Carbon dynamics in apple orchards in New Zealand and their integration into life cycle assessment : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Ph.D) in Soil Sciences and Life Cycle Management

Soil carbon sequestration can help mitigate climate change and soil carbon contributes to many of the ecosystem services provided by the soil; thus soil carbon contributes to the sustainability of food production systems. However, changes in soil carbon are difficult and costly to measure due to two constraining characteristics: the spatial variability of the stocks as well as the typically small changes in carbon stocks over time. Consequently, environmental assessment tools such as Life Cycle Assessment (LCA) and carbon footprinting (CF) generally exclude the changes in soil carbon stocks from their analyses. Yet global supermarket chains use the results from these tools to inform consumers about greener products. In New Zealand (NZ), production of horticultural products such as apples is very focussed on export markets. Therefore, if it can be demonstrated that the production of New Zealand apples maintains or increases the carbon stock of the orchard soil and above-ground biomass, this could lead to a reduced net CF and might enhance access to prime retailers’ shelves in major export markets. The main aims of this research were (a) to develop a practical method for measuring a statistically significant and powerful change in the soil-carbon stock of an apple orchard block in New Zealand, and (b) to assess a method to estimate the standing woody biomass carbon stock in apple orchards, in order to provide reliable data for the CF of NZ apples. Since there are no data available, this research sought to quantify the changes in soil-carbon stocks in apple orchards by means of a chrono-sequence. A review of LCA and CF case studies accounting for changes in soil-carbon identified the need to focus on collecting deep, site specific, geo-localised and time-dependent soil-carbon data, as well as communicating its variability and statistical uncertainty for interpretation and transparency of LCA and CF results. Therefore, in a first step to develop a protocol for quantifying the carbon stocks in the soil, a four-year-old apple orchard block was intensively sampled to one meter depth to measure the soil-carbon stock and the spatial patterns. It was found that the soil-carbon stock was influenced by tree planting pattern, and the minimum sampling requirements were determined to detect, from sampling every 20 years, a change of the mean (175.1± 10.8 t C/ha) of 10 % due to the spatial and temporal characteristics of soil carbon. This required sampling nine sites in a systematic grid in the orchard block, with four pooled samples per site evenly distributed between and outside the wheel tracks, at a total cost of NZ$1,590 per sampling campaign. This cost of monitoring seems affordable as it is equivalent to just 0.5premiums could compensate for it, using the carbon market seems unrealistic at present because the price of carbon would need to reach at least NZ$182/tonne. To inform development of a protocol for quantifying the carbon stocks in the woody biomass in a commercial apple orchard block, the relationship between the trunk cross-sectional area (TCA) and the woody dry mass (DM) of the trees was assessed using 10 trees that were destructively harvested. It was found that using this relationship together with a high number of TCAs measured in situ in the orchard block facilitated the rapid and cost effective estimation of the woody biomass carbon stocks at the orchard block scale. At the end of the orchard life, the carbon has been stored out of the atmosphere for the lifetime of the trees and this contributes to reduced climate change. Furthermore, at the end of life the trees may be burned for convenience, chopped for firewood or transformed into biochar and applied to soils. It was found that the biochar scenario provided the largest reduction, and that this benefit was equivalent to 0.7% of the carbon footprint of apples exported to Europe. The choice of a time horizon for the assessment was found to be critical, with comparative results varying up to three fold between the 20 year and the 100 year time horizons. Regarding changes in soil carbon stocks over time, the four-year-old orchard block was part of a 12 year-old chronosequence, also including a one-year, a six-year and a twelve-year old block. The same sampling protocol was carried out in these three other blocks. It was found that all orchard blocks had relatively high soil-carbon stocks. Moreover, there was no significant difference in soil-carbon stocks at the 5% level between the one-year-old, the six-year-old and the twelve-year-old blocks of the chronosequence. Based on the soil-carbon stocks of these three blocks, current management practices seem to be maintaining these carbon stocks over time. Therefore, unless management practices are modified, monitoring may not be required. However, this maintenance of relatively high soil-carbon stocks in orchard systems is beneficial for climate change and the ecosystem services provided by the soil. It should therefore be treated as such in LCA and CF studies although a method is yet to be developed. In addition, despite a high similarity with the other blocks, the four-year-old block showed a higher, significantly different soil-carbon stock, and the levels of variability in soil-carbon stocks were found to be different between all the blocks. This demonstrates the high local specificity of soil-carbon stocks. The six year-old block displayed a coefficient of variation (14%) larger than the other blocks, and so an analysis of sampling requirements was conducted for this block. A change of 10% of the mean could, in theory, be observed by collecting a total of 78 samples, bulked two by two, for carbon content, and using 39 bulk density profiles, all to one meter depth. The associated cost of monitoring is NZ$ 9,420 and is equivalent to 1% of the value of export apples at ship-side in New Zealand. Monitoring soil-carbon stocks would seem therefore affordable, even in the more variable orchard block. Overall, this research has made four main contributions to the science. Firstly, a robust, practical and adaptable protocol for monitoring soil-carbon stocks in apple orchards has been developed. Secondly, a rapid and cost effective method to estimate the carbon stock in standing woody biomass has been verified for use in commercial apple orchard blocks; accounting for this biomass carbon stock may lead to a net reduction of up to 4.6% of the New Zealand based (cradle to NZ port) CF of apples exported to Europe; Thirdly, a chrono-sequence of orchard blocks has suggested that current management practices in apple orchards appear to achieve the maintenance of high soil-carbon stocks over time, and it is suggested that this maintenance should be recognised as beneficial in CF and LCA studies. Finally, soil carbon stocks have been found to be spatially variable within and between similar orchard blocks; therefore LCA and CF studies should use site specific data and communicate the uncertainty of their soil-carbon stock estimates

