The Building Act 2004 now requires Territorial Authorities (TAs) to have in place a policy setting out how they intend making existing buildings that would be unable to withstand a moderate earthquake safe for their occupiers. Many of the resultant policies developed by TAs have put in place mandatory upgrade requirements that will force owners to expend large amounts of capital on seismic upgrading of their buildings. The challenge for the property owners and TAs alike is to make such development work economic or the result will be wide scale demolition of old buildings. This has serious implications for both heritage conservation and inner city revitalisation plans that are based on existing heritage buildings. This paper sets out the issues and challenges for the seismic upgrading of buildings in New Zealand and puts forward some potential solutions
The September and February earthquakes were terrifying and devastating. In February, 185 people were killed (this number excludes post earthquake related deaths) and several thousand injured. Damage to infrastructure above and below ground in and around Christchurch was widespread and it will take many years and billions of dollars to rebuild.
The ongoing effects of the big quakes and aftershocks are numerous, with the deepest impact being on those who lost family and friends, their livelihoods and homes.
What did Cantabrians do during the days, weeks and months of uncertainty and how have we responded? Many grieved, some left, some stayed, some arrived, many shovelled (liquefaction left thousands of tons of silt to be removed from homes and streets), and some used their expertise or knowledge to help in the recovery.
This book highlights just some of the projects staff and students from The Faculty of Environment, Society and Design have been involved in from September 2010 to October 2012. The work is ongoing and the plan is to publish another book to document progress and new projects.
The magnitude 7.8 earthquake that struck North Canterbury, on the east coast of New Zealand’s South Island on 14 November 2016 had significant impacts and implications for the community of Kaikōura and surrounding settlements. The magnitude and scope of this event has resulted in extensive and ongoing geological and geophysical research into the event. The current paper complements this research by providing a review of existing social science research and offering new analysis of the impact of the earthquake and its aftermath on community resilience in Kaikōura over the past five years. Results demonstrate the significant economic implications for tourism, and primary industries. Recovery has been slow, and largely dependent on restoring transportation networks, which helped catalyse cooperation among local hospitality providers. Challenges remain, however, and not all sectors or households have benefited equally from post-quake opportunities, and long-term recovery trajectories continue to be hampered by COVID-19 pandemic. The multiple ongoing and future stressors faced by Kaikōura require integrated and equitable approaches in order to build capability and capacity for locally based development pathways to ensure long-term community resilience.
An emerging water crisis is on the horizon and is poised to converge with several other impending problems in the 21st century. Future uncertainties such as climate change, peak oil and peak water are shifting the international focus from a business as usual approach to an emphasis on sustainable and resilient strategies that better meet these challenges. Cities are being reimagined in new ways that take a multidisciplinary approach, decompartmentalising functions and exploring ways in which urban systems can share resources and operate more like natural organisms. This study tested the landscape design implications of wastewater wetlands in the urban environment and evaluated their contribution to environmental sustainability, urban resilience and social development. Black and grey water streams were the central focus of this study and two types of wastewater wetlands, tidal flow (staged planning) and horizontal subsurface flow wetlands were tested through design investigations in the earthquake-affected city of Christchurch, New Zealand. These investigations found that the large area requirements of wastewater wetlands can be mitigated through landscape designs that enhance a matrix of open spaces and corridors in the city.
Wastewater wetlands when combined with other urban and rural services such as food production, energy generation and irrigation can aid in making communities more resilient. Landscape theory suggests that the design of wastewater wetlands must meet cultural thresholds of beauty and that the inclusion of waste and ecologies in creatively designed landscapes can deepen our emotional connection to nature and ourselves.
The city of Ōtautahi/Christchurch experienced a series of earthquakes that began on September 4th, 2010. The most damaging event occurred on February 22nd, 2011 but significant earthquakes also occurred on June 13th and December 23rd with aftershocks still occurring well into 2012. The resulting disaster is the second deadliest natural disaster in New Zealand’s history with 185 deaths. During 2011 the Canterbury earthquakes were one of the costliest disasters worldwide with an expected cost of up to $NZ30 billion.
