title: Soil chronosequences and bacterial communities of the Central Transantarctic Mountains, Antarctica

authors: Scarrow, Joshua William

subjects: Antarctica

abstract: The Beardmore Glacier region of the Central Transantarctic Mountains (CTAM), approximately 600 km south of the McMurdo Dry Valleys (MDV), has been studied to a much lesser extent than the accessible MDV and other regions of the continent. The CTAM were visited in the 2010/2011 austral summer, and two concurrent studies undertaken; these are presented in the form of manuscripts for publication in peer-reviewed journals, as a thesis by publication.
Soil chronosequences in three of the largest ice-free areas (Ong Valley, Mount Achernar, and the Dominion Range), at altitudes above 1600 m along the polar plateau margin, were examined. Transects perpendicular to the current ice edge reveal a gradual increase in soil depth (from 2 cm to > 80 cm to underlying ice), weathering, horizonation, salt content, and a decrease in pH; all of these factors are consistent with increased soil development since time of deglaciation. Such fine scale variation in soil properties, previously overlooked in the CTAM region, cannot be mapped by Soil Taxonomy subgroups, as commonly utilised in Antarctic soil mapping. Patterns of soil thickness, clast abundance and soil chemistry all indicate a bi-modal form of soil development. It is proposed that the soil profile deepens by addition of englacial debris to the subsoil via the sublimation of underlying ice, and the weathering of supraglacial clasts at the soil surface.
The molecular characterization of bacterial communities in CTAM soils is the southernmost culture-independent soil survey to date. Community fingerprinting (ARISA) and 16S rRNA gene pyrosequencing demonstrated significantly different bacterial communities between eight discrete CTAM locations (5 at low altitude near the Ross Ice Shelf coast, 3 near the polar plateau > 1600 m). Abiotic environmental variables, especially those related to long-term exposure of soils to the atmosphere, correlate well with inter-site community variation. Mount Howe, the southernmost soil on the planet (87° S), harbours an extremely low biomass bacterial community, of a fundamentally different composition to all other sites. It appears that observed DNA sequences at Mount Howe are the result of atmospherically deposited bacteria, the soil being unable to support edaphic life due to extreme local climatic conditions.￼
These two studies extend previous knowledge of soil development and distribution, and microbial ecology, to the southernmost extent possible. These observations may serve as important baseline data for monitoring of this fragile system in the face of future and ongoing environmental changes.

text: Soil chronosequences and bacterial communities of the Central Transantarctic Mountains, Antarctica The Beardmore Glacier region of the Central Transantarctic Mountains (CTAM), approximately 600 km south of the McMurdo Dry Valleys (MDV), has been studied to a much lesser extent than the accessible MDV and other regions of the continent. The CTAM were visited in the 2010/2011 austral summer, and two concurrent studies undertaken; these are presented in the form of manuscripts for publication in peer-reviewed journals, as a thesis by publication.
Soil chronosequences in three of the largest ice-free areas (Ong Valley, Mount Achernar, and the Dominion Range), at altitudes above 1600 m along the polar plateau margin, were examined. Transects perpendicular to the current ice edge reveal a gradual increase in soil depth (from 2 cm to > 80 cm to underlying ice), weathering, horizonation, salt content, and a decrease in pH; all of these factors are consistent with increased soil development since time of deglaciation. Such fine scale variation in soil properties, previously overlooked in the CTAM region, cannot be mapped by Soil Taxonomy subgroups, as commonly utilised in Antarctic soil mapping. Patterns of soil thickness, clast abundance and soil chemistry all indicate a bi-modal form of soil development. It is proposed that the soil profile deepens by addition of englacial debris to the subsoil via the sublimation of underlying ice, and the weathering of supraglacial clasts at the soil surface.
The molecular characterization of bacterial communities in CTAM soils is the southernmost culture-independent soil survey to date. Community fingerprinting (ARISA) and 16S rRNA gene pyrosequencing demonstrated significantly different bacterial communities between eight discrete CTAM locations (5 at low altitude near the Ross Ice Shelf coast, 3 near the polar plateau > 1600 m). Abiotic environmental variables, especially those related to long-term exposure of soils to the atmosphere, correlate well with inter-site community variation. Mount Howe, the southernmost soil on the planet (87° S), harbours an extremely low biomass bacterial community, of a fundamentally different composition to all other sites. It appears that observed DNA sequences at Mount Howe are the result of atmospherically deposited bacteria, the soil being unable to support edaphic life due to extreme local climatic conditions.￼
These two studies extend previous knowledge of soil development and distribution, and microbial ecology, to the southernmost extent possible. These observations may serve as important baseline data for monitoring of this fragile system in the face of future and ongoing environmental changes.

