title: Colonization dynamics and facilitative impacts of nitrogen-fixing shrub in primary succession

authors: Walker, Lawrence R.

subjects: Coriaria arborea

abstract: Whether nitrogen-fixing plants facilitate or inhibit species change in primary succession is best resolved by examining their impacts throughout the plant's entire life cycle from arrival to senescence. We experimentally examined two aspects of the successional impacts of a nitrogen-fixing shrub, Coriaria arborea, on Mt. Tarawera, a volcano in New Zealand: factors limiting Coriaria colonization and impacts of Coriaria-induced soil changes on a later successional tree, Griselinia littoralis. Coriaria germination was promoted by artificial wind protection and by the presence of heath shrubs. Transplanted Coriaria seedlings survived only if nodulated with Frankia, and the addition of Coriaria-enriched soils slowed Coriaria seedling growth and did not improve seedling survival. This explained why Coriaria seedlings were found mostly in protected habitats away from adult Coriaria, and suggested that Coriaria thickets are not self-replacing. Coriaria increased soil fertility by developing a 4 cm thick organic soil horizon that was richer in nitrogen (tenfold) and phosphorus (threefold) than pre-Coriaria stages. These soil changes resulted in three- to sixfold increases in growth of Griselinia when it was grown in Coriaria-enriched soils in a glasshouse. Coriaria's net effect on primary succession is facilitative, but the establishment of Coriaria is itself facilitated by the amelioration of the physical habitat by earlier colonists, suggesting facilitation is important throughout the life cycle of Coriaria. Sequential facilitative events determine the order of species replacements in this study but inhibition, linked to the developmental stages of Coriaria, may determine.

text: Colonization dynamics and facilitative impacts of nitrogen-fixing shrub in primary succession Whether nitrogen-fixing plants facilitate or inhibit species change in primary succession is best resolved by examining their impacts throughout the plant's entire life cycle from arrival to senescence. We experimentally examined two aspects of the successional impacts of a nitrogen-fixing shrub, Coriaria arborea, on Mt. Tarawera, a volcano in New Zealand: factors limiting Coriaria colonization and impacts of Coriaria-induced soil changes on a later successional tree, Griselinia littoralis. Coriaria germination was promoted by artificial wind protection and by the presence of heath shrubs. Transplanted Coriaria seedlings survived only if nodulated with Frankia, and the addition of Coriaria-enriched soils slowed Coriaria seedling growth and did not improve seedling survival. This explained why Coriaria seedlings were found mostly in protected habitats away from adult Coriaria, and suggested that Coriaria thickets are not self-replacing. Coriaria increased soil fertility by developing a 4 cm thick organic soil horizon that was richer in nitrogen (tenfold) and phosphorus (threefold) than pre-Coriaria stages. These soil changes resulted in three- to sixfold increases in growth of Griselinia when it was grown in Coriaria-enriched soils in a glasshouse. Coriaria's net effect on primary succession is facilitative, but the establishment of Coriaria is itself facilitated by the amelioration of the physical habitat by earlier colonists, suggesting facilitation is important throughout the life cycle of Coriaria. Sequential facilitative events determine the order of species replacements in this study but inhibition, linked to the developmental stages of Coriaria, may determine.

year: 2003-04

title: Two-state systems with non-Markovian thermal and squeezed quantum noise inputs

