title: Photosynthesis and transpiration in a dry-land Pinus radiata forest

authors: Walcroft, Adrian S.

abstract: This thesis investigates biotic and abiotic regulation of photosynthesis and transpiration at the leaf and canopy scales in a dry-land Pinus radiata D. Don forest by combining gas exchange measurements with biophysical process-based models of photosynthesis, radiation transfer, and soil water balance.

Responses of photosynthesis to leaf intercellular CO₂ concentration in two-year old P. radiata seedlings were measured at a range of temperatures and leaf nitrogen concentrations in order to quantify parameters describing photosynthetic capacity and temperature response in a biophysical model of C₃ photosynthesis. Increasing leaf temperature from 8 °C to 30 °C caused a four-fold increase in Vcₘₐₓ the maximum rate of carboxylation (10.7 to 43.3 μmol m⁻² s⁻¹), and a three-fold increase in Jₘₐₓ, the maximum electron transport rate (20.5 to 60.2 μmol m⁻² s⁻¹). Foliar nitrogen concentration (N) varied between 0.36 mmol g⁻¹ and 1.27 mmol g⁻¹, and there were linear relationships between N and both Vcₘₐₓ and Jₘₐₓ. Measurements made throughout the crown of a forest tree, where N varied from 0.83 mmol g⁻¹ near the base to 1.54 mmol g⁻¹ near the leader, yielded similar relationships.

The leaf-level photosynthesis model was combined with a water balance model to successfully explain a seasonal pattern in stable carbon isotope composition (δ¹³C) measured within annual rings of P. radiata from two sites which differed markedly in annual water balance. Over two growing seasons there was good agreement between mean canopy-level cᵢ derived from the tree-ring δ¹³C data and modelled leaf-level cᵢ levels. The amplitudes of seasonal δ¹³C variation at the wet and dry sites were 1-2 %₀ and 4 %₀ respectively, and mean δ¹³C values from the wet site were 3 %₀ more ¹³C depleted than those from the dry site implying lower water-use efficiency (carbon assimilation per unit transpiration). Seasonal variation in carbon isotope discrimination of leaves in the canopy is therefore reflected directly in the δ¹³C of stem wood.

A canopy photosynthesis model was developed by combining the leaf-level model with a model of canopy radiation transfer, and used as a framework to analyse a field experiment designed to quantify the response of photosynthesis and tree growth to a long-term reduction in illuminated leaf area. Shading the lower crown of two young forest trees reduced absorbed radiation and canopy photosynthesis by 11 and 9 % respectively in the first year. Nitrogen was translocated from current year foliage below the shade cloth to that above, and carbon partitioning to the branches increased at the expense of stem growth. In the second year, the effect of the shading on absorbed radiation, canopy photosynthesis and tree growth was less due to a reduction in shaded foliage proportional to total leaf area. Additionally, a prolonged period of soil water deficit during the summer of year 2 reduced photosynthesis, stomatal conductance and growth similarly in both shaded and control trees. Models which scale up processes from the leaf-level to the canopy can provide a framework to analyse and interpret field experiments.

text: Photosynthesis and transpiration in a dry-land Pinus radiata forest This thesis investigates biotic and abiotic regulation of photosynthesis and transpiration at the leaf and canopy scales in a dry-land Pinus radiata D. Don forest by combining gas exchange measurements with biophysical process-based models of photosynthesis, radiation transfer, and soil water balance.

Responses of photosynthesis to leaf intercellular CO₂ concentration in two-year old P. radiata seedlings were measured at a range of temperatures and leaf nitrogen concentrations in order to quantify parameters describing photosynthetic capacity and temperature response in a biophysical model of C₃ photosynthesis. Increasing leaf temperature from 8 °C to 30 °C caused a four-fold increase in Vcₘₐₓ the maximum rate of carboxylation (10.7 to 43.3 μmol m⁻² s⁻¹), and a three-fold increase in Jₘₐₓ, the maximum electron transport rate (20.5 to 60.2 μmol m⁻² s⁻¹). Foliar nitrogen concentration (N) varied between 0.36 mmol g⁻¹ and 1.27 mmol g⁻¹, and there were linear relationships between N and both Vcₘₐₓ and Jₘₐₓ. Measurements made throughout the crown of a forest tree, where N varied from 0.83 mmol g⁻¹ near the base to 1.54 mmol g⁻¹ near the leader, yielded similar relationships.