Unsupervised decoding of long-term, naturalistic human neural recordings with automated video and audio annotations

Fully automated decoding of human activities and intentions from direct neural recordings is a tantalizing challenge in brain-computer interfacing. Most ongoing efforts have focused on training decoders on specific, stereotyped tasks in laboratory settings. Implementing brain-computer interfaces (BCIs) in natural settings requires adaptive strategies and scalable algorithms that require minimal supervision. Here we propose an unsupervised approach to decoding neural states from human brain recordings acquired in a naturalistic context. We demonstrate our approach on continuous long-term electrocorticographic (ECoG) data recorded over many days from the brain surface of subjects in a hospital room, with simultaneous audio and video recordings. We first discovered clusters in high-dimensional ECoG recordings and then annotated coherent clusters using speech and movement labels extracted automatically from audio and video recordings. To our knowledge, this represents the first time techniques from computer vision and speech processing have been used for natural ECoG decoding. Our results show that our unsupervised approach can discover distinct behaviors from ECoG data, including moving, speaking and resting. We verify the accuracy of our approach by comparing to manual annotations. Projecting the discovered cluster centers back onto the brain, this technique opens the door to automated functional brain mapping in natural settings

AMPTE/CCE‐SCATHA simultaneous observations of substorm‐associated magnetic fluctuations

This study examines substorm-associated magnetic field fluctuations observed by the AMPTE/CCE and SCATHA satellites in the near-Earth tail. Three tail reconfiguration events are selected, one event on August 28, 1986, and two consecutive events on August 30, 1986. The fractal analysis was applied to magnetic field measurements of each satellite. The result indicates that (1) the amplitude of the fluctuation of the north-south magnetic component is larger, though not overwhelmingly, than the amplitudes of the other two components and (2) the magnetic fluctuations do have a characteristic timescale, which is several times the proton gyroperiod. In the examined events the satellite separation was less than 10 times the proton gyroradius. Nevertheless, the comparison between the AMPTE/CCE and SCATHA observations indicates that (3) there was a noticeable time delay between the onsets of the magnetic fluctuations at the two satellite positions, which is too long to ascribe to the propagation of a fast magnetosonic wave, and (4) the coherence of the magnetic fluctuations was low in the August 28, 1986, event and the fluctuations had different characteristic timescales in the first event of August 30, 1986, whereas some similarities can be found for the second event of August 30, 1986. Result 1 indicates that perturbation electric currents associated with the magnetic fluctuations tend to flow parallel to the tail current sheet and are presumably related to the reduction of the tail current intensity. Results 2 and 3 suggest that the excitation of the magnetic fluctuations and therefore the trigger of the tail current disruption is a kinetic process in which ions play an important role. It is inferred from results 3 and 4 that the characteristic spatial scale of the associated instability is of the order of the proton gyroradius or even shorter, and therefore the tail current disruption is described as a system of chaotic filamentary electric currents. However, result 4 suggests that the nature of the tail current disruption can vary from event to event

Laser-induced isotopic selectivity in the resonance ionization of Os

Isotope selective effects in resonance ionization mass spectrometry (RIMS) pose a potentially serious limitation to the application of this technique to the precise and reproducible measurement of isotope ratios. In order to identify some of the underlying causes of isotope selectivity in RIMS and to establish procedures for minimizing these effects, we investigated laser-induced isotope selectivity in the resonance ionization of Os. A single-color, one-photon resonant ionization scheme was used for several different transitions to produce Os photoions from a thermal atomization source. Variations in Os isotope ratios were studied as a function of laser parameters such as wavelength, bandwidth, power and polarization state. Isotope selectivity is strongly dependent on laser power and wavelength, even when the bandwidth of the laser radiation is much larger than the optical isotope shift. Variations in the ^(190)Os/^(188)Os ratio of ≈20% for a detuning of 0.8 cm^(−1) were observed on a transition with a small oscillator strength. Large even—odd isotope selectivity with a 13% depletion of ^(189)Os was observed on a ΔJ = +1 transition at low laser intensity; the odd mass Os isotopes are systematically depleted. For ΔJ = −1 and 0 transitions the isotope selectivity was reduced by polarization scrambling and for strongly saturating conditions. A technique employing the wavelength dependence of even—even isotope selectivity as an internal wavelength standard was developed to permit accurate and reproducible wavelength adjustment of the laser radiation. This technique provides control over laser-induced isotope selectivity for single-color ionization and enabled us to obtain reproducible measurements of ^(192)Os/^(188)Os and ^(189)Os/^(190)Os ratios in the saturation regime for a ΔJ = +1 transition with a precision of better than 0.5%. The application of this wavelength-tuning procedure should significantly improve the quality of RIMS isotope ratio data for many elements

