title: Photodegradation leads to increased carbon dioxide losses from terrestrial organic matter

authors: Rutledge, Susanna

subjects: abiotic decomposition

abstract: CO₂ production in terrestrial ecosystems is generally assumed to be solely biologically driven while the role of abiotic processes has been largely overlooked. In addition to microbial decomposition, photodegradation – the direct breakdown of organic matter (OM) by solar irradiance – has been found to contribute to litter mass loss in dry ecosystems. Previous small-scale studies have shown that litter degradation by irradiance is accompanied by emissions of CO₂. However, the contribution of photodegradation to total CO₂ losses at ecosystems scales is unknown. This study determined the proportion of the total CO₂ losses caused by photodegradation in two ecosystems: a bare peatland in New Zealand and a seasonally dry grassland in California. The direct effect of solar irradiance on CO₂  production was examined by comparing daytime CO₂  fluxes measured using eddy covariance (EC) systems with simultaneous measurements made using an opaque chamber and the soil CO₂ gradient technique, and with night-time EC measurements under the same soil temperature and moisture conditions. In addition, a transparent chamber was used to directly measure CO₂ fluxes from OM caused by solar irradiance. Photodegradation contributed 19% of the annual CO₂ flux from the peatland and almost 60% of the dry season CO₂ flux from the grassland, and up to 62% and 92% of the summer mid-day CO₂ fluxes, respectively. Our results suggest that photodegradation may be important in a wide range of ecosystems with exposed OM. Furthermore, the practice of partitioning daytime ecosystem CO₂ exchange into its gross components by assuming that total daytime CO₂ losses can be approximated using estimates of biological respiration alone may be in error. To obtain robust estimates of global ecosystem–atmosphere carbon transfers, the contribution of photodegradation to OM decomposition must be quantified for other ecosystems and the results incorporated into coupled carbon–climate models.

text: Photodegradation leads to increased carbon dioxide losses from terrestrial organic matter CO₂ production in terrestrial ecosystems is generally assumed to be solely biologically driven while the role of abiotic processes has been largely overlooked. In addition to microbial decomposition, photodegradation – the direct breakdown of organic matter (OM) by solar irradiance – has been found to contribute to litter mass loss in dry ecosystems. Previous small-scale studies have shown that litter degradation by irradiance is accompanied by emissions of CO₂. However, the contribution of photodegradation to total CO₂ losses at ecosystems scales is unknown. This study determined the proportion of the total CO₂ losses caused by photodegradation in two ecosystems: a bare peatland in New Zealand and a seasonally dry grassland in California. The direct effect of solar irradiance on CO₂  production was examined by comparing daytime CO₂  fluxes measured using eddy covariance (EC) systems with simultaneous measurements made using an opaque chamber and the soil CO₂ gradient technique, and with night-time EC measurements under the same soil temperature and moisture conditions. In addition, a transparent chamber was used to directly measure CO₂ fluxes from OM caused by solar irradiance. Photodegradation contributed 19% of the annual CO₂ flux from the peatland and almost 60% of the dry season CO₂ flux from the grassland, and up to 62% and 92% of the summer mid-day CO₂ fluxes, respectively. Our results suggest that photodegradation may be important in a wide range of ecosystems with exposed OM. Furthermore, the practice of partitioning daytime ecosystem CO₂ exchange into its gross components by assuming that total daytime CO₂ losses can be approximated using estimates of biological respiration alone may be in error. To obtain robust estimates of global ecosystem–atmosphere carbon transfers, the contribution of photodegradation to OM decomposition must be quantified for other ecosystems and the results incorporated into coupled carbon–climate models.

year: 2009

title: Characteristics of sub-surface sediments in southern Stella Passage, Tauranga Harbour

authors: Moon, Vicki G.

abstract: The Port of Tauranga is considering port developments that would require capital dredging of a section of the southern Stella Passage to achieve depths comparable to the northern Stella Passage. Seismic profiles, core samples, and	CPT data were	collected by the University of Waikato and OPUS for the area impacted by proposed development.

The core samples were analysed for sediment texture, including assessment	of the fines (silt + clay) content. Four main stratigraphic	units were identified from the available data. These were, in order of increasing stratigraphic depth and age: Holocene sand; Pleistocene alluvial fan; Pleistocene organic silt; and Pleistocene terrestrial and shallow marine sand. In general, the fines content increased with depth and age. Younger units thin southwards along Stella Passage, resulting in increasing fines content southwards along the channel.

text: Characteristics of sub-surface sediments in southern Stella Passage, Tauranga Harbour The Port of Tauranga is considering port developments that would require capital dredging of a section of the southern Stella Passage to achieve depths comparable to the northern Stella Passage. Seismic profiles, core samples, and	CPT data were	collected by the University of Waikato and OPUS for the area impacted by proposed development.