Hundreds of commercial buildings and thousands of houses have been destroyed or are to be demolished and extensive repairs are needed for infrastructure to over 100,000 homes. As many as 8,900 people simply abandoned their homes and left the city in the first few months after the February event (Newell, 2012), and as many as 50,000 may leave during 2012. In particular, young whānau and single young women comprised a disproportionate number of these migrants, with evidence of a general movement to the North Island.
Te Puni Kōkiri sought a mix of quantitative and qualitative research to examine the social and economic impacts of the Christchurch earthquakes on Māori and their whānau. The result of this work will be a collection of evidence to inform policy to support and assist Māori and their whānau during the recovery/rebuild phases. To that end, this report triangulates available statistical and geographical information with qualitative data gathered over 2010 and 2011 by a series of interviews conducted with Māori who experienced the dramatic events associated with the earthquakes.
A Māori research team at Lincoln University was commissioned to undertake the research as they were already engaged in transdisciplinary research (began in the May 2010), that focused on quickly gathering data from a range of Māori who experienced the disaster, including relevant economic, environmental, social and cultural factors in the response and recovery of Māori to these events.
Participants for the qualitative research were drawn from Māori whānau who both stayed and left the city. Further data was available from ongoing projects and networks that the Lincoln research team was already involved in, including interviews with Māori first responders and managers operating in the CBD on the day of the February event. Some limited data is also available from younger members of affected whānau.
Māori in Ōtautahi/Christchurch City have exhibited their own culturally-attuned collective responses to the disaster. However, it is difficult to ascertain Māori demographic changes due to a lack of robust statistical frameworks but Māori outward migration from the city is estimated to range between 560 and 1,100 people.
The mobility displayed by Māori demonstrates an important but unquantified response by whānau to this disaster, with emigration to Australia presenting an attractive option for young Māori, an entrenched phenomenon that correlates to cyclical downturns and the long-term decline of the New Zealand economy. It is estimated that at least 315 Māori have emigrated from the Canterbury region to Australia post-quake, although the disaster itself may be only one of a series of events that has prompted such a decision.
Māori children made up more than one in four of the net loss of children aged 6 to 15 years enrolled in schools in Greater Christchurch over the year to June 2011. Research literature identifies depression affecting a small but significant number of children one to two years post-disaster and points to increasing clinical and organisational demands for Māori and other residents of the city.
For those residents in the eastern or coastal suburbs – home to many of the city’s Māori population - severe damage to housing, schools, shops, infrastructure, and streets has meant disruption to their lives, children’s schooling, employment, and community functioning. Ongoing abandonment of homes by many has meant a growing sense of unease and loss of security, exacerbated by arson, burglaries, increased drinking, a stalled local and national economy, and general confusion about the city’s future.
Māori cultural resilience has enabled a considerable network of people, institutions, and resources being available to Māori , most noticeably through marae and their integral roles of housing, as a coordinating hub, and their arguing for the wider affected communities of Christchurch.
Relevant disaster responses need to be discussed within whānau, kōhanga, kura, businesses, communities, and wider neighbourhoods. Comprehensive disaster management plans need to be drafted for all iwi in collaboration with central government, regional, and city or town councils.
Overall, Māori are remarkably philosophical about the effects of the disaster, with many proudly relishing their roles in what is clearly a historic event of great significance to the city and country. Most believe that ‘being Māori’ has helped cope with the disaster, although for some this draws on a collective history of poverty and marginalisation, features that contribute to the vulnerability of Māori to such events.
While the recovery and rebuild phases offer considerable options for Māori and iwi, with Ngāi Tahu set to play an important stakeholder in infrastructural, residential, and commercial developments, some risk and considerable unknowns are evident. Considerable numbers of Māori may migrate into the Canterbury region for employment in the rebuild, and trades training strategies have already been established.
With many iwi now increasingly investing in property, the risks from significant earthquakes are now more transparent, not least to insurers and the reinsurance sector. Iwi authorities need to be appraised of insurance issues and ensure sufficient coverage exists and investments and developments are undertaken with a clear understanding of the risks from natural hazards and exposure to future disasters.