The leaf-level photosynthesis model was combined with a water balance model to successfully explain a seasonal pattern in stable carbon isotope composition (δ¹³C) measured within annual rings of P. radiata from two sites which differed markedly in annual water balance. Over two growing seasons there was good agreement between mean canopy-level cᵢ derived from the tree-ring δ¹³C data and modelled leaf-level cᵢ levels. The amplitudes of seasonal δ¹³C variation at the wet and dry sites were 1-2 %₀ and 4 %₀ respectively, and mean δ¹³C values from the wet site were 3 %₀ more ¹³C depleted than those from the dry site implying lower water-use efficiency (carbon assimilation per unit transpiration). Seasonal variation in carbon isotope discrimination of leaves in the canopy is therefore reflected directly in the δ¹³C of stem wood.

A canopy photosynthesis model was developed by combining the leaf-level model with a model of canopy radiation transfer, and used as a framework to analyse a field experiment designed to quantify the response of photosynthesis and tree growth to a long-term reduction in illuminated leaf area. Shading the lower crown of two young forest trees reduced absorbed radiation and canopy photosynthesis by 11 and 9 % respectively in the first year. Nitrogen was translocated from current year foliage below the shade cloth to that above, and carbon partitioning to the branches increased at the expense of stem growth. In the second year, the effect of the shading on absorbed radiation, canopy photosynthesis and tree growth was less due to a reduction in shaded foliage proportional to total leaf area. Additionally, a prolonged period of soil water deficit during the summer of year 2 reduced photosynthesis, stomatal conductance and growth similarly in both shaded and control trees. Models which scale up processes from the leaf-level to the canopy can provide a framework to analyse and interpret field experiments.

year: 1998

title: Open-source tool for heat exchanger network synthesis

authors: Hall, Keegan

abstract: The synthesis of heat exchanger networks (HEN) is not a trivial task due to the mixed integer and non-linear nature of the optimisation problem, yet it can provide significant cost and energy use savings to an industrial processing site. Many HEN synthesis models are developed using propriety solvers, which make it difficult for industrial companies to realise the potential of optimisation. This paper introduces a new open-source tool for HEN synthesis built in Python using the GEKKO library, which interfaces with the solver APOPT. The tool features three different synthesis methods, two of which utilise a two-step method where step one aims to initialise or narrow the search space prior to global optimisation in the second synthesis step. A unique feature of this work compared to previous HEN synthesis studies is the application of a true driving force constraint, dQ/dA, (instead of the conventional, but at times crude, minimum approach temperature, ∆Tmin) to provide feasible initial variable values to the second step. To demonstrate the current progress in developing the open-source tool, network solutions obtained by the tool were purposefully compared with the best reported solutions for three common case studies in HEN synthesis literature. For a small problem, the tool achieved a solution within 0.02 % of the best literature solution and attained a solution for the two larger problems within 4 % and 21% of the best literature solution. Before the tool can be made publicly available, further work is needed to implement a non-isothermal mixing model across stream splits, which is expected to yield a more optimal HEN.

text: Open-source tool for heat exchanger network synthesis The synthesis of heat exchanger networks (HEN) is not a trivial task due to the mixed integer and non-linear nature of the optimisation problem, yet it can provide significant cost and energy use savings to an industrial processing site. Many HEN synthesis models are developed using propriety solvers, which make it difficult for industrial companies to realise the potential of optimisation. This paper introduces a new open-source tool for HEN synthesis built in Python using the GEKKO library, which interfaces with the solver APOPT. The tool features three different synthesis methods, two of which utilise a two-step method where step one aims to initialise or narrow the search space prior to global optimisation in the second synthesis step. A unique feature of this work compared to previous HEN synthesis studies is the application of a true driving force constraint, dQ/dA, (instead of the conventional, but at times crude, minimum approach temperature, ∆Tmin) to provide feasible initial variable values to the second step. To demonstrate the current progress in developing the open-source tool, network solutions obtained by the tool were purposefully compared with the best reported solutions for three common case studies in HEN synthesis literature. For a small problem, the tool achieved a solution within 0.02 % of the best literature solution and attained a solution for the two larger problems within 4 % and 21% of the best literature solution. Before the tool can be made publicly available, further work is needed to implement a non-isothermal mixing model across stream splits, which is expected to yield a more optimal HEN.

