title: Ecohydrological characterisation of Otakairangi wetland, Northland

authors: Douglas, Callum

subjects: wetland

abstract: Otakairangi wetland is a 2.6 km² remnant wetland located on the western edge of the Wairua River floodplain, around 15 km north-west from Whangarei. Otakairangi has experienced over 100 years of degradation with long term hydrological modifications aimed at enabling agricultural land use. This includes a large central drain that has effectively divided the wetland into two sections, removed the natural diffuse flows of the Otakairangi stream and lowered water tables. This central drain, coupled with border drainage and frequent fire events caused the peat within the wetland to become severely degraded and decreased biodiversity.
The ecohydrology of representative areas of the wetland was studied to assess the relationship between the anthropogenic disturbances and the wetland ecology and water level regime. The primary goal of this research was to characterise the wetland condition, which would aid in the development of future management goals and planning through measurement of wetland degradation and natural recovery.
The study focused on five key areas of the wetland, with several transect lines established to determine the extent of degradation and recovery. This includes two transects across the central drain and three extending from the wetland margins. Peat physical and chemical characteristics were measured in the field and laboratory, and then classified through statistical ordination techniques. Vegetation compositions and patterns were assessed along with foliage chemistry, and then compared to peat characteristics. Hydrological data were retrieved and analysed from eight automatic water level sites along a transect perpendicular to the central drain, while meteorological data was collected at a nearby Northland Regional Council rain gauge. Peat surface oscillation in the restiad bog and water chemistry were also examined.
Nutrients, isotopes (δ¹⁵N), heavy metals, and physical soil characteristics (such as bulk density and water pH) were highest in close proximity to the upper central drain and the northern border drain. A gradient was observed from the entrance of the central drain into the central north-eastern section of the wetland, with high fertility substrate and swamp conditions transitioning to low fertility bog-like conditions. This was also shown by the vegetation composition, with larger swamp species such as flax (Phormium tenax) transitioning to sedges (Machaerina teretifolia) and ferns (Gleichenia dicarpa) and then to the restiad bog species Empodisma robustum. Low nutrient conditions were present elsewhere in the wetland, such as the southern section by the southern border drain and southern central drain. Both exhibited low fertility, the area around the southern central drain was dominated by large patches of M. teretifolia and small patches of E. robustum (fen-bog transitional), while the area by the southern drain was predominantly G. dicarpa and Leptospermum scoparium (fen). A natural spread of E. robustum is restoring the wetland, in terms of natural vegetation composition and peat substrate functionality, as indicated by analysis of peat cores from beneath sites in which it dominated.
The water levels in central areas of the wetland (100 - 290 m from the central drain) were relatively stable, with fluctuations around large rainfall events. These areas had rainfall as the primary water input, as they were independent from any surficial flows originating from either the central drainage channel or border drainage. However, several flood events impacted the marginal wetland water tables (February 2018, May-July 2018) with the drainage channel flooding and inundating between 50-100 m of the wetland area north-east of the central drain. In contrast, water table drawdown extended less than 20 m from the central drain, with the 20 m site experiencing mean water tables 1.5 m above that of the mean central drain water level.
The major risk to the wetland is continued flood inundation from the nutrient and sediment-rich waters from the surrounding catchment. Recommendations for management include improving the water quality from the headwaters to the wetland entrance through onsite farm management, engineering structures such as constructed wetlands or buffer zones to reduce flood inundation of the wetland. Internal restoration includes spreading the main peat forming species, Empodisma robustum, to areas in which it is currently absent, and a feasibility study for the re-introduction of the locally extinct Sporadanthus ferrugineus to the bog area.

