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Research Papers, Lincoln University

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.

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

As far as suburbs with bad reputations go, Aranui in Christchurch often seems to dominate local public perceptions. High crime, high unemployment, low incomes, run-down state houses and uncared-for neighbourhoods have been the key words and phrases used over many decades. This reputation achieved national standing over the same period and in 2001 Aranui gained the dubious distinction of becoming the pilot project for the Labour Government’s state housing Community Renewal Programme initiated in 2001. It is common to read “Don’t buy or rent here” comments on websites and blogs advising prospective immigrants on where to live. One of the dispiriting moments in Aranui’s history came in September 2009 with the discovery of two bodies under the floorboards of a Hampshire Street property and the subsequent charge of double-homicide and conviction of local resident Jason Somerville for the murder of his wife Rebecca Chamberlain and neighbour Tisha Lowry.

Research Papers, Lincoln University

Since the 2010/11 Canterbury earthquakes, Akaroa has been hosting the majority of cruise ship arrivals to Canterbury. This amounts to approximately 70-74 days per season, when between 2,000- 4,000 persons come ashore between 9am and 4pm when in port. This increased level of cruise ship arrivals has had significant impacts, both beneficial and detrimental, on Akaroa. Attitudes within the Akaroa community to hosting cruise ship arrivals appear to be divided, and has led to public debate in Akaroa about the issue. In response to this situation, Christchurch and Canterbury Tourism (CCT) commissioned this research project to assess the impact of cruise ship tourism on the Akaroa community.This research was commissioned and funded by Christchurch and Canterbury Tourism (CCT).

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.

Images, UC QuakeStudies

A photograph of a floating installation on the Avon River. The installation consists of four chairs and a table situated on a grass-covered platform. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of four chairs and a table situated on a grass-covered platform. It was created by students from Lincoln University's School of Landscape Architecturefor Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of four chairs and a table situated on a grass-covered platform. It was created by students from Lincoln University's School of Landscape Architecturefor Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of dresser, stool and lamp, situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation on the Avon River. The installation consists of two armchairs, a table and a floor lamp situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of a floor lamp, dresser and stool situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of painted bird cut-outs hanging from a tree next to the Avon River on Oxford Terrace, near the Worcester Street bridge. The decorations were part of an installation titled The River, created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of four chairs and a table situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of two armchairs, a table and floor lamp situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecturefor Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of painted bird cut-outs hanging from a tree next to the Avon River on Oxford Terrace, near the Worcester Street bridge. The decorations were part of an installation titled The River, created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation on the Avon River. The installation consists of four chairs and a table situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation on the Avon River. The installation consists of dresser, stool and lamp, situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A close-up photograph of a floating installation titled The River on the Avon River. The installation consists of four chairs and a table situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of one of several painted bird cut-outs hanging from a tree next to the Avon River on Oxford Terrace, near the Worcester Street bridge. The decorations were part of an installation titled The River, created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of two armchairs, a table and a floor lamp situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of two armchairs, a table and a floor lamp situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of two armchairs, a table and a floor lamp situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of two armchairs, a table and a floor lamp situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of a floor lamp, dresser and stool situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation on the Avon River as part of Canterbury Tales. The installation consists of a floor lamp, dresser and stool situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River on the Avon River. The installation consists of two chairs, a lamp and a table, situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.

Images, UC QuakeStudies

A photograph of a floating installation titled The River, on the Avon River. The installation consists of four chairs and a table situated on a grass-covered platform, with net curtains hanging from the frame. It was created by students from Lincoln University's School of Landscape Architecture for Canterbury Tales, a carnivalesque procession and the main event of FESTA 2013.