title: The reassembly of soil food web structure and functioning in restored urban forests across Aotearoa - New Zealand

authors: Rai, Bibishan

abstract: Soil food webs play a central role in the successful restoration of critical ecosystem processes. Yet, we lack an understanding of how these highly diverse and functionally complex belowground communities reassemble in forests undergoing restoration, and the factors responsible for varying trajectories of soil community reassembly. Even more poorly understood is the reassembly of soil invertebrates across multiple trophic levels after disturbance. Moreover, any potential effect of ecological succession on food web structural properties (connectance and maximum trophic level) and its implications on soil invertebrate trophic functions remains poorly understood. In this PhD thesis, I investigate the effect of restoration age and biotic and abiotic characteristics of restored forests on the reassembly of soil invertebrate communities across different trophic groups. I also explore the effect of the aforementioned predictors on soil food web structure and associated ecosystem functioning.
I sampled soil invertebrate communities from 70 urban restored forests, as well as three unrestored and three remnant urban forests. All forest sites were distributed across eight cities in Aotearoa, New Zealand and were historically occupied by native vegetation until cleared for either agriculture or urban development. The sites were then planted with native woody species between six and 60 years prior to this research, forming a chronosequence of forest succession. In addition to soil invertebrates, vegetation data (e.g., mean tree diameter, tree species richness) and site characteristics (e.g., litter depth, soil temperature) were also collected from these forests. I identified the soil invertebrates into major size-based functional groups (i.e., microfauna, mesofauna and macrofauna) and further into trophic levels: detritivores, fungivores, herbivores, omnivores and predators. Additionally, I quantified the abundance, biomass and mean body mass of all soil invertebrates. Finally, I constructed 70 local food webs across the restored forest sites and quantified the flux of energy between different feeding groups and their food sources to estimate five important ecosystem functions in soil food webs: detritivory, bacterivory, fungivory, herbivory and predation.
I analysed the relative importance of restored forest age and environmental variables as predictors of variation in soil invertebrate communities. I found that restoration age, in itself, had no discernible effect on the abundance, biomass or mean body size of soil invertebrate communities. Instead, site characteristics like mean tree diameter, tree species richness, litter depth and soil temperature were the main drivers of variability in soil communities. Notably, these factors influenced larger macrofauna and mesofauna more than nematodes. However, when I modelled the effects of restoration age on soil communities in a structural equation modelling framework, taking into account bottom-up effects from plant communities to invertebrate predators, restoration age was shown to have indirect effects on the biomass of mesofauna decomposers, omnivores and nematode predators. Finally, by investigating shifts in food web structure and resulting changes in energy fluxes across trophic levels, I found that forest restoration age did not directly influence either the structure (connectance, maximum trophic level) or the five examined trophic functions of the soil food webs. Instead, effects of forest restoration age occurred through changes in vegetation characteristics as forest succession progresses.
My results suggests that forest age is not a direct major driver of the reassembly of soil invertebrate communities. Instead, mean tree diameter, tree species richness, litter depth, and soil temperature play important roles in the process. My results show the significance of planting trees that can grow large, promoting species diversity and allowing leaf litter to accumulate naturally to support soil invertebrate community of different trophic functions. Through my results, I also show how the aforementioned vegetation characteristics can contribute to flow of energy in the soil food web. In addition to demonstrating how crucial food web structural properties are to energy flow via trophic interactions such as detritivory, fungivory and predation, this research also highlights the interconnectedness of above and belowground ecosystems. Taken together, my findings suggest that urban restoration efforts should focus on promoting these beneficial vegetation characteristics, alongside considering food web complexity, to optimize trophic functions performed by soil food webs.

