negotiating their visual representations. The analysis proceeded through active and iterative viewing of audio and video recordings, followed by identification of themes to establish possible relationships between construction and reasoning. Through this process, the study (a) identifies multiple, necessary conditions and varied opportunities for students to enact and enable reasoning, and (b) extend current understanding of how the affordances of this visual mode interact with these conditions to contribute to student learning of climate science.

text: Diorama and young people’s exploration of sustainable communities This paper reports on a study using diorama constructions made by 13–14-year-olds who have been studying the topic of climate science. A diorama is a model representing a scene with three-dimensional structures, usually in miniature. The building and interaction of diorama is not the norm for students to represent their thinking of sustainable communities, however there is growing interest in representational work and multimodal reasoning which provide a springboard for scientific play, dialogue, and agency. Using a micro-ethnographic approach informed by socio-semiotic perspectives with the research of Lemke (2004), this study aimed to explore how diorama construction and the associated interaction can contribute to student reasoning and learning. Data were generated using audio recorders and multiple cameras, tracking groups of students negotiating their visual representations. The analysis proceeded through active and iterative viewing of audio and video recordings, followed by identification of themes to establish possible relationships between construction and reasoning. Through this process, the study (a) identifies multiple, necessary conditions and varied opportunities for students to enact and enable reasoning, and (b) extend current understanding of how the affordances of this visual mode interact with these conditions to contribute to student learning of climate science.

year: 2023-11-21

title: Secondary school subject choice: an ethnographic study

authors: Darnell, Doreen Anne

abstract: This study of subject choice followed two groups of pupils through the decision-making process at two state, co-educational high schools in the North Island of New Zealand. The high schools were similar in size, location, ethnic composition and range of home background of pupils, but had differing option systems. 
At the end of their form two year, 53 children (27 boys, 26 girls) were interviewed at their respective primary or intermediate schools while they were considering the options offered to them in form three at one of the two high schools. The children were re-interviewed the following year at their respective high schools. A further 37 pupils (17 boys, 20 girls) were interviewed in form four at their respective high schools while they were choosing fifth form subjects and were re-interviewed the following year after they had experienced the subjects they had chosen. All children in the study were chosen by their teachers as being representative of the range of pupils at their schools, in terms of ability, ethnic origin and home background. 
In addition, parents of eight of the younger children were interviewed in their homes and 31 teachers, representing all the subjects offered to the children at the two high schools, were interviewed at their respective schools. 
Analysis of interview transcripts showed that pupils’ decisions were influenced by the structure of the option systems, the attitudes of parents and peers and by the overt and covert actions of teachers. Access to information was found to be a key component of decision making. Children’s and parents’ views about the school subjects showed a strong measure of agreement, but there was less agreement between children’ views and teachers’ views. 
A model of decision making was elicited from the data and case studies illustrated the range of pupils’ individual experience, in particular, the experience of Maori pupils identified as ‘winners’ and ‘losers’ in the school system.

text: Secondary school subject choice: an ethnographic study This study of subject choice followed two groups of pupils through the decision-making process at two state, co-educational high schools in the North Island of New Zealand. The high schools were similar in size, location, ethnic composition and range of home background of pupils, but had differing option systems. 
At the end of their form two year, 53 children (27 boys, 26 girls) were interviewed at their respective primary or intermediate schools while they were considering the options offered to them in form three at one of the two high schools. The children were re-interviewed the following year at their respective high schools. A further 37 pupils (17 boys, 20 girls) were interviewed in form four at their respective high schools while they were choosing fifth form subjects and were re-interviewed the following year after they had experienced the subjects they had chosen. All children in the study were chosen by their teachers as being representative of the range of pupils at their schools, in terms of ability, ethnic origin and home background. 
In addition, parents of eight of the younger children were interviewed in their homes and 31 teachers, representing all the subjects offered to the children at the two high schools, were interviewed at their respective schools. 
Analysis of interview transcripts showed that pupils’ decisions were influenced by the structure of the option systems, the attitudes of parents and peers and by the overt and covert actions of teachers. Access to information was found to be a key component of decision making. Children’s and parents’ views about the school subjects showed a strong measure of agreement, but there was less agreement between children’ views and teachers’ views. 
A model of decision making was elicited from the data and case studies illustrated the range of pupils’ individual experience, in particular, the experience of Maori pupils identified as ‘winners’ and ‘losers’ in the school system.

year: 1985