text: Ecohydrological characterisation of Otakairangi wetland, Northland Otakairangi wetland is a 2.6 km² remnant wetland located on the western edge of the Wairua River floodplain, around 15 km north-west from Whangarei. Otakairangi has experienced over 100 years of degradation with long term hydrological modifications aimed at enabling agricultural land use. This includes a large central drain that has effectively divided the wetland into two sections, removed the natural diffuse flows of the Otakairangi stream and lowered water tables. This central drain, coupled with border drainage and frequent fire events caused the peat within the wetland to become severely degraded and decreased biodiversity.
The ecohydrology of representative areas of the wetland was studied to assess the relationship between the anthropogenic disturbances and the wetland ecology and water level regime. The primary goal of this research was to characterise the wetland condition, which would aid in the development of future management goals and planning through measurement of wetland degradation and natural recovery.
The study focused on five key areas of the wetland, with several transect lines established to determine the extent of degradation and recovery. This includes two transects across the central drain and three extending from the wetland margins. Peat physical and chemical characteristics were measured in the field and laboratory, and then classified through statistical ordination techniques. Vegetation compositions and patterns were assessed along with foliage chemistry, and then compared to peat characteristics. Hydrological data were retrieved and analysed from eight automatic water level sites along a transect perpendicular to the central drain, while meteorological data was collected at a nearby Northland Regional Council rain gauge. Peat surface oscillation in the restiad bog and water chemistry were also examined.
Nutrients, isotopes (δ¹⁵N), heavy metals, and physical soil characteristics (such as bulk density and water pH) were highest in close proximity to the upper central drain and the northern border drain. A gradient was observed from the entrance of the central drain into the central north-eastern section of the wetland, with high fertility substrate and swamp conditions transitioning to low fertility bog-like conditions. This was also shown by the vegetation composition, with larger swamp species such as flax (Phormium tenax) transitioning to sedges (Machaerina teretifolia) and ferns (Gleichenia dicarpa) and then to the restiad bog species Empodisma robustum. Low nutrient conditions were present elsewhere in the wetland, such as the southern section by the southern border drain and southern central drain. Both exhibited low fertility, the area around the southern central drain was dominated by large patches of M. teretifolia and small patches of E. robustum (fen-bog transitional), while the area by the southern drain was predominantly G. dicarpa and Leptospermum scoparium (fen). A natural spread of E. robustum is restoring the wetland, in terms of natural vegetation composition and peat substrate functionality, as indicated by analysis of peat cores from beneath sites in which it dominated.
The water levels in central areas of the wetland (100 - 290 m from the central drain) were relatively stable, with fluctuations around large rainfall events. These areas had rainfall as the primary water input, as they were independent from any surficial flows originating from either the central drainage channel or border drainage. However, several flood events impacted the marginal wetland water tables (February 2018, May-July 2018) with the drainage channel flooding and inundating between 50-100 m of the wetland area north-east of the central drain. In contrast, water table drawdown extended less than 20 m from the central drain, with the 20 m site experiencing mean water tables 1.5 m above that of the mean central drain water level.
The major risk to the wetland is continued flood inundation from the nutrient and sediment-rich waters from the surrounding catchment. Recommendations for management include improving the water quality from the headwaters to the wetland entrance through onsite farm management, engineering structures such as constructed wetlands or buffer zones to reduce flood inundation of the wetland. Internal restoration includes spreading the main peat forming species, Empodisma robustum, to areas in which it is currently absent, and a feasibility study for the re-introduction of the locally extinct Sporadanthus ferrugineus to the bog area.