text: The reassembly of soil food web structure and functioning in restored urban forests across Aotearoa - New Zealand Soil food webs play a central role in the successful restoration of critical ecosystem processes. Yet, we lack an understanding of how these highly diverse and functionally complex belowground communities reassemble in forests undergoing restoration, and the factors responsible for varying trajectories of soil community reassembly. Even more poorly understood is the reassembly of soil invertebrates across multiple trophic levels after disturbance. Moreover, any potential effect of ecological succession on food web structural properties (connectance and maximum trophic level) and its implications on soil invertebrate trophic functions remains poorly understood. In this PhD thesis, I investigate the effect of restoration age and biotic and abiotic characteristics of restored forests on the reassembly of soil invertebrate communities across different trophic groups. I also explore the effect of the aforementioned predictors on soil food web structure and associated ecosystem functioning.
I sampled soil invertebrate communities from 70 urban restored forests, as well as three unrestored and three remnant urban forests. All forest sites were distributed across eight cities in Aotearoa, New Zealand and were historically occupied by native vegetation until cleared for either agriculture or urban development. The sites were then planted with native woody species between six and 60 years prior to this research, forming a chronosequence of forest succession. In addition to soil invertebrates, vegetation data (e.g., mean tree diameter, tree species richness) and site characteristics (e.g., litter depth, soil temperature) were also collected from these forests. I identified the soil invertebrates into major size-based functional groups (i.e., microfauna, mesofauna and macrofauna) and further into trophic levels: detritivores, fungivores, herbivores, omnivores and predators. Additionally, I quantified the abundance, biomass and mean body mass of all soil invertebrates. Finally, I constructed 70 local food webs across the restored forest sites and quantified the flux of energy between different feeding groups and their food sources to estimate five important ecosystem functions in soil food webs: detritivory, bacterivory, fungivory, herbivory and predation.
I analysed the relative importance of restored forest age and environmental variables as predictors of variation in soil invertebrate communities. I found that restoration age, in itself, had no discernible effect on the abundance, biomass or mean body size of soil invertebrate communities. Instead, site characteristics like mean tree diameter, tree species richness, litter depth and soil temperature were the main drivers of variability in soil communities. Notably, these factors influenced larger macrofauna and mesofauna more than nematodes. However, when I modelled the effects of restoration age on soil communities in a structural equation modelling framework, taking into account bottom-up effects from plant communities to invertebrate predators, restoration age was shown to have indirect effects on the biomass of mesofauna decomposers, omnivores and nematode predators. Finally, by investigating shifts in food web structure and resulting changes in energy fluxes across trophic levels, I found that forest restoration age did not directly influence either the structure (connectance, maximum trophic level) or the five examined trophic functions of the soil food webs. Instead, effects of forest restoration age occurred through changes in vegetation characteristics as forest succession progresses.
My results suggests that forest age is not a direct major driver of the reassembly of soil invertebrate communities. Instead, mean tree diameter, tree species richness, litter depth, and soil temperature play important roles in the process. My results show the significance of planting trees that can grow large, promoting species diversity and allowing leaf litter to accumulate naturally to support soil invertebrate community of different trophic functions. Through my results, I also show how the aforementioned vegetation characteristics can contribute to flow of energy in the soil food web. In addition to demonstrating how crucial food web structural properties are to energy flow via trophic interactions such as detritivory, fungivory and predation, this research also highlights the interconnectedness of above and belowground ecosystems. Taken together, my findings suggest that urban restoration efforts should focus on promoting these beneficial vegetation characteristics, alongside considering food web complexity, to optimize trophic functions performed by soil food webs.

year: 2024-09-02

title: Chemical aspects of saponin bioactivity and ovine photosensitization diseases

authors: Loader, Jared I.