year: 2022-09-05

title: Listening at dawn: Trans* storywork for all my relations

authors: Luna-Pizano, Rafaela

subjects: Transgender

abstract: This is a love letter to trans* people: a reminder of our place and legacy of trans*formation. In the form of collaborative and ceremonial research, this PhD with creative practice component is an affirmation of embodied, elemental storytelling as a necessary practice for unearthing and grounding the traditional knowledge that Indigenous-Trans* (Indigi-Trans*) people carry within our body-spirits. This creative practice (co)research uplifts liminal states of being, as given to us by our elemental ancestors, in the decolonial project of Indigenous (encompassing Black and Trans*) body-land reclamation and restoration. By recognizing and nourishing the power of the between, this thesis remembers practices of place that are rooted in the body, often our last piece of ancestral land as displaced and diasporic Indigi-Trans* people. Spanning the coasts of Aotearoa-NZ to the west coast of Ixtlán (Turtle Island-US), this creative project listened to the somatic presence of Indigi-Trans* creators (co-researchers) who are in varying states of connection to their ancestral lands and traditions. To account for sudden and extreme shifts in safety and access due to the COVID-19 pandemic, I created online and on-site rituals to sustain connection and retrace our ancestors’ techniques of time and space travel. By engaging with body-awareness practices or ritual performances offered in this project, co-researchers and storytellers were able to experiment with ‘knew’ ways of engaging the ancestral power of place. As a member of the communities contributing to this project, I witnessed an important transformation within co-researchers from a sense of landlessness to a sense of infinite place. This transformation gave co-researchers and storytellers a new source of power, strengthening their spiritual-mental capacity to receive and grow (especially during the height of the COVID-19 pandemic). In a political climate of increasing backlash to trans* and Indigenous sovereignty, this creative project is a unique contribution to the kete, or basket of knowledge that we offer to the coming generations of trans*formational practitioners and scholars.
Situated within the realms of Indigenous, Queer, Xicana and Critical Black Trans* Feminist theories, this creative project also draws upon performance, sound, and poetic practice to hatch another creative methodology that centers place-based ritual. As I created this thesis in a liminal waterscape, crossing back and forth between Aotearoa and Ixtlán, colliding with the onset of the COVID-19 pandemic, I opened myself to theories generated by the lands that nourished me. Thus, a Kaupapa Māori and Mana Wahine informed approach emerges as the prow of this banka, or canoe that carries other Black, Indigenous and Trans* lineages of scholarship. From this fluid place of theory, my practice as an Indigi-
Trans* ritualist, poet, and sound artist grounds these theories in my body and the body-lands of my co-researchers. Together, we create a Kappi (Ilocano crab motif referencing Maui’s fishing up of our islands) methodology, or the underwater reflections of celestial movement as mapped by Indigi-Trans* freedom strategies. As the co-researchers and storytellers of this project demonstrate, many Indigi-Trans* people are (re)birthing and (re)creating life and possibility just by existing. Our power of place, in body and land, can link and strengthen all Indigenous sovereignty movements when our communities take up the call to foster each person’s fluid potential.
Although this entire project is creative, as a PhD with creative practice component, this project is an ebb and flow of written and other media components. Most of the ‘creative component’ occurred during the co-research stage of this thesis and has been documented via photographs, video, participant testimony, soundscapes, and poetry on a separate, companion website (https://transjoy.cargo.site/). These artifacts of ritual research are also discussed within the harvest (data) section of the written portion, but reader/listeners are encouraged to view the website in tandem. Poetry, narrative, and soundscapes (hyperlinks or bone icons) weave throughout the written portion to create a multi-sensory experience that privileges my roots in aural tradition. Together, the performances, website, poetry, and soundscapes constitute roughly thirty percent of the final thesis, weighing more heavily on a written portion of seventy percent. Listener/readers are encouraged to experience the written and multi-media portions in tandem, cycling back and forth in a playful spirit as the next step of creative practice: listener participation. Please enter this project with the care and excitement invited of all listeners when the storyteller asks, “are you ready to hear a story?”

