title: Exotic weeds and fluctuating microclimate can constrain native plant regeneration in urban forest restoration

authors: Wallace, Kiri Joy

subjects: Science & Technology

abstract: Restoring forest structure and composition is an important component of urban land management, but we lack clear understanding of the mechanisms driving restoration success. Here we studied two indicators of restoration success in temperate rainforests: native tree regeneration and epiphyte colonization. We hypothesized that ecosystem properties such as forest canopy openness, abundance of exotic herbaceous weeds, and the microclimate directly affect the density and diversity of native tree seedlings and epiphytes. Relationships between environmental conditions and the plant community were investigated in 27 restored urban forests spanning 3–70 years in age and in unrestored and remnant urban forests. We used structural equation modelling to determine the direct and indirect drivers of native tree regeneration and epiphyte colonization in the restored forests. Compared to remnant forest, unrestored forest had fewer native canopy tree species, significantly more light reaching the forest floor annually, and higher exotic weed cover. Additionally, epiphyte density was lower and native tree regeneration density was marginally lower in the unrestored forests. In restored forests, light availability was reduced to levels found in remnant forests within 20 years of restoration planting, followed shortly thereafter by declines in herbaceous exotic weeds and reduced fluctuation of relative humidity and soil temperatures. Contrary to expectations, canopy openness was only an indirect driver of tree regeneration and epiphyte colonization, but it directly regulated weed cover and microclimatic fluctuations, both of which directly drove the density and richness of regeneration and epiphyte colonization. Epiphyte density and diversity were also positively related to forest basal area, as large trees provide physical habitat for colonization. These results imply that ecosystem properties change predictably after initial restoration plantings, and that reaching critical thresholds in some ecosystem properties makes conditions suitable for the regeneration of late successional species, which is vital for restoration success and long-term ecosystem sustainability. Abiotic and biotic conditions that promote tree regeneration and epiphyte colonization will likely be present in forests with a basal area ≥27 m²/ha. We recommend that urban forest restoration plantings be designed to promote rapid canopy closure to reduce light availability, suppress herbaceous weeds, and stabilize the microclimate.

text: Exotic weeds and fluctuating microclimate can constrain native plant regeneration in urban forest restoration Restoring forest structure and composition is an important component of urban land management, but we lack clear understanding of the mechanisms driving restoration success. Here we studied two indicators of restoration success in temperate rainforests: native tree regeneration and epiphyte colonization. We hypothesized that ecosystem properties such as forest canopy openness, abundance of exotic herbaceous weeds, and the microclimate directly affect the density and diversity of native tree seedlings and epiphytes. Relationships between environmental conditions and the plant community were investigated in 27 restored urban forests spanning 3–70 years in age and in unrestored and remnant urban forests. We used structural equation modelling to determine the direct and indirect drivers of native tree regeneration and epiphyte colonization in the restored forests. Compared to remnant forest, unrestored forest had fewer native canopy tree species, significantly more light reaching the forest floor annually, and higher exotic weed cover. Additionally, epiphyte density was lower and native tree regeneration density was marginally lower in the unrestored forests. In restored forests, light availability was reduced to levels found in remnant forests within 20 years of restoration planting, followed shortly thereafter by declines in herbaceous exotic weeds and reduced fluctuation of relative humidity and soil temperatures. Contrary to expectations, canopy openness was only an indirect driver of tree regeneration and epiphyte colonization, but it directly regulated weed cover and microclimatic fluctuations, both of which directly drove the density and richness of regeneration and epiphyte colonization. Epiphyte density and diversity were also positively related to forest basal area, as large trees provide physical habitat for colonization. These results imply that ecosystem properties change predictably after initial restoration plantings, and that reaching critical thresholds in some ecosystem properties makes conditions suitable for the regeneration of late successional species, which is vital for restoration success and long-term ecosystem sustainability. Abiotic and biotic conditions that promote tree regeneration and epiphyte colonization will likely be present in forests with a basal area ≥27 m²/ha. We recommend that urban forest restoration plantings be designed to promote rapid canopy closure to reduce light availability, suppress herbaceous weeds, and stabilize the microclimate.

year: 2017

title: Miocene tubular concretions in East Coast Basin, New Zealand: Analogue for the subsurface plumbing of cold seeps

authors: Nyman, Stephanie Leigh

subjects: cold seep

abstract: The uplifted accretionary prism of East Coast Basin, in Hikurangi Margin, North Island, New Zealand, exposes late Miocene slope mudrocks (Whangaehu Mudstone, < 10% carbonate) in coastal cliffs north of Cape Turnagain that contain conspicuous tubular carbonate concretions (50–85% carbonate) supporting near-central conduits. Pipe and bulbous morphologies dominate, ranging in exposed length up to 5 m and up to 1 m in diameter. The concretions were formed by the precipitation of micritic dolomite (and calcite) cement within the host mudstone at shallow burial depths (< 100 m). δ13C values of the cement range from − 22 to + 13‰ PDB and are interpreted to reflect carbonate precipitation from either the extensive anaerobic oxidation of methane (AOM) and/or mixing of microbial methane and methanogenic CO2. AOM is confirmed by lipid biomarker evidence indicating that methane oxidation occurred in the sediments at the time of carbonate precipitation. The mixed dolomite/calcite mineralogies and the trend of δ13C in the tubular concretions from strongly negative to strongly positive values are interpreted to reflect methane oxidation from the onset of ascent through to the end of a migration event. Depleted and enriched δ18O values suggest an evolved fluid source influenced by the dissociation of gas hydrates. Collectively, our results indicate that the tubular concretions within the upper slope mudstones delineate parts of the subsurface plumbing network of a cold seep system on the late Miocene paleo-Hikurangi Margin in which the fluids were sourced from ascending methane. The intermediate location of the Whangaehu concretions between older (early Miocene) seep carbonates to the west and modern ones offshore to the east indicates a progressive eastwards shift with time of a long-lived, if only periodically active, seep system. The concretionary plumbing features at Whangaehu provide a conceptual model for subsurface fluid pathways and seep-related processes beneath the modern Hikurangi Margin seabed, and possibly also for other modern and ancient cold seep carbonate systems.