abstract: A general review of saponin chemistry, bioactivities and of chemical aspects of saponin-associated hepatogenous photosensitization of ruminants (sheep, goats, and cattle) is presented. 
A field trial was undertaken to explore the genin dose/response hypothesis that saponins produced by the plant Narthecium ossifragum may be the direct cause of the toxicity leading to the photosensitization disease alveld seen in Norwegian lambs grazing N. ossifragum containing pastures. The genin content of N. ossifragum leaves from 2 control and 2 outbreak pasture areas, in a region of Norway known for periodic livestock outbreaks of alveld, ranged from 4553 to 10879 mg/kg DM. No significant statistical differences in the mean sapogenin content from the 2 control and 2 outbreak pasture areas were found. Total faecal sapogenin levels determined for lambs grazing the 2 control and 2 outbreak areas ranged from 973 to 36314 mg/kg DM. No obvious relationships between faecal sapogenin levels of lambs exhibiting external alveld symptoms and lambs not exhibiting symptoms were identified. The data does not support the hypothesis that saponins are the sole causative agent for the development of alveld disease symptoms in lambs grazing pastures containing N. ossifragum. 
Genin levels in Scottish collections of N. ossifragum plant material, gathered from pasture on which sheep were photosensitized, were determined. Elevated levels of sarsasapogenin and smilagenin containing saponins were found in flower heads (ca. 18000 mg/kg DM). Significant levels of free genins were found in plant roots (832-1184 mg/kg DM). The percentage contribution (ca. 45-65%) of smilagenin (a 25R-genin) in the Scottish samples was typically 2-4 times greater than is the case for Norwegian collections of N. ossifragum (typically ca. 10-15%). 
A field trial involving the daily intraruminal administration of a 1:4 mixture of [2,2,4,4-2H4]sarsasapogenin and [2,2,4,4-2H4]episarsasapogenin to 4 ewes, their twin lambs, and to 3 weaned lambs over a 21 day period was undertaken in Norway. The results showed that the isotope-dilution methodology can be applied under field conditions to estimate the uptake of sapogenins from plant material under conditions characteristically associated with the development of al veld. 
Mother ewes, on average, consumed 2-3 times the daily weight of N. ossifragum (ca. 700-750 g DM/day) consumed by the lambs (ca. 200-250 g DM/day). Percentage deuterium ratios, determined using SIM GC-MS protocols, while lower that anticipated, were consistent across the animals involved in the trial (between ca. 2-3%). Average N. ossifragum intakes, calculated relative to live-weights, were determined for all sheep involved in the trial. No correlation between the quantity of N. ossifragum consumed and live-weight (g DM day/kg) and the development of alveld was identified. 
The synthesis of sarsasapogenin β-D-galactoside, episarsasapogenin β-D-glucoside, episarsasapogenin β-D-galactoside, betulin 3-(β-D-glucoside) and betulin 3,28-(β-D-diglucoside), was performed via Koenig-Knorr coupling of sarsasapogenin, episarsasapogenin, or betulin with 2,3,4,6-tetra-0-acetyl-α-D-glucopyranosyl bromide, or the corresponding galactoside, followed by hydrolysis of the resulting tetra-0-acetyl-β-Dglycosides.Structures of intermediates, and product glycosides were established using a combination of ES-MS and one- and two-dimensional NMR spectral data. 
The synthesized sarsasapogenin, episarsasapogenin and betulin saponins, 4-methoxyfuran-2(5H)-one 5-(β-D-glucoside), Yucca schidigera 70° Brix extract, a methanol conjugate extract of N. ossifragum leaves and the active triketone fraction (triketone oil) from East Cape Manuka oil were subjected to a bioactivity evaluation against a range of bacterial and fungal organisms using the agar gel well diffusion technique. A possible structure-activity relationship amongst the synthesized saponins is discussed. 
The activity of triketone oil against two fish-pathogenic strains of Saprolegnia parasiticawas evaluated. The evaluation, performed in vitro, required the use of small percentages of water-miscible organic solvents and phosphate buffer solutions to obtain homogenous aqueous solutions. Inhibition of S. parasitica growth was seen at triketone oil concentrations of: (i) 150 and 200 ppm using aqueous solutions containing 0.5% and 1.0% pyrrolidinone, each containing 0.5% Tween 80 and (ii) at 150 and 200 ppm, at both pH 7 .0 and 7.5 of a 0.25 molL-1  phosphate buffer solution. An in vivo toxicity trial found that East Cape triketone oil at 200 ppm was acutely toxic to Atlantic salmon fry, with a 50% mortality rate after a 2 h single dose static bath exposure.