Group case study report prepared for lecturers Ton Buhrs and Roy Montgomery by students of ERST 635 at Lincoln University, 2013.The New Zealand Government’s decision to establish a unitary authority in the Auckland Region has provided much of the context and impetus for this review of current governance arrangements in the Canterbury region, to determine whether or not they are optimal for taking the communities of greater Christchurch into the future. A number of local governance academics, as well as several respected political pundits, have prophesised that the Auckland ‘Super City’ reforms of 2009 will have serious implications and ramifications for local governance arrangements in other major cities, particularly Wellington and Christchurch. Wellington councils have already responded to the possibility of change by undertaking a series of reports on local governance arrangements, as well as a major review led by Sir Geoffrey Palmer, to investigate options for governance reform. Alongside these developments, the Christchurch earthquakes beginning in September 2010 have raised a myriad of new and complex governance issues, which may or may not be able to be addressed under the status quo, while the replacement of Regional Councillors’ with centrally-appointed Commissioners is suggestive of government dissatisfaction with current arrangements. With these things in mind, the research group has considered local government in Canterbury and the greater Christchurch area in the wider governance context. It does not limit discussion to only the structure of local government in Canterbury but rather, as the brief (Appendix 1) indicates, considers more broadly the relationship between central, regional, and local tiers of government, as well as the relationship between local government and local communities.
Throughout 2010 and 2011, the city of Christchurch, New Zealand, suffered a series of devastating earthquakes that caused serious damage to the city. This study examines the effect these earthquakes have had on the sport of swimming in Christchurch. It specifically focuses on three different aspects of the swimming industry: indoor competitive swimming, open water swimming and learning to swim. It reports on the industry prior to the earthquakes before examining the developments subsequent to the shakes. The effects on both facilities and participation numbers were examined. Results showed that many indoor swimming facilities were lost which had significant flow-on effects. In addition, many beaches were out of bounds and almost half of the schools in Canterbury lost the use of their own swimming pools. In terms of participation numbers, results showed that while there was a decrease in the number of indoor competitive swimmers, Canterbury clubs were still highly competitive and their rankings at events either remained similar or bettered during and after the period of the earthquakes. On the other hand, an increase in the number of participants was seen in swimming lessons as temporary pools were constructed and subsidies were offered to cover transport and lesson costs. Open water swimming, however, seems to have been relatively unaffected by the earthquakes.This report was made possible through Lincoln University’s Summer Scholarship programme. The authors would also like to acknowledge those anonymous interviewees who provided some valuable insight into the swimming industry in Christchurch.
The Canterbury region of New Zealand was shaken by major earthquakes on the 4th September 2010 and 22nd February 2011. The quakes caused 185 fatalities and extensive land, infrastructure and building damage, particularly in the Eastern suburbs of Christchurch city. Almost 450 ha of residential and public land was designated as a ‘Red Zone’ unsuitable for residential redevelopment because land damage was so significant, engineering solutions were uncertain, and repairs would be protracted. Subsequent demolition of all housing and infrastructure in the area has left a blank canvas of land stretching along the Avon River corridor from the CBD to the sea.
Initially the Government’s official – but enormously controversial – position was that this land would be cleared and lie fallow until engineering solutions could be found that enabled residential redevelopment. This paper presents an application of a choice experiment (CE) that identified and assessed Christchurch residents’ preferences for different land use options of this Red Zone. Results demonstrated strong public support for the development of a recreational reserve comprising a unique natural environment with native fauna and flora, healthy wetlands and rivers, and recreational opportunities that align with this vision. By highlighting the value of a range of alternatives, the CE provided a platform for public participation and expanded the conversational terrain upon which redevelopment policy took place. We conclude the method has value for land use decision-making beyond the disaster recovery context.
Globally, the maximum elevations at which treelines are observed to occur coincide with a 6.4 °C soil isotherm. However, when observed at finer scales, treelines display a considerable degree of spatial complexity in their patterns across the landscape and are often found occurring at lower elevations than expected relative to the global-scale pattern. There is still a
lack of understanding of how the abiotic environment imposes constraints on treeline patterns, the scales at which different effects are acting, and how these effects vary over large spatial extents. In this thesis, I examined abrupt Nothofagus treelines across seven degrees of
latitude in New Zealand in order to investigate two broad questions: (1) What is the nature and extent of spatial variability in Nothofagus treelines across the country? (2) How is this variation associated with abiotic variation at different spatial scales? A range of GIS, statistical, and atmospheric modelling methods were applied to address these two questions.