text: Miocene tubular concretions in East Coast Basin, New Zealand: Analogue for the subsurface plumbing of cold seeps The uplifted accretionary prism of East Coast Basin, in Hikurangi Margin, North Island, New Zealand, exposes late Miocene slope mudrocks (Whangaehu Mudstone, < 10% carbonate) in coastal cliffs north of Cape Turnagain that contain conspicuous tubular carbonate concretions (50–85% carbonate) supporting near-central conduits. Pipe and bulbous morphologies dominate, ranging in exposed length up to 5 m and up to 1 m in diameter. The concretions were formed by the precipitation of micritic dolomite (and calcite) cement within the host mudstone at shallow burial depths (< 100 m). δ13C values of the cement range from − 22 to + 13‰ PDB and are interpreted to reflect carbonate precipitation from either the extensive anaerobic oxidation of methane (AOM) and/or mixing of microbial methane and methanogenic CO2. AOM is confirmed by lipid biomarker evidence indicating that methane oxidation occurred in the sediments at the time of carbonate precipitation. The mixed dolomite/calcite mineralogies and the trend of δ13C in the tubular concretions from strongly negative to strongly positive values are interpreted to reflect methane oxidation from the onset of ascent through to the end of a migration event. Depleted and enriched δ18O values suggest an evolved fluid source influenced by the dissociation of gas hydrates. Collectively, our results indicate that the tubular concretions within the upper slope mudstones delineate parts of the subsurface plumbing network of a cold seep system on the late Miocene paleo-Hikurangi Margin in which the fluids were sourced from ascending methane. The intermediate location of the Whangaehu concretions between older (early Miocene) seep carbonates to the west and modern ones offshore to the east indicates a progressive eastwards shift with time of a long-lived, if only periodically active, seep system. The concretionary plumbing features at Whangaehu provide a conceptual model for subsurface fluid pathways and seep-related processes beneath the modern Hikurangi Margin seabed, and possibly also for other modern and ancient cold seep carbonate systems.

year: 2010

title: Māori engagement with early childhood education in a low-socioeconomic area

authors: Nuri, Sinead

subjects: early childhood education

abstract: The early childhood education (ECE) options available to parents in New Zealand are many and varied. As a country New Zealand values ECE and has a high rate of engagement. However, despite a number of government initiatives targeting Māori and those from lower socio-economic areas Māori engagement remains low. This is widely acknowledged and the challenge is to not only find the reasons why but to also be responsive to the causes for low engagement.

Early learning services in New Zealand follow a curriculum that considers an holistic approach with the child at the centre of the learning. That curriculum is Te Whāriki: He whāriki mātauranga mō ngā mokopuna o Aotearoa. The curriculum recognises the potential of children and the importance of belonging in developing the whole child. 

ECE in New Zealand is important for children who are aged zero to five. It is during these early years that children will begin to develop an understanding of the world around them. The environment that children live in is important to their development and it is generally considered that those from low socio-economic areas are less likely to succeed than those from higher socio-economic areas.

This thesis investigated Māori engagement in ECE from one low socio-economic area in New Zealand using an overarching Kaupapa Māori methodology. Semi-structured interviews were held with five participants from the low socio-economic area using a case study research design. My analysis found that there were many reasons behind the parents' decisions to send their children to ECE or not. It can be concluded that Māori engagement with ECE is dependent upon parents’ early life experiences and their cultural values.

text: Māori engagement with early childhood education in a low-socioeconomic area The early childhood education (ECE) options available to parents in New Zealand are many and varied. As a country New Zealand values ECE and has a high rate of engagement. However, despite a number of government initiatives targeting Māori and those from lower socio-economic areas Māori engagement remains low. This is widely acknowledged and the challenge is to not only find the reasons why but to also be responsive to the causes for low engagement.

Early learning services in New Zealand follow a curriculum that considers an holistic approach with the child at the centre of the learning. That curriculum is Te Whāriki: He whāriki mātauranga mō ngā mokopuna o Aotearoa. The curriculum recognises the potential of children and the importance of belonging in developing the whole child. 

ECE in New Zealand is important for children who are aged zero to five. It is during these early years that children will begin to develop an understanding of the world around them. The environment that children live in is important to their development and it is generally considered that those from low socio-economic areas are less likely to succeed than those from higher socio-economic areas.

This thesis investigated Māori engagement in ECE from one low socio-economic area in New Zealand using an overarching Kaupapa Māori methodology. Semi-structured interviews were held with five participants from the low socio-economic area using a case study research design. My analysis found that there were many reasons behind the parents' decisions to send their children to ECE or not. It can be concluded that Māori engagement with ECE is dependent upon parents’ early life experiences and their cultural values.

year: 2024