text: Chemical aspects of saponin bioactivity and ovine photosensitization diseases A general review of saponin chemistry, bioactivities and of chemical aspects of saponin-associated hepatogenous photosensitization of ruminants (sheep, goats, and cattle) is presented. 
A field trial was undertaken to explore the genin dose/response hypothesis that saponins produced by the plant Narthecium ossifragum may be the direct cause of the toxicity leading to the photosensitization disease alveld seen in Norwegian lambs grazing N. ossifragum containing pastures. The genin content of N. ossifragum leaves from 2 control and 2 outbreak pasture areas, in a region of Norway known for periodic livestock outbreaks of alveld, ranged from 4553 to 10879 mg/kg DM. No significant statistical differences in the mean sapogenin content from the 2 control and 2 outbreak pasture areas were found. Total faecal sapogenin levels determined for lambs grazing the 2 control and 2 outbreak areas ranged from 973 to 36314 mg/kg DM. No obvious relationships between faecal sapogenin levels of lambs exhibiting external alveld symptoms and lambs not exhibiting symptoms were identified. The data does not support the hypothesis that saponins are the sole causative agent for the development of alveld disease symptoms in lambs grazing pastures containing N. ossifragum. 
Genin levels in Scottish collections of N. ossifragum plant material, gathered from pasture on which sheep were photosensitized, were determined. Elevated levels of sarsasapogenin and smilagenin containing saponins were found in flower heads (ca. 18000 mg/kg DM). Significant levels of free genins were found in plant roots (832-1184 mg/kg DM). The percentage contribution (ca. 45-65%) of smilagenin (a 25R-genin) in the Scottish samples was typically 2-4 times greater than is the case for Norwegian collections of N. ossifragum (typically ca. 10-15%). 
A field trial involving the daily intraruminal administration of a 1:4 mixture of [2,2,4,4-2H4]sarsasapogenin and [2,2,4,4-2H4]episarsasapogenin to 4 ewes, their twin lambs, and to 3 weaned lambs over a 21 day period was undertaken in Norway. The results showed that the isotope-dilution methodology can be applied under field conditions to estimate the uptake of sapogenins from plant material under conditions characteristically associated with the development of al veld. 
Mother ewes, on average, consumed 2-3 times the daily weight of N. ossifragum (ca. 700-750 g DM/day) consumed by the lambs (ca. 200-250 g DM/day). Percentage deuterium ratios, determined using SIM GC-MS protocols, while lower that anticipated, were consistent across the animals involved in the trial (between ca. 2-3%). Average N. ossifragum intakes, calculated relative to live-weights, were determined for all sheep involved in the trial. No correlation between the quantity of N. ossifragum consumed and live-weight (g DM day/kg) and the development of alveld was identified. 
The synthesis of sarsasapogenin β-D-galactoside, episarsasapogenin β-D-glucoside, episarsasapogenin β-D-galactoside, betulin 3-(β-D-glucoside) and betulin 3,28-(β-D-diglucoside), was performed via Koenig-Knorr coupling of sarsasapogenin, episarsasapogenin, or betulin with 2,3,4,6-tetra-0-acetyl-α-D-glucopyranosyl bromide, or the corresponding galactoside, followed by hydrolysis of the resulting tetra-0-acetyl-β-Dglycosides.Structures of intermediates, and product glycosides were established using a combination of ES-MS and one- and two-dimensional NMR spectral data. 
The synthesized sarsasapogenin, episarsasapogenin and betulin saponins, 4-methoxyfuran-2(5H)-one 5-(β-D-glucoside), Yucca schidigera 70° Brix extract, a methanol conjugate extract of N. ossifragum leaves and the active triketone fraction (triketone oil) from East Cape Manuka oil were subjected to a bioactivity evaluation against a range of bacterial and fungal organisms using the agar gel well diffusion technique. A possible structure-activity relationship amongst the synthesized saponins is discussed. 
The activity of triketone oil against two fish-pathogenic strains of Saprolegnia parasiticawas evaluated. The evaluation, performed in vitro, required the use of small percentages of water-miscible organic solvents and phosphate buffer solutions to obtain homogenous aqueous solutions. Inhibition of S. parasitica growth was seen at triketone oil concentrations of: (i) 150 and 200 ppm using aqueous solutions containing 0.5% and 1.0% pyrrolidinone, each containing 0.5% Tween 80 and (ii) at 150 and 200 ppm, at both pH 7 .0 and 7.5 of a 0.25 molL-1  phosphate buffer solution. An in vivo toxicity trial found that East Cape triketone oil at 200 ppm was acutely toxic to Atlantic salmon fry, with a 50% mortality rate after a 2 h single dose static bath exposure.