The core samples were analysed for sediment texture, including assessment	of the fines (silt + clay) content. Four main stratigraphic	units were identified from the available data. These were, in order of increasing stratigraphic depth and age: Holocene sand; Pleistocene alluvial fan; Pleistocene organic silt; and Pleistocene terrestrial and shallow marine sand. In general, the fines content increased with depth and age. Younger units thin southwards along Stella Passage, resulting in increasing fines content southwards along the channel.

year: 2019

title: Weaving Mātauranga Māori into climate change education with primary school students in New Zealand

authors: Jackson, Ryan

abstract: This thesis explores the integration of Indigenous knowledge, specifically mātauranga Māori, into climate change education for primary school children in Aotearoa (New Zealand). It engages with pūrākau (verbal narratives that encode knowledge) gifted by the local hapū (Rangitāne sub-tribe) to a kura (school). The study contributes to the growing body of research that addresses a gap in research and teaching practice, which, despite global calls for action, remains inconsistent in teaching at this age level or lacks direct curriculum guidance in Aotearoa.

The main question for this study was: In what ways can Rangitāne pūrākau engage and further the understanding of Year five and six ākonga (learners) in learning about climate change within a kura in the lower North Island of Aotearoa?

This research used a mix of different research methods to explore this question. A learning intervention wove a pūrākau, climate change concepts and kai (food) together to create a ten-week learning programme. This learning intervention was then implemented by a kaiako (teacher) with a group of 21 Year five and six ākonga. Data were collected using pre- and post-tests to assess what students learned during the learning intervention, a group interview with the ākonga to hear their voices in the study, and an interview with their kaiako to gain insights into how engaged the ākonga were, their opinion on their understandings, and how aspects of the intervention went.

Analysis of the findings shows that the use of pūrākau and other forms of mātauranga Māori helped ākonga connect deeply with the material, which contributed positively to their engagement and to them gaining a sound understanding of complex climate change concepts. The research suggests that presenting scientific information through a familiar cultural lens contributed to making the topic less confusing and easier for the ākonga to grasp. This approach not only helped to improve their understanding but also enhanced the mana of ākonga Māori and their connection to the whenua (the land).

This research has several main implications. The findings provide evidence that incorporating Indigenous knowledge has wider educational benefits in climate change education, supporting the body of research that states what works well for ākonga Māori works well for all learners. The research also highlighted the importance of the concept of ako, literally meaning ‘to teach and learn,’ as the kaiako showed strength in being able to learn alongside ākonga. The thesis supports the use of Indigenous knowledge systems such as pūrākau alongside Western knowledge systems to develop holistic learning experiences. A recommendation from this thesis is to further explore the development of a climate change education model, relevant to the context of Aotearoa, which would centralise Indigenous knowledge. This could be modelled in the form of a waka hourua (double hulled ocean voyaging canoe) with the tohunga (knowledge holder and expert) on board signifying the use of Indigenous knowledge systems, with narratives such as pūrākau, playing a part in climate change education.

text: Weaving Mātauranga Māori into climate change education with primary school students in New Zealand This thesis explores the integration of Indigenous knowledge, specifically mātauranga Māori, into climate change education for primary school children in Aotearoa (New Zealand). It engages with pūrākau (verbal narratives that encode knowledge) gifted by the local hapū (Rangitāne sub-tribe) to a kura (school). The study contributes to the growing body of research that addresses a gap in research and teaching practice, which, despite global calls for action, remains inconsistent in teaching at this age level or lacks direct curriculum guidance in Aotearoa.

The main question for this study was: In what ways can Rangitāne pūrākau engage and further the understanding of Year five and six ākonga (learners) in learning about climate change within a kura in the lower North Island of Aotearoa?

This research used a mix of different research methods to explore this question. A learning intervention wove a pūrākau, climate change concepts and kai (food) together to create a ten-week learning programme. This learning intervention was then implemented by a kaiako (teacher) with a group of 21 Year five and six ākonga. Data were collected using pre- and post-tests to assess what students learned during the learning intervention, a group interview with the ākonga to hear their voices in the study, and an interview with their kaiako to gain insights into how engaged the ākonga were, their opinion on their understandings, and how aspects of the intervention went.

Analysis of the findings shows that the use of pūrākau and other forms of mātauranga Māori helped ākonga connect deeply with the material, which contributed positively to their engagement and to them gaining a sound understanding of complex climate change concepts. The research suggests that presenting scientific information through a familiar cultural lens contributed to making the topic less confusing and easier for the ākonga to grasp. This approach not only helped to improve their understanding but also enhanced the mana of ākonga Māori and their connection to the whenua (the land).

This research has several main implications. The findings provide evidence that incorporating Indigenous knowledge has wider educational benefits in climate change education, supporting the body of research that states what works well for ākonga Māori works well for all learners. The research also highlighted the importance of the concept of ako, literally meaning ‘to teach and learn,’ as the kaiako showed strength in being able to learn alongside ākonga. The thesis supports the use of Indigenous knowledge systems such as pūrākau alongside Western knowledge systems to develop holistic learning experiences. A recommendation from this thesis is to further explore the development of a climate change education model, relevant to the context of Aotearoa, which would centralise Indigenous knowledge. This could be modelled in the form of a waka hourua (double hulled ocean voyaging canoe) with the tohunga (knowledge holder and expert) on board signifying the use of Indigenous knowledge systems, with narratives such as pūrākau, playing a part in climate change education.

year: 2025