title: Effects of anthropogenic land use on temperate mangrove forests

authors: Thomson, Timothy

subjects: Temperate mangrove forests

abstract: Coastal ecosystems worldwide are facing unprecedented challenges due to ever increasing human activities, resulting in increased land-derived stressors that can threaten the health and integrity of these systems. Mangrove forests are unique ecosystems that play a crucial role in filtering nutrients, retaining pollutants, and sequestering carbon. However, to what extent they are impacted by an intensification of human pressures is unclear and empirical evidence of landscape scale effects of a holistic view of the ecosystem is scarce. This thesis investigates the effects of human land use on several aspects of temperate mangrove ecosystems and aims to identify potential vulnerabilities of ecosystem processes to provide a holistic view on the impacts that humas are having on these important ecosystems.
By working across a broad gradient of human land use, the first chapter establishes a connection between human land use intensity in catchments and regionally generalizable trends in mangrove forest structure and physicochemical parameters in sediments. Highlighting the integrated nature of anthropogenic impacts, this chapter emphasizes the need for holistic evaluations in assessing responses of complex natural systems to change.
The second chapter investigates environmental controls on organic matter degradation in mangrove forests. Results from this study emphasize the importance of considering multiple factors influencing degradation processes, that vary with the quality of the decaying organic matter. Furthermore, using the human land use gradient from the previous chapter, this study identifies an impact of human land use through eutrophication on the rate of labile organic matter loss from mangrove sediments.
The third chapter provides insights into bacterial communities in temperate mangrove sediments, revealing the persistent effects of nutrient enrichment even after the biochemical signal is lost. The study highlights the spatial resolution needed to detect impacts on microbial communities, warning that functional changes may persist beyond observable eutrophication effects.

The synthesis of these chapters provides a holistic view of the effects of anthropogenic impacts on temperate mangrove ecosystems across various scales. While some components of the system may benefit from moderate amounts of nutrient enrichment, others can deteriorate, ultimately diminishing overall service provisioning of the system. To understand and quantify these effects, this thesis calls for a nuanced understanding of disturbance effects on mangrove ecosystems, emphasizing their complexity and the interconnectedness of their components. It adds a valuable information about the functional resilience of mangrove forests in the face of human pressures and highlights the importance of an ecosystem-based perspective when assessing the effects of external stressors on these important ecosystems.

text: Effects of anthropogenic land use on temperate mangrove forests Coastal ecosystems worldwide are facing unprecedented challenges due to ever increasing human activities, resulting in increased land-derived stressors that can threaten the health and integrity of these systems. Mangrove forests are unique ecosystems that play a crucial role in filtering nutrients, retaining pollutants, and sequestering carbon. However, to what extent they are impacted by an intensification of human pressures is unclear and empirical evidence of landscape scale effects of a holistic view of the ecosystem is scarce. This thesis investigates the effects of human land use on several aspects of temperate mangrove ecosystems and aims to identify potential vulnerabilities of ecosystem processes to provide a holistic view on the impacts that humas are having on these important ecosystems.
By working across a broad gradient of human land use, the first chapter establishes a connection between human land use intensity in catchments and regionally generalizable trends in mangrove forest structure and physicochemical parameters in sediments. Highlighting the integrated nature of anthropogenic impacts, this chapter emphasizes the need for holistic evaluations in assessing responses of complex natural systems to change.
The second chapter investigates environmental controls on organic matter degradation in mangrove forests. Results from this study emphasize the importance of considering multiple factors influencing degradation processes, that vary with the quality of the decaying organic matter. Furthermore, using the human land use gradient from the previous chapter, this study identifies an impact of human land use through eutrophication on the rate of labile organic matter loss from mangrove sediments.
The third chapter provides insights into bacterial communities in temperate mangrove sediments, revealing the persistent effects of nutrient enrichment even after the biochemical signal is lost. The study highlights the spatial resolution needed to detect impacts on microbial communities, warning that functional changes may persist beyond observable eutrophication effects.