year: 2004

title: Site-specific performance rituals in the Anthropocene

authors: Claus, Johanna

abstract: In this creative practice PhD, I investigated site-specific performance rituals in the Anthropocene. Driven by the urge to respond to the challenges of the current time, I examined how different seasonal rituals might be expressed in specific sites in Aotearoa, New Zealand. Furthermore, including participants from diverse cultural backgrounds, and carrying an awareness of the complexities of colonialism, I analysed insights from key ritual experts to enhance my understanding of ritual practices within the specific socio-cultural and environmental context of Aotearoa. Inspired by critical posthumanist philosophies, I viewed ritual practices through a lens that considered the interconnectedness of technology, culture, and nature, moving beyond essentialist and dualistic tendencies. Inspired by (Haraway, 2007) and Braidotti (2019), I embraced a perspective of ‘staying with the trouble’ and ‘radical hope’ as a strategy to inspire commitments to safeguarding life on Earth amid increasing societal divisions, and environmental disasters.
Working at the intersection of various disciplines, I crafted a qualitative research design that embraced multiple ways of knowing through creative practice research. I gathered insights from four ritual experts grounded in mātauranga Māori or neo-Paganism through in-depth interviews, to comprehend multifaceted and culturally sensitive approaches to ritual practices in Aotearoa. Moreover, the creative investigation of four seasonal performance rituals served as the primary mode of inquiry (Niedderer & Roworth-Stokes, 2007; Skains, 2018). The methods used for these rituals included contemporary performance practices, eco-somatic movement, improvisation, site-specific dance, audience participation, and others.
The rich knowledge gained throughout these investigations is conveyed through the documentation of four seasonal rituals, presented in video works alongside this thesis. The findings are articulated in two empirical chapters, one focusing on the findings and analysis of the expert interviews and the other on the findings and analysis of four performance rituals, revealing nuanced and complex insights into the creation of site-specific performance rituals in the Anthropocene. Navigating site-specific performance practices as an immigrant necessitated continuous critical self-reflection on biases and assumptions, leading to intricate explorations of embodiment, identity, culture, nature, and the more-than-human world within a posthuman context. Operating in the liminal space of this tension alongside performer participants, ritual experts, and audience members yielded the articulation of my findings: a ritual score capable of accommodating the complexities of the Anthropocene.

text: Site-specific performance rituals in the Anthropocene In this creative practice PhD, I investigated site-specific performance rituals in the Anthropocene. Driven by the urge to respond to the challenges of the current time, I examined how different seasonal rituals might be expressed in specific sites in Aotearoa, New Zealand. Furthermore, including participants from diverse cultural backgrounds, and carrying an awareness of the complexities of colonialism, I analysed insights from key ritual experts to enhance my understanding of ritual practices within the specific socio-cultural and environmental context of Aotearoa. Inspired by critical posthumanist philosophies, I viewed ritual practices through a lens that considered the interconnectedness of technology, culture, and nature, moving beyond essentialist and dualistic tendencies. Inspired by (Haraway, 2007) and Braidotti (2019), I embraced a perspective of ‘staying with the trouble’ and ‘radical hope’ as a strategy to inspire commitments to safeguarding life on Earth amid increasing societal divisions, and environmental disasters.
Working at the intersection of various disciplines, I crafted a qualitative research design that embraced multiple ways of knowing through creative practice research. I gathered insights from four ritual experts grounded in mātauranga Māori or neo-Paganism through in-depth interviews, to comprehend multifaceted and culturally sensitive approaches to ritual practices in Aotearoa. Moreover, the creative investigation of four seasonal performance rituals served as the primary mode of inquiry (Niedderer & Roworth-Stokes, 2007; Skains, 2018). The methods used for these rituals included contemporary performance practices, eco-somatic movement, improvisation, site-specific dance, audience participation, and others.
The rich knowledge gained throughout these investigations is conveyed through the documentation of four seasonal rituals, presented in video works alongside this thesis. The findings are articulated in two empirical chapters, one focusing on the findings and analysis of the expert interviews and the other on the findings and analysis of four performance rituals, revealing nuanced and complex insights into the creation of site-specific performance rituals in the Anthropocene. Navigating site-specific performance practices as an immigrant necessitated continuous critical self-reflection on biases and assumptions, leading to intricate explorations of embodiment, identity, culture, nature, and the more-than-human world within a posthuman context. Operating in the liminal space of this tension alongside performer participants, ritual experts, and audience members yielded the articulation of my findings: a ritual score capable of accommodating the complexities of the Anthropocene.

year: 2024-05-27