First, I characterised Nothofagus treeline patterns at a 15x15km scale across New Zealand using a set of seven, GIS-derived, quantitative metrics that describe different aspects of treeline position, shape, spatial configuration, and relationships with adjacent vegetation.
Multivariate clustering of these metrics revealed distinct treeline types that showed strong spatial aggregation across the country. This suggests a strong spatial structuring of the abiotic environment which, in turn, drives treeline patterns. About half of the multivariate treeline
metric variation was explained by patterns of climate, substrate, topographic and disturbance variability; on the whole, climatic and disturbance factors were most influential.
Second, I developed a conceptual model that describes how treeline elevation may
vary at different scales according to three categories of effects: thermal modifying effects, physiological stressors, and disturbance effects. I tested the relevance of this model for Nothofagus treelines by investigating treeline elevation variation at five nested scales (regional to local) using a hierarchical design based on nested river catchments. Hierarchical linear modelling revealed that the majority of the variation in treeline elevation resided at the broadest, regional scale, which was best explained by the thermal modifying effects of solar radiation, mountain mass, and differences in the potential for cold air ponding. Nonetheless, at finer scales, physiological and disturbance effects were important and acted to modify the regional trend at these scales. These results suggest that variation in abrupt treeline elevations
are due to both broad-scale temperature-based growth limitation processes and finer-scale stress- and disturbance-related effects on seedling establishment.
Third, I explored the applicability of a meso-scale atmospheric model, The Air
Pollution Model (TAPM), for generating 200 m resolution, hourly topoclimatic data for
temperature, incoming and outgoing radiation, relative humidity, and wind speeds. Initial assessments of TAPM outputs against data from two climate station locations over seven years showed that the model could generate predictions with a consistent level of accuracy for both sites, and which agreed with other evaluations in the literature. TAPM was then used to generate data at 28, 7x7 km Nothofagus treeline zones across New Zealand for January
(summer) and July (winter) 2002. Using mixed-effects linear models, I determined that both
site-level factors (mean growing season temperature, mountain mass, precipitation,
earthquake intensity) and local-level landform (slope and convexity) and topoclimatic factors (solar radiation, photoinhibition index, frost index, desiccation index) were influential in
explaining variation in treeline elevation within and among these sites. Treelines were
generally closer to their site-level maxima in regions with higher mean growing season
temperatures, larger mountains, and lower levels of precipitation. Within sites, higher
treelines were associated with higher solar radiation, and lower photoinhibition and
desiccation index values, in January, and lower desiccation index values in July. Higher treelines were also significantly associated with steeper, more convex landforms.
Overall, this thesis shows that investigating treelines across extensive areas at multiple study scales enables the development of a more comprehensive understanding of treeline variability and underlying environmental constraints. These results can be used to formulate new hypotheses regarding the mechanisms driving treeline formation and to guide the optimal choice of field sites at which to test these hypotheses.
Mixed conifer, beech and hardwood forests are relatively common in Aotearoa/New
Zealand, but are not well studied. This thesis investigates the coexistence, regeneration
dynamics and disturbance history of a mixed species forest across an environmental
gradient of drainage and soil development in north Westland.
The aim was to investigate whether conifers, beech and non-beech hardwood species were
able to coexist on surfaces that differed in their underlying edaphic conditions, and if so to understand the mechanisms that influenced their regeneration on both poorly drained and
well drained soils. The site selected was an area of high tree species diversity on a lowland
0.8 km² post-glacial terrace at the base of Mount Harata in the Grey River Valley.
My approach was to use forest stand history reconstruction at two spatial scales: an
intensive within-plot study of stand dynamics (chapter 1) and a whole-landform approach
(chapter 2) that examined whether the dynamics identified at the smaller within-plot scale
reflected larger patterns across the terrace.