authors: Parkins, Andrew Scott

abstract: The effect of quantum noise on the two-state system is studied in the context of (i) coherent quantum tunnelling in a double-well system subject to low temperature quantum noise, and (ii) the two-level atom subject to finite bandwidth squeezed noise. Our approach to these problems is based on the adjoint equation, which describes the evolution of a quantum stochastic density operator. This equation is amenable to solution by ordinary stochastic methods, of which numerical simulation plays the most significant role in our calculations.
The dissipative double-well system is relevant to the search for macroscopic quantum coherence in superconducting quantum interference devices, and previous work, starting from a two-state model and using path integral methods, has established the so-called “noninteracting-blip approximation” as a central result. The adjoint equation, applied to this problem in the weak coupling limit, is shown to closely reproduce this result. The noninteracting-blip approximation entails a Markovian-type assumption about the noise, and, by means of stochastic simulation, we are able to check, and confirm, the validity of this assumption, even for the case of a zero-temperature bath.
Squeezed light, which has reduced quantum fluctuations in one quadrature phase, has been produced experimentally, and possible applications are under active consideration. Analyses of the effect of squeezed light on fundamental radiative processes in simple atoms have revealed interesting possibilities, most notably line-narrowing in the fluorescence spectrum. The original analyses in this field of research have been based on the assumption of broad bandwidth squeezing, and we review the primary results found in this limit. Also in this limit, we study in more detail the phenomenon of squeezed-light-induced photon echoes.
For broad bandwidth squeezing, line-narrowing in resonance fluorescence is restricted to the central fluorescence peak, while the Rabi sidebands exhibit broadening. We examine strongly driven resonance fluorescence for the case in which squeezing is confined to relatively small regions of frequency space about individual fluorescence peaks. It is shown that the noisy component associated with the unsqueezed quadrature phase can be effectively decoupled from the atomic dynamics, which allows narrowing to occur in all three peaks of the spectrum.
Finally, we address the practical problem of producing an effective coupling between an atom and a realistic three-dimensional squeezed field of modest angular spread. We show that this can be achieved, in principle, inside a microscopic plane mirror cavity, provided the injected squeezed field is suitably mode-matched to the cavity.

text: Two-state systems with non-Markovian thermal and squeezed quantum noise inputs The effect of quantum noise on the two-state system is studied in the context of (i) coherent quantum tunnelling in a double-well system subject to low temperature quantum noise, and (ii) the two-level atom subject to finite bandwidth squeezed noise. Our approach to these problems is based on the adjoint equation, which describes the evolution of a quantum stochastic density operator. This equation is amenable to solution by ordinary stochastic methods, of which numerical simulation plays the most significant role in our calculations.
The dissipative double-well system is relevant to the search for macroscopic quantum coherence in superconducting quantum interference devices, and previous work, starting from a two-state model and using path integral methods, has established the so-called “noninteracting-blip approximation” as a central result. The adjoint equation, applied to this problem in the weak coupling limit, is shown to closely reproduce this result. The noninteracting-blip approximation entails a Markovian-type assumption about the noise, and, by means of stochastic simulation, we are able to check, and confirm, the validity of this assumption, even for the case of a zero-temperature bath.
Squeezed light, which has reduced quantum fluctuations in one quadrature phase, has been produced experimentally, and possible applications are under active consideration. Analyses of the effect of squeezed light on fundamental radiative processes in simple atoms have revealed interesting possibilities, most notably line-narrowing in the fluorescence spectrum. The original analyses in this field of research have been based on the assumption of broad bandwidth squeezing, and we review the primary results found in this limit. Also in this limit, we study in more detail the phenomenon of squeezed-light-induced photon echoes.
For broad bandwidth squeezing, line-narrowing in resonance fluorescence is restricted to the central fluorescence peak, while the Rabi sidebands exhibit broadening. We examine strongly driven resonance fluorescence for the case in which squeezing is confined to relatively small regions of frequency space about individual fluorescence peaks. It is shown that the noisy component associated with the unsqueezed quadrature phase can be effectively decoupled from the atomic dynamics, which allows narrowing to occur in all three peaks of the spectrum.
Finally, we address the practical problem of producing an effective coupling between an atom and a realistic three-dimensional squeezed field of modest angular spread. We show that this can be achieved, in principle, inside a microscopic plane mirror cavity, provided the injected squeezed field is suitably mode-matched to the cavity.

year: 1990

title: Ka pūhia te puna o te kauae runga, kia pūheke ai ngā wai ki te kauae raro: Investigating the inclusion of Māori in engineering - A Māori engineers’ journey

