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Research papers, Lincoln University

This thesis investigates landscape disturbance history in Westland since 1350 AD. Specifically, I test the hypothesis that large-magnitude regional episodes of natural disturbance have periodically devastated portions of the landscape and forest, and that these were caused by infrequent earthquakes along the Alpine Fault. Forest stand history reconstruction was used to determine the timing and extent of erosion and sedimentation events that initiated new forest cohorts in a 1412 ha study area in the Karangarua River catchment, south Westland. Over 85 % of the study area was disturbed sufficiently by erosion/sedimentation since 1350 AD to initiate new forest cohorts. During this time four episodes of catchment-wide disturbance impacted the study area, and these took place about 1825 AD ± 5 years (Ruera episode), 1715 AD ± 5 years (Sparkling episode), 1615 AD ± 5 years (McTaggart episode), and 1445 AD ± 15 years (Junction episode). The three most recent episodes disturbed 10 %, 35-40 % and 32-50 % respectively of the study area. The Junction episode disturbed at least 6 % of the study area, but elimination of evidence by more recent disturbances prevented an upper limit being defined. The three earliest episodes correspond to the date-ranges for three Alpine Fault earthquakes from geological data, and are the only episodes of disturbance within each date-range. An earthquake cause is also consistent with features of the disturbance record: large portions of the study area were disturbed, disturbance occurred on all types 'of landforms, and terrace surfaces were abandoned upstream of the Alpine Fault. On this basis erosion/sedimentation induced by Alpine Fault earthquakes has disturbed 14-20 % of the land surface in the study area per century. Storms and other non-seismic erosional processes have disturbed 3-4 % per century. To examine the importance of the Alpine Fault earthquakes to forest disturbance throughout Westland, I collated all available data on conifer stand age structures in the region and identified dates of disturbance events from 55 even-aged cohorts of trees. Three region-wide episodes of forest disturbance since 1350 AD were found in this sample, and these matched the three Alpine Fault earthquake-caused episodes found in the Karangarua. Forest disturbance at these times was widespread across Westland over at least 200 km from Paringa to Hokitika, and originated from both tree fall and erosion processes. This disturbance history can explain the long-observed regional conifer forest pattern in Westland, of a predominance of similar-sized stands of trees and a relative lack of small-sized (young) stands. The many similar-sized stands are a consequence of synchronous forest disturbance and re-establishment accompanying the infrequent Alpine Fault earthquakes, while the dominance of mature stands of trees and relative lack of young small-sized trees in stands is explained by the long lapsed time since the last Alpine Fault earthquake (c. 280 years). I applied the landscape disturbance history information to the existing geological data to reconstruct the paleoseismicity of the Alpine Fault since 1350 AD. Best estimates for the timing of the most recent three rupture events from these data are 1715 AD ± 5 years, 1615 AD ± 5 years and 1445 AD ± 15 years. Earthquake recurrence intervals were variable, ranging from about 100 years to at least 280 years (the lapsed time since the last event). All three events caused forest and geomorphic disturbance over at least a 200 km section of Fault between the Karangarua and Hokitika Rivers, and were probably single rupture events. Suppressions in cross dated tree-ring chronologies in the western South Island suggest that the last rupture occurred in 1717 AD, and extended as a single rupture from Haupiri to Fiordland, a distance along the Fault of 375 km.

Images, eqnz.chch.2010

Knox Church earthquake repair/rebuild on a walk around Christchurch December 11, 2013 New Zealand. www.stuff.co.nz/the-press/news/christchurch-earthquake-20... All about our ear...

Audio, Radio New Zealand

Topics - The Earthquake Recovery Minister, Gerry Brownlee, says it is important to be realistic about the demolition of Christchurch's heritage buildings following the powerful earthquake there last month. Motorists should prepare themselves for more increases in the price of petrol which, the AA warns, is likely to reach a new high.

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, Victoria University of Wellington

“One of the most basic and fundamental questions in urban master planning and building regulations is ‘how to secure common access to sun, light and fresh air?” (Stromann-Andersen & Sattrup, 2011).  Daylighting and natural ventilation can have significant benefits in office buildings. Both of these ‘passive’ strategies have been found to reduce artificial lighting and air-conditioning energy consumption by as much as 80% (Ministry for the Environment, 2008); (Brager, et al., 2007). Access to daylight and fresh air can also be credited with improved occupant comfort and health, which can lead to a reduction of employee absenteeism and an increase of productivity (Sustainability Victoria, 2008).  In the rebuild of Christchurch central city, following the earthquakes of 2010 and 2011, Cantabrians have expressed a desire for a low-rise, sustainable city, with open spaces and high performance buildings (Christchurch City Council, 2011). With over 80% of the central city being demolished, a unique opportunity to readdress urban form and create a city that provides all buildings with access to daylight and fresh air exists.  But a major barrier to wide-spread adoption of passive buildings in New Zealand is their dependence on void space to deliver daylight and fresh air – void space which could otherwise be valuable built floor space. Currently, urban planning regulations in Christchurch prioritize density, allowing and even encouraging low performance compact buildings.  Considering this issue of density, this thesis aimed to determine which urban form and building design changes would have the greatest effect on building performance in Central City Christchurch.  The research proposed and parametrically tested modifications of the current compact urban form model, as well as passive building design elements. Proposed changes were assessed in three areas: energy consumption, indoor comfort and density. Three computer programs were used: EnergyPlus was the primary tool, simulating energy consumption and thermal comfort. Radiance/Daysim was used to provide robust daylighting calculations and analysis. UrbaWind enabled detailed consideration of the urban wind environment for reliable natural ventilation predictions.  Results found that, through a porous urban form and utilization of daylight and fresh air via simple windows, energy consumption could be reduced as much as 50% in buildings. With automatic modulation of windows and lighting, thermal and visual comfort could be maintained naturally for the majority of the occupied year. Separation of buildings by as little as 2m enabled significant energy improvements while having only minimal impact on individual property and city densities.  Findings indicated that with minor alterations to current urban planning laws, all buildings could have common access to daylight and fresh air, enabling them to operate naturally, increasing energy efficiency and resilience.