In chapter 1, three large permanent plots (0.3-0.7 ha) were placed at different points along
the drainage gradient, one plot situated in each of the mainly well-drained, poorly drained
and very poorly drained areas along the terrace. Information was gathered on species age
and size structures, spatial distributions of tree ages, species interactions, microsite
establishment preferences, patterns of stand mortality, and disturbance history in each plot.
There were differences in stand structure, composition and relative abundance of species
found between the well drained plot and the two poorer drained plots. On the well drained
site conifers were scarce, the beeches Nothofagus fusca and N. menziesii dominated the
canopy, and in the subcanopy the hardwood species Weinmannia racemosa and Quintinia
acutifolia were abundant. As drainage became progressively poorer, the conifers
Dacrydium cupressinum and Dacrycarpus dacrydioides became more abundant and
occupied the emergent tier over a beech canopy. The hardwoods W. racemosa and Q.
acutifolia became gradually less abundant in the subcanopy, whereas the hardwood
Elaeocarpus hookerianus became more so.
In the well drained plot, gap partitioning for light between beeches and hardwoods enabled
coexistence in response to a range of different sized openings resulting from disturbances
of different extent. In the two more poorly drained plots, species also coexisted by
partitioning microsite establishment sites according to drainage.
There were several distinct periods where synchronous establishment of different species
occurred in different plots, suggesting there were large disturbances: c. 100yrs, 190-200
yrs, 275-300 yrs and 375-425 yrs ago. Generally after the same disturbance, different
species regenerated in different plots reflecting the underlying drainage gradient. However,
at the same site after different disturbances, different sets of species regenerated,
suggesting the type and extent of disturbances and the conditions left behind influenced
species regeneration at some times but not others. The regeneration of some species (e.g.,
N. fusca in the well-drained plot, and Dacrydium in the poorer drained plots) was periodic
and appeared to be closely linked to these events. In the intervals between these
disturbances, less extensive disturbances resulted in the more frequent N. menziesii and
especially hardwood regeneration. The type of tree death caused by different disturbances
favoured different species, with dead standing tree death favouring the more shade-tolerant
N. menziesii and hardwoods, whereas uprooting created a mosaic of microsite conditions
and larger gap sizes that enabled Dacrycarpus, N. fusca and E. hookerianus to maintain
themselves in the poorly drained areas.
In chapter 2, 10 circular plots (c. 0.12 ha) were placed in well drained areas and 10
circular plots (c. 0.2 ha) in poorly drained plots to collect information on species
population structures and microsite preferences. The aims were to reconstruct species'
regeneration responses to a range of disturbances of different type and extent across the
whole terrace, and to examine whether there were important differences in the effects of
these disturbances.
At this landform scale, the composition and relative abundances of species across the
drainage gradient reflected those found in chapter 1. There were few scattered conifers in well drained areas, despite many potential regeneration opportunities created from a range
of different stand destroying and smaller scale disturbances.
Three of the four periods identified in chapter 1 reflected distinct terrace-wide periods of
regeneration 75-100 yrs, 200-275 yrs and 350-450 yrs ago, providing strong evidence of
periodic large, infrequent disturbances that occurred at intervals of 100-200 yrs. These
large, infrequent disturbances have had a substantial influence in determining forest
history, and have had long term effects on forest structure and successional processes.
Different large, infrequent disturbances had different effects across the terrace, with the
variability in conditions that resulted enabling different species to regenerate at different
times. For example, the regeneration of distinct even-aged Dacrydium cohorts in poorly
drained areas was linked to historical Alpine Fault earthquakes, but not to more recent
storms. The variation in the intensity of different large, infrequent disturbances at different
points along the environmental drainage gradient, was a key factor influencing the scale of
impacts. In effect, the underlying edaphic conditions influenced species composition along
the drainage gradient and disturbance history regulated the relative abundances of species.