year: 2013

title: The effects of urban forest restoration and environmental heterogeneity on microbial diversity and ecosystem functioning

authors: Mitchell, Grace

subjects: Restoration

abstract: Increasing global urbanisation poses extensive environmental threats, including the loss of biodiversity and associated ecosystem functions. Ecosystem restoration interventions like native plantings can assist in halting and reversing the degradation of forest patches in urban settings, which is particularly relevant for the United Nations’ decade of ecosystem restoration. While the benefits of restoration plantings for aboveground communities have been well established, belowground community responses remain understudied. It is assumed that the soil microbiome will self-assemble to a pre-disturbance state following restoration. However, as microorganisms are rarely the target of restoration interventions themselves, various questions remain regarding the extent to which microbial communities will respond and recover with aboveground plantings, and how environmental variability might influence trajectories of microbial community reassembly. In this thesis, I contribute to this knowledge gap by investigating the impacts of forest age since restoration alongside a suite of environmental covariates on microbial community responses. My fieldwork took place in a New Zealand-wide chronosequence of restored urban forest sites. I analysed the diversity and taxonomic composition of bacterial, archaeal, fungal, and protist communities from these soil samples using metabarcoding data in chapter 2. Furthermore, I investigated changes in total microbial biomass, bacterial and fungal taxonomic group biomass via PLFA, total basal respiration, the spatial variability of microbial biomass and respiration, and carbon metabolism on substrates of varying recalcitrance using MicroResp™ in chapter 3. My synthesised findings show that environmental variability is typically more explanatory of microbial responses than forest age alone. Plant community factors in particular—such as native woody seedling density and tree species richness—were most often linked with enhanced microbial diversity and respiration, as well as driving increased local spatial variability. Specific phylum-level shifts from metabarcoding data indicated microbiome recovery on a trajectory towards mature forest soil communities, yet PLFA data showed that community composition does not yet reflect fungal dominance as would be expected in a mature or fully recovered forest soil. This thesis provides a holistic assessment of microbial community responses to urban forest restoration interventions, by assessing both diversity and microbial functions at multiple taxonomic resolutions. In conclusion, results from my thesis highlight the importance of taking into account the recovery of the soil microbiome and its associated ecosystem functioning to improve both aboveground and belowground success in future forest restoration projects.

text: The effects of urban forest restoration and environmental heterogeneity on microbial diversity and ecosystem functioning Increasing global urbanisation poses extensive environmental threats, including the loss of biodiversity and associated ecosystem functions. Ecosystem restoration interventions like native plantings can assist in halting and reversing the degradation of forest patches in urban settings, which is particularly relevant for the United Nations’ decade of ecosystem restoration. While the benefits of restoration plantings for aboveground communities have been well established, belowground community responses remain understudied. It is assumed that the soil microbiome will self-assemble to a pre-disturbance state following restoration. However, as microorganisms are rarely the target of restoration interventions themselves, various questions remain regarding the extent to which microbial communities will respond and recover with aboveground plantings, and how environmental variability might influence trajectories of microbial community reassembly. In this thesis, I contribute to this knowledge gap by investigating the impacts of forest age since restoration alongside a suite of environmental covariates on microbial community responses. My fieldwork took place in a New Zealand-wide chronosequence of restored urban forest sites. I analysed the diversity and taxonomic composition of bacterial, archaeal, fungal, and protist communities from these soil samples using metabarcoding data in chapter 2. Furthermore, I investigated changes in total microbial biomass, bacterial and fungal taxonomic group biomass via PLFA, total basal respiration, the spatial variability of microbial biomass and respiration, and carbon metabolism on substrates of varying recalcitrance using MicroResp™ in chapter 3. My synthesised findings show that environmental variability is typically more explanatory of microbial responses than forest age alone. Plant community factors in particular—such as native woody seedling density and tree species richness—were most often linked with enhanced microbial diversity and respiration, as well as driving increased local spatial variability. Specific phylum-level shifts from metabarcoding data indicated microbiome recovery on a trajectory towards mature forest soil communities, yet PLFA data showed that community composition does not yet reflect fungal dominance as would be expected in a mature or fully recovered forest soil. This thesis provides a holistic assessment of microbial community responses to urban forest restoration interventions, by assessing both diversity and microbial functions at multiple taxonomic resolutions. In conclusion, results from my thesis highlight the importance of taking into account the recovery of the soil microbiome and its associated ecosystem functioning to improve both aboveground and belowground success in future forest restoration projects.

year: 2022

title: Mental health inpatient services: Improving our understanding of the needs of Maori when acutely unwell

authors: Wharewera-Mika, Julie

subjects: Maori

abstract: There are many possible explanations for the pattern of Maori overrepresentation in mental health acute services. This research project focuses on how services can optimally meet the needs of Maori to improve outcomes. This doctoral research in progress is about claiming space for Maori to have a voice in identifying factors that contribute to recovery and Whanau Ora, and offering recommendations to improve the effectiveness of existing services to better meet the needs of Maori Tangata Whaiora and Whanau.

text: Mental health inpatient services: Improving our understanding of the needs of Maori when acutely unwell There are many possible explanations for the pattern of Maori overrepresentation in mental health acute services. This research project focuses on how services can optimally meet the needs of Maori to improve outcomes. This doctoral research in progress is about claiming space for Maori to have a voice in identifying factors that contribute to recovery and Whanau Ora, and offering recommendations to improve the effectiveness of existing services to better meet the needs of Maori Tangata Whaiora and Whanau.

year: 2008