The synthesis of these chapters provides a holistic view of the effects of anthropogenic impacts on temperate mangrove ecosystems across various scales. While some components of the system may benefit from moderate amounts of nutrient enrichment, others can deteriorate, ultimately diminishing overall service provisioning of the system. To understand and quantify these effects, this thesis calls for a nuanced understanding of disturbance effects on mangrove ecosystems, emphasizing their complexity and the interconnectedness of their components. It adds a valuable information about the functional resilience of mangrove forests in the face of human pressures and highlights the importance of an ecosystem-based perspective when assessing the effects of external stressors on these important ecosystems.

year: 2024

title: Estimating pre-historic earthquake parameters in the Hamilton lowlands using laboratory geotechnical analyses of seismically liquefied volcanic-ash layers in lakes

authors: Chaneva, Jordanka

abstract: Soft-sediment deformation structures caused by pre-historic earthquakes were discovered in volcanicash (tephra) units preserved as discrete layers within soft, organic lake sediments in the Hamilton lowlands, North Island, New Zealand. Complementing a broader paleoliquefaction project that involves geological and seismological perspectives as well, this PhD research was focused on a geotechnical approach in analysing the paleoliquefaction features in the tephra layers across multiple 20 cal-ka-aged lakes in the Hamilton lowlands. Aiming to back-analyse pre-historic earthquakes that might have caused the palaeoliquefaction features, this thesis also had to address literature and knowledge gaps related to cyclic undrained behaviour and liquefaction resistance of pumiceous silts and sand-silt mixtures. Thus, the scope of this research covered the following objectives: (1) analyses of the geotechnical properties of the tephras of interest in order to define their liquefaction susceptibility, (2) investigation of the undrained monotonic and cyclic behaviour of a pumiceous silt (Tuhua silt, from lacustrine Tuhua tephra aged 7.6 cal ka) in order to fill knowledge gaps related to potential particle crushing affecting undrained cyclic behaviour as well as liquefaction resistance in pumiceous silts, (3) identification of the potential threshold of pumice content and/or fines content, at which pumiceous sand-silt mixtures (internal beds from lacustrine Mamaku tephra aged 8.0 cal ka) become crushable, and finally (4) developing a framework, that extends laboratory obtained liquefaction resistance ratios of three different beds of one of the tephras of interest, that provided enough volume for cyclic undrained triaxial testing (Mamaku tephra), into the rest of the tephras across the studied lakes (that only provided small volumes for sampling). The last objective assisted in reaching the main aim of this thesis which was to obtain the equivalent triggering earthquake parameters, i.e., peak ground acceleration, amax and earthquake magnitude, M for the tephras across the lakes, based on their estimated liquefaction resistances. It was found that the tephras in the lakes are pumiceous and liquefiable within the grain-size range: silts to sandy silts to silty sands. The results from undrained triaxial testing on the pumiceous silt showed that no particle crushing occurred and that the silty material behaved closer to the typical trends established for hard-grained soils than to those associated with pumiceous sands. Furthermore, the undrained cyclic triaxial testing program on three different beds, one silt and two silty sands, from one of the tephras of interest (Mamaku tephra), suggested a fines threshold below which begin to crush during cyclic triaxial testing to be somewhere between 31% and 20%. Empirical correlations used to estimate earthquake parameters from liquefaction resistance that are derived for hard-grained soils were, thus, considered reasonable for application to the pumiceous materials considered in the current study. The final results of this study showed that the tephra layers across the lakes were very sensitive and vulnerable to liquefaction at very low peak ground accelerations, i.e. amax ranging from 0.02 to 0.08 g within the range of magnitudes, M = 5 to 8.5. The high vulnerability to liquefaction across all the Mamaku tephra layers in the Hamilton lowlands (~13 lakes) was considered to be the result of the very low in-situ overburden stresses, consequence of their shallow burial depths in the lake environment, as well as the relatively low liquefaction resistance in situ. The results presented in this dissertation, (1) supply valuable information about the liquefaction potential of pre-historically liquefied tephra layers, assisting local paleoliquefaction studies in the Hamilton lowlands area, (2) explore the possibility of applying laboratory-based liquefaction resistance analysis in paleoliquefaction studies, and (3) contribute to better understanding of the undrained behaviour and liquefaction resistance of pumiceous sand-silt mixtures.