Controls on the diurnal streamflow cycles in two subbasins of an alpine headwater catchment

In high-altitude alpine catchments, diurnal streamflow cycles are typically dominated by snowmelt or ice melt. Evapotranspiration-induced diurnal streamflow cycles are less observed in these catchments but might happen simultaneously. During a field campaign in the summer 2012 in an alpine catchment in the Swiss Alps (Val Ferret catchment, 20.4 km2, glaciarized area: 2%), we observed a transition in the early season from a snowmelt to an evapotranspiration-induced diurnal streamflow cycle in one of two monitored subbasins. The two different cycles were of comparable amplitudes and the transition happened within a time span of several days. In the second monitored subbasin, we observed an ice melt-dominated diurnal cycle during the entire season due to the presence of a small glacier. Comparisons between ice melt and evapotranspiration cycles showed that the two processes were happening at the same times of day but with a different sign and a different shape. The amplitude of the ice melt cycle decreased exponentially during the season and was larger than the amplitude of the evapotranspiration cycle which was relatively constant during the season. Our study suggests that an evapotranspiration-dominated diurnal streamflow cycle could damp the ice melt-dominated diurnal streamflow cycle. The two types of diurnal streamflow cycles were separated using a method based on the identification of the active riparian area and measurement of evapotranspiration

Bounds on gravitational wave backgrounds from large distance clock comparisons

Our spacetime is filled with gravitational wave backgrounds that constitute a fluctuating environment created by astrophysical and cosmological sources. Bounds on these backgrounds are obtained from cosmological and astrophysical data but also by analysis of ranging and Doppler signals from distant spacecraft. We propose here a new way to set bounds on those backgrounds by performing clock comparisons between a ground clock and a remote spacecraft equipped with an ultra-stable clock, rather than only ranging to an onboard transponder. This technique can then be optimized as a function of the signal to be measured and the dominant noise sources, leading to significant improvements on present bounds in a promising frequency range where different theoretical models are competing. We illustrate our approach using the SAGAS project which aims to fly an ultra stable optical clock in the outer solar system.Comment: 10 pages, 8 figures, minor amendment

The XMM-Newton view of the Crab

Aims. We discuss the current X-ray view of the Crab Nebula and Pulsar, summarising our analysis of observations of the source with the EPIC-pn camera on board the XMM-Newton observatory. Different modes of EPIC-pn were combined in order to yield a complete scenario of the spectral properties of the Crab resolved in space and time (pulse phase). In addition we give a description of the special EPIC-pn Burst mode and guidance for data reduction in that mode. Methods. We analysed spectra for the nebula and pulsar separately in the 0.6−12.0 keV energy band. All data were processed with the SAS 6.0.0 XMM-Newton Scientific Analysis System package; models were fitted to the data with XSPEC 11. The high time resolution of EPIC-pn in its Burst mode (7 μs) was used for a phase resolved analysis of the pulsar spectrum, after determination of the period with epoch folding techniques. Data from the SmallWindow mode were processed and corrected for pile-up allowing for spectroscopy simultaneously resolved in space and time. Results. The spatial variation of the spectrum over the entire region of the Crab shows a gradual spectral softening from the inner pulsar region to the outer nebula region with a variation in photon index, Γ, from 2.0 to 2.4. Pulse phase resolved spectroscopy of the Crab Pulsar reveals a phase dependent modulation of the photon index in form of a significant hardening of the spectrum in the inter-peak phase from Γ = 1.7 during the pulse peak to Γ = 1.5

Voltage noise analysis with ring oscillator clocks

Voltage noise is the main source of dynamic variability in integrated circuits and a major concern for the design of Power Delivery Networks (PDNs). Ring Oscillators Clocks (ROCs) have been proposed as an alternative to mitigate the negative effects of voltage noise as technology scales down and power density increases. However, their effectiveness highly depends on the design parameters of the PDN, power consumption patterns of the system and spatial locality of the ROCs within the clock domains. This paper analyzes the impact of the PDN parameters and ROC location on the robustness to voltage noise. The capability of reacting instantaneously to unpredictable voltage droops makes ROCs an attractive solution, which allows to reduce the amount of decoupling capacitance without downgrading performance. Tolerance to voltage noise and related benefits can be increased by using multiple ROCs and reducing the size of the clock domains. The analysis shows that up to 83% of the margins for voltage noise and up to 27% of the leakage power can be reduced by using local ROCs.Peer ReviewedPostprint (author's final draft