text: Listening at dawn: Trans* storywork for all my relations This is a love letter to trans* people: a reminder of our place and legacy of trans*formation. In the form of collaborative and ceremonial research, this PhD with creative practice component is an affirmation of embodied, elemental storytelling as a necessary practice for unearthing and grounding the traditional knowledge that Indigenous-Trans* (Indigi-Trans*) people carry within our body-spirits. This creative practice (co)research uplifts liminal states of being, as given to us by our elemental ancestors, in the decolonial project of Indigenous (encompassing Black and Trans*) body-land reclamation and restoration. By recognizing and nourishing the power of the between, this thesis remembers practices of place that are rooted in the body, often our last piece of ancestral land as displaced and diasporic Indigi-Trans* people. Spanning the coasts of Aotearoa-NZ to the west coast of Ixtlán (Turtle Island-US), this creative project listened to the somatic presence of Indigi-Trans* creators (co-researchers) who are in varying states of connection to their ancestral lands and traditions. To account for sudden and extreme shifts in safety and access due to the COVID-19 pandemic, I created online and on-site rituals to sustain connection and retrace our ancestors’ techniques of time and space travel. By engaging with body-awareness practices or ritual performances offered in this project, co-researchers and storytellers were able to experiment with ‘knew’ ways of engaging the ancestral power of place. As a member of the communities contributing to this project, I witnessed an important transformation within co-researchers from a sense of landlessness to a sense of infinite place. This transformation gave co-researchers and storytellers a new source of power, strengthening their spiritual-mental capacity to receive and grow (especially during the height of the COVID-19 pandemic). In a political climate of increasing backlash to trans* and Indigenous sovereignty, this creative project is a unique contribution to the kete, or basket of knowledge that we offer to the coming generations of trans*formational practitioners and scholars.
Situated within the realms of Indigenous, Queer, Xicana and Critical Black Trans* Feminist theories, this creative project also draws upon performance, sound, and poetic practice to hatch another creative methodology that centers place-based ritual. As I created this thesis in a liminal waterscape, crossing back and forth between Aotearoa and Ixtlán, colliding with the onset of the COVID-19 pandemic, I opened myself to theories generated by the lands that nourished me. Thus, a Kaupapa Māori and Mana Wahine informed approach emerges as the prow of this banka, or canoe that carries other Black, Indigenous and Trans* lineages of scholarship. From this fluid place of theory, my practice as an Indigi-
Trans* ritualist, poet, and sound artist grounds these theories in my body and the body-lands of my co-researchers. Together, we create a Kappi (Ilocano crab motif referencing Maui’s fishing up of our islands) methodology, or the underwater reflections of celestial movement as mapped by Indigi-Trans* freedom strategies. As the co-researchers and storytellers of this project demonstrate, many Indigi-Trans* people are (re)birthing and (re)creating life and possibility just by existing. Our power of place, in body and land, can link and strengthen all Indigenous sovereignty movements when our communities take up the call to foster each person’s fluid potential.
Although this entire project is creative, as a PhD with creative practice component, this project is an ebb and flow of written and other media components. Most of the ‘creative component’ occurred during the co-research stage of this thesis and has been documented via photographs, video, participant testimony, soundscapes, and poetry on a separate, companion website (https://transjoy.cargo.site/). These artifacts of ritual research are also discussed within the harvest (data) section of the written portion, but reader/listeners are encouraged to view the website in tandem. Poetry, narrative, and soundscapes (hyperlinks or bone icons) weave throughout the written portion to create a multi-sensory experience that privileges my roots in aural tradition. Together, the performances, website, poetry, and soundscapes constitute roughly thirty percent of the final thesis, weighing more heavily on a written portion of seventy percent. Listener/readers are encouraged to experience the written and multi-media portions in tandem, cycling back and forth in a playful spirit as the next step of creative practice: listener participation. Please enter this project with the care and excitement invited of all listeners when the storyteller asks, “are you ready to hear a story?”

year: 2023