text: Estimating pre-historic earthquake parameters in the Hamilton lowlands using laboratory geotechnical analyses of seismically liquefied volcanic-ash layers in lakes Soft-sediment deformation structures caused by pre-historic earthquakes were discovered in volcanicash (tephra) units preserved as discrete layers within soft, organic lake sediments in the Hamilton lowlands, North Island, New Zealand. Complementing a broader paleoliquefaction project that involves geological and seismological perspectives as well, this PhD research was focused on a geotechnical approach in analysing the paleoliquefaction features in the tephra layers across multiple 20 cal-ka-aged lakes in the Hamilton lowlands. Aiming to back-analyse pre-historic earthquakes that might have caused the palaeoliquefaction features, this thesis also had to address literature and knowledge gaps related to cyclic undrained behaviour and liquefaction resistance of pumiceous silts and sand-silt mixtures. Thus, the scope of this research covered the following objectives: (1) analyses of the geotechnical properties of the tephras of interest in order to define their liquefaction susceptibility, (2) investigation of the undrained monotonic and cyclic behaviour of a pumiceous silt (Tuhua silt, from lacustrine Tuhua tephra aged 7.6 cal ka) in order to fill knowledge gaps related to potential particle crushing affecting undrained cyclic behaviour as well as liquefaction resistance in pumiceous silts, (3) identification of the potential threshold of pumice content and/or fines content, at which pumiceous sand-silt mixtures (internal beds from lacustrine Mamaku tephra aged 8.0 cal ka) become crushable, and finally (4) developing a framework, that extends laboratory obtained liquefaction resistance ratios of three different beds of one of the tephras of interest, that provided enough volume for cyclic undrained triaxial testing (Mamaku tephra), into the rest of the tephras across the studied lakes (that only provided small volumes for sampling). The last objective assisted in reaching the main aim of this thesis which was to obtain the equivalent triggering earthquake parameters, i.e., peak ground acceleration, amax and earthquake magnitude, M for the tephras across the lakes, based on their estimated liquefaction resistances. It was found that the tephras in the lakes are pumiceous and liquefiable within the grain-size range: silts to sandy silts to silty sands. The results from undrained triaxial testing on the pumiceous silt showed that no particle crushing occurred and that the silty material behaved closer to the typical trends established for hard-grained soils than to those associated with pumiceous sands. Furthermore, the undrained cyclic triaxial testing program on three different beds, one silt and two silty sands, from one of the tephras of interest (Mamaku tephra), suggested a fines threshold below which begin to crush during cyclic triaxial testing to be somewhere between 31% and 20%. Empirical correlations used to estimate earthquake parameters from liquefaction resistance that are derived for hard-grained soils were, thus, considered reasonable for application to the pumiceous materials considered in the current study. The final results of this study showed that the tephra layers across the lakes were very sensitive and vulnerable to liquefaction at very low peak ground accelerations, i.e. amax ranging from 0.02 to 0.08 g within the range of magnitudes, M = 5 to 8.5. The high vulnerability to liquefaction across all the Mamaku tephra layers in the Hamilton lowlands (~13 lakes) was considered to be the result of the very low in-situ overburden stresses, consequence of their shallow burial depths in the lake environment, as well as the relatively low liquefaction resistance in situ. The results presented in this dissertation, (1) supply valuable information about the liquefaction potential of pre-historically liquefied tephra layers, assisting local paleoliquefaction studies in the Hamilton lowlands area, (2) explore the possibility of applying laboratory-based liquefaction resistance analysis in paleoliquefaction studies, and (3) contribute to better understanding of the undrained behaviour and liquefaction resistance of pumiceous sand-silt mixtures.

year: 2024

title: Tapuwaekiwi tapuaeharuru taiharuru te Whakatōhea toheraoa: Connecting to my iwi and reclamation of identity through endurance running grounded in iwi narratives and tikanga/culture.

authors: Helyar-Magill, Nicholas

abstract: This thesis explores the intersection of endurance, whakapapa, and cultural reconnection through the lens of ultra-marathon running and Te Whakatōhea tīpuna pūrākau. By weaving together personal narratives, historical contexts, and contemporary athletic practices, this research examines the role of endurance sports as a pathway for cultural revitalisation and identity reclamation among Māori athletes.
Endurance is a fundamental characteristic of Te Whakatōhea, embodied not only in the physical feats of long-distance running but also in the iwi's historical resilience through colonisation, raupatu, and cultural disconnection. This research positions ultra-marathon running as both a metaphor and a mechanism for reclaiming whakapapa, fostering well-being, and strengthening the connection between Māori athletes and te ao Māori. Drawing upon Kaupapa Māori methodology, qualitative research methods, and tikanga Māori principles, this research seeks to decolonise endurance sports by embedding iwi narratives, tikanga, and mana whenua engagement into the sport of ultra-running.
A central aim of this research is to develop a culturally grounded framework that integrates Te Whakatōhea pūrākau and tikanga into ultra-marathon events. This framework envisions a race that traverses ancestral pathways, acknowledges the whenua and mana whenua, and fosters a culturally safe environment for Māori athletes. The research questions driving this thesis examine the historical endurance of Te Whakatōhea, the impact of colonisation on Māori participation in endurance sports, and the potential for tikanga to be embedded in ultra-marathon events.
The findings of this research reveal that endurance is deeply woven into the whakapapa of Te Whakatōhea and that ultra-marathon running serves as a powerful means of reconnecting with iwi identity, whenua, and te ao Māori. Through interviews with Māori endurance athletes and an exploration of iwi narratives, this research highlights the transformative potential of culturally embedded endurance sports. Furthermore, the research identifies barriers to Māori participation in ultra-marathons, including historical disenfranchisement from traditional athletic spaces and the predominance of Pākehā worldviews in endurance sports. Addressing these barriers, this thesis proposes a tikanga-based model that seeks to attract greater Māori
participation by integrating kaupapa Māori principles into the design, organisation, and execution of ultra-marathon events.
This research is also a personal journey of endurance and reconnection, reflecting on my own whakapapa as a descendant of Te Whakatōhea and an ultra-marathon runner. Raised outside of the iwi rohe, my path of reclaiming identity through sport mirrors the broader themes of cultural endurance and revitalisation explored in this thesis. By engaging with iwi histories, participating in kaupapa Māori spaces, and embedding tikanga into my athletic practice, I have sought to bridge the gap between past and present, creating a future where Māori endurance athletes can thrive within a culturally affirming space.
Ultimately, this thesis contributes to the growing discourse on Indigenous endurance sports, cultural resilience, and decolonial approaches to athletic participation. It affirms that ultra-marathon running, when grounded in whakapapa and tikanga, has the potential to serve as a tool for cultural reconnection, healing, and identity reclamation for Māori athletes and Te Whakatōhea whānau.