The results presented here further emphasise the importance of large scale disturbances as a
mechanism that allows coexistence of different tree species in mixed forest, in particular
for the conifers Dacrydium, Dacrycarpus and the beech N. fusca, by creating much of the
environmental variation to which these species responded. This study adds to our
understanding of the effects of historical earthquakes in the relatively complex forests of
north Westland, and further illustrates their importance in the Westland forest landscape as
the major influential disturbance on forest pattern and history.
These results also further develop the 'two-component' model used to describe
conifer/angiosperm dynamics, by identifying qualitative differences in the impacts of
different large, infrequent disturbances across an environmental gradient that allowed for
coexistence of different species. In poorer drained areas, these forests may even be thought
of as 'three-component' systems with conifers, beeches and hardwoods exhibiting key
differences in their regeneration patterns after disturbances of different type and extent, and
in their microsite preferences.
The major earthquakes of 2010 and 2011 brought to an abrupt end a process of adaptive reuse, revitalisation and gentrification that was underway in the early 20th century laneways and buildings located in the south eastern corner of the Christchurch Central Business District. Up until then, this location was seen as an exemplar of how mixed use could contribute to making the central city an attractive and viable alternative to the suburban living experience predominant in New Zealand.
This thesis is the result of a comprehensive case study of this “Lichfield Lanes” area, which involved in depth interviews with business owners, observation of public meetings and examination of documents and the revitalisation research literature. Findings were that many of the factors seen to make this location successful pre-earthquakes mirror the results of similar research in other cities. These factors include: the importance of building upon historic architecture and the eclectic spaces this creates; a wide variety of uses generating street life; affordable rental levels; plus the dangers of uniformity of use brought about by focussing on business types that pay the most rent. Also critical is co-operation between businesses to create and effectively market and manage an identifiable precinct that has a coherent style and ambience that differentiates the location from competing suburban malls. In relation to the latter, a significant finding of this project was that the hospitality and retail businesses key to the success of Lichfield Lanes were not typical and could be described as quirky, bohemian, chaotic, relatively low rent, owner operated and appealing to the economically important “Creative Class” identified by Richard Florida (2002) and others. In turn, success for many of these businesses can be characterised as including psychological and social returns rather than simply conventional economic benefits. This has important implications for inner city revitalisation, as it contrasts with the traditional focus of local authorities and property developers on physical aspects and tenant profitability as measures of success. This leads on to an important conclusion from this research, which is that an almost completely inverted strategy from that applied to suburban mall development, may be most appropriate for successful inner city revitalisation. It also highlights a disconnection between the focus and processes of regulatory authorities and the outcomes and processes most acceptable to the people likely to frequent the central city. Developers are often caught in the middle of this conflicted situation. Another finding was early commitment by businesses to rebuild the case study area in the same style, but over time this waned as delay, demolition, insurance problems, political and planning uncertainty plus other issues made participation by the original owners and tenants impossible or uneconomic. In conclusion, the focus of inner city revitalisation is too often on buildings rather than the people that use them and what they now desire from the central city.
Mitigating the cascade of environmental damage caused by the movement of excess reactive nitrogen (N) from land to sea is currently limited by difficulties in precisely and accurately measuring N fluxes due to variable rates of attenuation (denitrification) during transport. This thesis develops the use of the natural abundance isotopic composition of nitrate (δ15N and δ18O of NO₃-) to integrate the spatialtemporal variability inherent to denitrification, creating an empirical framework for evaluating attenuation during land to water NO₃- transfers. This technique is based on the knowledge that denitrifiers kinetically discriminate against 'heavy' forms of both N and oxygen (O), creating a parallel enrichment in isotopes of both species as the reaction progresses. This discrimination can be quantitatively related to NO₃- attenuation by isotopic enrichment factors (εdenit). However, while these principles are understood, use of NO₃- isotopes to quantify denitrification fluxes in non-marine environments has been limited by, 1) poor understanding of εdenit
variability, and, 2) difficulty in distinguishing the extent of mixing of isotopically distinct sources from the
imprint of denitrification. Through a combination of critical literature analysis, mathematical modelling, mesocosm to field scale experiments, and empirical studies on two river systems over distance and time, these short comings are parametrised and a template for future NO₃- isotope based attenuation measurements
outlined.
