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Research Papers, Lincoln University

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.

Research Papers, Lincoln University

The city of Christchurch, New Zealand, was until very recently a “Junior England”—a small city that still bore the strong imprint of nineteenth-century British colonization, alongside a growing interest in the underlying biophysical setting and the indigenous pre-European landscape. All of this has changed as the city has been subjected to a devastating series of earthquakes, beginning in September 2010, and still continuing, with over 12,000 aftershocks recorded. One of these aftershocks, on February 22, 2011, was very close to the city center and very shallow with disastrous consequences, including a death toll of 185. Many buildings collapsed, and many more need to be demolished for safety purposes, meaning that over 80 percent of the central city will have gone. Tied up with this is the city’s precious heritage—its buildings and parks, rivers, and trees. The threats to heritage throw debates over economics and emotion into sharp relief. A number of nostalgic positions emerge from the dust and rubble, and in one form is a reverse-amnesia—an insistence of the past in the present. Individuals can respond to nostalgia in very different ways, at one extreme become mired in it and unable to move on, and at the other, dismissive of nostalgia as a luxury in the face of more pressing crises. The range of positions on nostalgia represent the complexity of heritage debates, attachment, and identity—and the ways in which disasters amplify the ongoing discourse on approaches to conservation and the value of historic landscapes.

Research Papers, Lincoln University

Lincoln University was commissioned by the Avon-Otakaro Network (AvON) to estimate the value of the benefits of a ‘recreation reserve’ or ‘river park’ in the Avon River Residential Red Zone (ARRRZ). This research has demonstrated significant public desire and support for the development of a recreation reserve in the Avon River Residential Red Zone. Support is strongest for a unique natural environment with native fauna and flora, healthy wetlands and rivers, and recreational opportunities that align with this vision, such as walking, cycling and water-based sporting and leisure activities. The research also showed support for a reserve that promotes and enables community interaction and wellbeing, and is evident in respondents’ desires for community gardens, regular festivals and markets, and the physical linking of the CBD with eastern suburbs through a green corridor. There is less support for children’s playgrounds, sports fields or open grassed areas, all of which could be considered as more typical of an urban park development. Benefits (willing to pay) to Christchurch residents (excluding tourists) of a recreation reserve could be as high as $35 million each year. Savings to public health costs could be as high as $50.3 million each year. The incorporation or restoration of various ecosystems services, including water quality improvements, flood mitigation and storm water management could yield a further $8.8 million ($19, 600) per hectare/year at 450 ha). Combined annual benefits of a recreational reserve in the ARRRZ are approximately $94.1 million per annum but this figure does not include potentially significant benefits from, for example, tourism, property equity gains in areas adjacent to the reserve, or the effects of economic rejuvenation in the East. Although we were not able to provide costing estimates for park attributes, this study does make available the value of benefits, which can be used as a guide to the scope of expenditure on development of each park attribute.

Research Papers, Lincoln University

The earthquake swarm that has struck Canterbury, New Zealand from September 2010 has led to widespread destruction and loss of life in the city of Christchurch. In response to this the New Zealand government convened a Royal Commission under the Commissions of Inquiry Act 1908. The terms of reference for this enquiry were wide ranging, and included inquiry into legal and best-practice requirements for earthquake-prone buildings and associated risk management strategies. The Commission produced a final report on earthquake-prone buildings and recommendations which was made public on the 7th December 2012. Also on the 7th of December 2012 the Ministry of Business, Innovation and Employment (MBIE) released a Consultation Document that includes many of the recommendations put forward by the Royal Commission. This paper examines the evidence presented to the Royal Commission and reviews their recommendations and those of MBIE in relation to the management of earthquake-prone buildings. An analysis of the likely impacts of the recommendations and proposals on both the property market and society in general is also undertaken.

Research Papers, Lincoln University

The earthquakes that struck Ōtautahi/Christchurch began September 2010 and continued throughout2012 with the worse shock being February 22, 2011. The extended ‘seismic event’ radically altered thegeophysical and socio-cultural environments of the city. This working paper presents a broad array of datadescribing the impacts of the disaster on Māori. These data frame the results of small email surveyconducted 18 months after the most destructive February 22, 2011. This survey followed two projectsinvestigating the resilience of Māori to the disaster (Lambert & Mark-Shadbolt, 2011; Lambert & Mark-Shadbolt, 2012; Lambert, Mark-Shadbolt, Ataria, & Black, 2012). Results show that while the termresilience has become common to the point of cliché, the Māori experience thus far is best described asendurance.