authors: Poli, Teresa

subjects: Engineering

abstract: This thesis explored views held by Māori and non- Māori regarding te ao Māori across the engineering system of education, academia, and industry, in understanding what challenges and experiences Māori engineers may face. 
While there are incremental and progressive changes beginning to be seen in the engineering industry when working with iwi Māori, the history of engineering itself is intertwined with colonial contributions that have oppressed Māori. These historical influences continue to impact Māori today as they navigate educational pathways and enter the engineering profession. Colonisation, with its consequences such as stealing te reo, and various forms of cultural oppression, has led to Māori feeling disconnected from the engineering profession. It has also resulted in invisible cultural labour being placed on Māori, as we transition into a profession attempting to rectify the historic wrongs of the past. It was realised a gap existed in engineering education, failing to adequately equip graduates with the essential skills needed for success as engineers in Aotearoa. This gap was particularly evident in the cultural skills necessary for effective collaboration with clients, as well as for working harmoniously with Māori colleagues.
The research framework employed in this rangahau was He waka hourua, symbolising the journey towards a vision where Māori not only hold mana but also a sense of belonging in the field of engineering. This framework recognises the importance of both Māori and Pākehā voices, with a preference for Māori engineers taking a leading role in steering the direction towards the envisioned destination. The data collection process involved the use of Surveys and Whakawhiti kōrero methodologies, gathering both quantitative and qualitative information that played a crucial role in shaping the research findings.
Woven throughout this rangahau are the personal experiences shared by the author, and her journey as a wahine Māori engineer through the engineering system, anchored by her Māoritanga. Throughout, this rangahau analogies of waka are utilised as an acknowledgement of the great engineering feats developed by Māori, and paying homage to the idea that Māori have always been engineers, drawing from characteristics and traits passed down from atua and tīpuna.
The author highlights the scarcity of literature dedicated to supporting the kaupapa of enhancing the mana of Māori in engineering. Rather than providing definitive answers to address the challenges that diminish Māori mana in engineering, this thesis serves as a foundational point, anchored at the wharf, for future rangatira to continue the voyage. Enhancing the mana of Māori in engineering presents an enduring wero, but there is optimism for the future of Māori in engineering, as we carve out institutionalism, we begin to make space on our waka.

text: Ka pūhia te puna o te kauae runga, kia pūheke ai ngā wai ki te kauae raro: Investigating the inclusion of Māori in engineering - A Māori engineers’ journey This thesis explored views held by Māori and non- Māori regarding te ao Māori across the engineering system of education, academia, and industry, in understanding what challenges and experiences Māori engineers may face. 
While there are incremental and progressive changes beginning to be seen in the engineering industry when working with iwi Māori, the history of engineering itself is intertwined with colonial contributions that have oppressed Māori. These historical influences continue to impact Māori today as they navigate educational pathways and enter the engineering profession. Colonisation, with its consequences such as stealing te reo, and various forms of cultural oppression, has led to Māori feeling disconnected from the engineering profession. It has also resulted in invisible cultural labour being placed on Māori, as we transition into a profession attempting to rectify the historic wrongs of the past. It was realised a gap existed in engineering education, failing to adequately equip graduates with the essential skills needed for success as engineers in Aotearoa. This gap was particularly evident in the cultural skills necessary for effective collaboration with clients, as well as for working harmoniously with Māori colleagues.
The research framework employed in this rangahau was He waka hourua, symbolising the journey towards a vision where Māori not only hold mana but also a sense of belonging in the field of engineering. This framework recognises the importance of both Māori and Pākehā voices, with a preference for Māori engineers taking a leading role in steering the direction towards the envisioned destination. The data collection process involved the use of Surveys and Whakawhiti kōrero methodologies, gathering both quantitative and qualitative information that played a crucial role in shaping the research findings.
Woven throughout this rangahau are the personal experiences shared by the author, and her journey as a wahine Māori engineer through the engineering system, anchored by her Māoritanga. Throughout, this rangahau analogies of waka are utilised as an acknowledgement of the great engineering feats developed by Māori, and paying homage to the idea that Māori have always been engineers, drawing from characteristics and traits passed down from atua and tīpuna.
The author highlights the scarcity of literature dedicated to supporting the kaupapa of enhancing the mana of Māori in engineering. Rather than providing definitive answers to address the challenges that diminish Māori mana in engineering, this thesis serves as a foundational point, anchored at the wharf, for future rangatira to continue the voyage. Enhancing the mana of Māori in engineering presents an enduring wero, but there is optimism for the future of Māori in engineering, as we carve out institutionalism, we begin to make space on our waka.

year: 2024