year: 2019

title: The Stock Market, the Housing Market and Consumption

authors: Shen, Xin

subjects: Wealth effects

abstract: There is a long history of examining the relationship between consumption and wealth. The recent subprime mortgage crisis in the US and the European sovereign debt crisis associated with the remarkable fluctuations in both stock and housing markets have brought new concerns over the response of consumer spending to asset price shocks. This thesis re-investigates the relationship between consumption, income, financial and housing wealth: specifically, the wealth effect on consumption based on both time-series data in an examination of the US and panel data in an examination of OECD countries. It is argued that nonlinear estimation might provide a better explanation of fluctuations in the relationship between consumption and wealth, given the nature of the studied variables and the complexity of economic systems. The econometric methods employed include the Markov regime-switching approach, the quantile autoregressive distributed-lag framework, panel unit root and cointegration tests, and a panel vector autoregressive procedure. In terms of the US market, only weak evidence of a linear cointegrating relationship is found between consumption, income and wealth. It suggests that the consumption-wealth relation is better characterised in regime-specific terms. Furthermore, the transition probabilities between regimes are time-varying and driven by monetary indicators such as interest rates. In addition, different speeds of adjustment across the range of quantiles are identified in the long-run relationship between consumption, income and wealth. Wealth effects are found to be larger in lower quantiles. The findings imply that asymmetric monetary policies should be responsible for the movement in asset prices in analysing future inflation and aggregate demand due to the sensitivity of financial and housing wealth effects in different economic states.
In OECD studies, cointegration evidence is only observed in market-based countries, not in bank-based economies. Moreover, the wealth effects are found to be larger in market-based than in bank-based countries. In addition, since a positive wealth effect caused by an increase in capital value of housing might be partly offset by a negative price effect caused by an increase in the cost of housing services, the ‘net housing wealth effect’ actually is found to be slightly smaller than the stock market wealth effect in OECD countries. However, due to the significant boom in real estate markets since the 1990s, the housing wealth effect has clearly exceeded the share market wealth effect over the past decade. The results show that asset wealth has asymmetric effects on consumption, with stronger and more persistent effects from positive asset wealth shocks.

text: The Stock Market, the Housing Market and Consumption There is a long history of examining the relationship between consumption and wealth. The recent subprime mortgage crisis in the US and the European sovereign debt crisis associated with the remarkable fluctuations in both stock and housing markets have brought new concerns over the response of consumer spending to asset price shocks. This thesis re-investigates the relationship between consumption, income, financial and housing wealth: specifically, the wealth effect on consumption based on both time-series data in an examination of the US and panel data in an examination of OECD countries. It is argued that nonlinear estimation might provide a better explanation of fluctuations in the relationship between consumption and wealth, given the nature of the studied variables and the complexity of economic systems. The econometric methods employed include the Markov regime-switching approach, the quantile autoregressive distributed-lag framework, panel unit root and cointegration tests, and a panel vector autoregressive procedure. In terms of the US market, only weak evidence of a linear cointegrating relationship is found between consumption, income and wealth. It suggests that the consumption-wealth relation is better characterised in regime-specific terms. Furthermore, the transition probabilities between regimes are time-varying and driven by monetary indicators such as interest rates. In addition, different speeds of adjustment across the range of quantiles are identified in the long-run relationship between consumption, income and wealth. Wealth effects are found to be larger in lower quantiles. The findings imply that asymmetric monetary policies should be responsible for the movement in asset prices in analysing future inflation and aggregate demand due to the sensitivity of financial and housing wealth effects in different economic states.
In OECD studies, cointegration evidence is only observed in market-based countries, not in bank-based economies. Moreover, the wealth effects are found to be larger in market-based than in bank-based countries. In addition, since a positive wealth effect caused by an increase in capital value of housing might be partly offset by a negative price effect caused by an increase in the cost of housing services, the ‘net housing wealth effect’ actually is found to be slightly smaller than the stock market wealth effect in OECD countries. However, due to the significant boom in real estate markets since the 1990s, the housing wealth effect has clearly exceeded the share market wealth effect over the past decade. The results show that asset wealth has asymmetric effects on consumption, with stronger and more persistent effects from positive asset wealth shocks.

year: 2014

title: Māori experiences of bipolar disorder: pathways to recovery

authors: Waitoki, Waikaremoana

abstract: The findings of this research highlighted pathways into mental illness for Maori that could have been avoided earlier. The pathways to recovery however, showed the critical importance of maintaining connections with significant family members over the lifespan. Exposure to varying levels of childhood adversity, such as sexual and physical violence, parental mental illness, multiple and/or abusive foster care, and abandonment issues led to acute levels of post-traumatic stress, substance abuse, poor relationship choices, depression, anxiety and safety issues.

text: Māori experiences of bipolar disorder: pathways to recovery The findings of this research highlighted pathways into mental illness for Maori that could have been avoided earlier. The pathways to recovery however, showed the critical importance of maintaining connections with significant family members over the lifespan. Exposure to varying levels of childhood adversity, such as sexual and physical violence, parental mental illness, multiple and/or abusive foster care, and abandonment issues led to acute levels of post-traumatic stress, substance abuse, poor relationship choices, depression, anxiety and safety issues.

year: 2014