Published εdenit values (n = 169) are collated in the literature analysis presented in Chapter 2. By evaluating these values in the context of known controllers on the denitrification process, it is found that the magnitude of εdenit, for both δ15N and δ18O, is controlled by, 1) biology, 2) mode of transport through the denitrifying zone (diffusion v. advection), and, 3) nitrification (spatial-temporal distance between nitrification and denitrification). Based on the outcomes of this synthesis, the impact of the three factors identified as controlling εdenit are quantified in the context of freshwater systems by combining simple mathematical modelling and lab incubation studies (comparison of natural variation in biological versus physical expression). Biologically-defined εdenit, measured in sediments collected from four sites along a temperate stream and from three tropical submerged paddy fields, varied from -3‰ to -28‰ depending on the site’s antecedent carbon content. Following diffusive transport to aerobic surface water, εdenit was found to
become more homogeneous, but also lower, with the strength of the effect controlled primarily by diffusive distance and the rate of denitrification in the sediments. I conclude that, given the variability in fractionation dynamics at all levels, applying a range of εdenit from -2‰ to -10‰ provides more accurate measurements of attenuation than attempting to establish a site-specific value. Applying this understanding of denitrification's fractionation dynamics, four field studies were conducted to measure denitrification/ NO₃- attenuation across diverse terrestrial → freshwater systems. The development of NO₃- isotopic signatures (i.e., the impact of nitrification, biological N fixation, and ammonia volatilisation on the isotopic 'imprint' of denitrification) were evaluated within two key agricultural regions: New Zealand grazed pastures (Chapter 4) and Philippine lowland submerged rice production (Chapter 5). By measuring the isotopic composition of soil ammonium, NO₃- and volatilised ammonia following the bovine urine deposition, it was determined that the isotopic composition of NO₃ - leached from grazed pastures is defined by the balance between nitrification and denitrification, not ammonia volatilisation. Consequently, NO₃- created within pasture systems was predicted to range from +10‰ (δ15N)and -0.9‰ (δ18O) for non-fertilised fields (N limited) to -3‰ (δ15N) and +2‰ (δ18O) for grazed fertilised fields (N saturated). Denitrification was also the dominant determinant of NO₃- signatures in the Philippine rice paddy. Using a site-specific εdenit for the paddy, N inputs versus attenuation were able to be calculated, revealing that >50% of available N in the top 10 cm of soil was denitrified during land preparation, and >80% of available N by two weeks post-transplanting. Intriguingly, this denitrification was driven by rapid
NO₃- production via nitrification of newly mineralised N during land preparation activities.
Building on the relevant range of εdenit established in Chapters 2 and 3, as well as the soil-zone confirmation that denitrification was the primary determinant of NO₃- isotopic composition, two long-term
longitudinal river studies were conducted to assess attenuation during transport. In Chapter 6, impact and recovery dynamics in an urban stream were assessed over six months along a longitudinal impact gradient using measurements of NO₃- dual isotopes, biological populations, and stream chemistry. Within 10 days of the catastrophic Christchurch earthquake, dissolved oxygen in the lowest reaches was <1 mg l⁻¹, in-stream denitrification accelerated (attenuating 40-80% of sewage N), microbial biofilm communities changed, and several benthic invertebrate taxa disappeared. To test the strength of this method for tackling the diffuse, chronic N loading of streams in agricultural regions, two years of longitudinal measurements of NO₃- isotopes were collected. Attenuation was negatively correlated with NO₃- concentration, and was highly
dependent on rainfall: 93% of calculated attenuation (20 kg NO₃--N ha⁻¹ y⁻¹) occurred within 48 h of rainfall.
The results of these studies demonstrate the power of intense measurements of NO₃- stable isotope for distinguishing temporal and spatial trends in NO₃ - loss pathways, and potentially allow for improved catchment-scale management of agricultural intensification. Overall this work now provides a more cohesive understanding for expanding the use of NO₃- isotopes measurements to generate accurate understandings of the controls on N losses. This information is becoming increasingly important to predict ecosystem response to future changes, such the increasing agricultural intensity needed to meet global food demand, which is occurring synergistically with unpredictable global climate change.