text: Tapuwaekiwi tapuaeharuru taiharuru te Whakatōhea toheraoa: Connecting to my iwi and reclamation of identity through endurance running grounded in iwi narratives and tikanga/culture. This thesis explores the intersection of endurance, whakapapa, and cultural reconnection through the lens of ultra-marathon running and Te Whakatōhea tīpuna pūrākau. By weaving together personal narratives, historical contexts, and contemporary athletic practices, this research examines the role of endurance sports as a pathway for cultural revitalisation and identity reclamation among Māori athletes.
Endurance is a fundamental characteristic of Te Whakatōhea, embodied not only in the physical feats of long-distance running but also in the iwi's historical resilience through colonisation, raupatu, and cultural disconnection. This research positions ultra-marathon running as both a metaphor and a mechanism for reclaiming whakapapa, fostering well-being, and strengthening the connection between Māori athletes and te ao Māori. Drawing upon Kaupapa Māori methodology, qualitative research methods, and tikanga Māori principles, this research seeks to decolonise endurance sports by embedding iwi narratives, tikanga, and mana whenua engagement into the sport of ultra-running.
A central aim of this research is to develop a culturally grounded framework that integrates Te Whakatōhea pūrākau and tikanga into ultra-marathon events. This framework envisions a race that traverses ancestral pathways, acknowledges the whenua and mana whenua, and fosters a culturally safe environment for Māori athletes. The research questions driving this thesis examine the historical endurance of Te Whakatōhea, the impact of colonisation on Māori participation in endurance sports, and the potential for tikanga to be embedded in ultra-marathon events.
The findings of this research reveal that endurance is deeply woven into the whakapapa of Te Whakatōhea and that ultra-marathon running serves as a powerful means of reconnecting with iwi identity, whenua, and te ao Māori. Through interviews with Māori endurance athletes and an exploration of iwi narratives, this research highlights the transformative potential of culturally embedded endurance sports. Furthermore, the research identifies barriers to Māori participation in ultra-marathons, including historical disenfranchisement from traditional athletic spaces and the predominance of Pākehā worldviews in endurance sports. Addressing these barriers, this thesis proposes a tikanga-based model that seeks to attract greater Māori
participation by integrating kaupapa Māori principles into the design, organisation, and execution of ultra-marathon events.
This research is also a personal journey of endurance and reconnection, reflecting on my own whakapapa as a descendant of Te Whakatōhea and an ultra-marathon runner. Raised outside of the iwi rohe, my path of reclaiming identity through sport mirrors the broader themes of cultural endurance and revitalisation explored in this thesis. By engaging with iwi histories, participating in kaupapa Māori spaces, and embedding tikanga into my athletic practice, I have sought to bridge the gap between past and present, creating a future where Māori endurance athletes can thrive within a culturally affirming space.
Ultimately, this thesis contributes to the growing discourse on Indigenous endurance sports, cultural resilience, and decolonial approaches to athletic participation. It affirms that ultra-marathon running, when grounded in whakapapa and tikanga, has the potential to serve as a tool for cultural reconnection, healing, and identity reclamation for Māori athletes and Te Whakatōhea whānau.

year: 2024