10,277 results for ResearchCommons@Waikato

  • Dewfall as a water source frequently activates the endolithic cyanobacterial communities in the granites of Taylor Valley, Antarctica

    Büdel, Burkhard; Bendix, Jörg; Bicker, Fritz R.; Green, T.G. Allan (2008)

    Journal article
    University of Waikato

    Endolithic photosynthetic microorganisms like cyanobacteria and algae are well known from savannas and deserts of the world, the high Arctic, and also Antarctic habitats like the Dry Valleys in the Ross Dependency. These endolithic microbial communities are thought to be at the limits of life with reported ages in the order of thousands of years. Here we report on an extensive chasmoendolithic cyanobacterial community inside granite rocks of Mt. Falconer in the lower Taylor Valley, Dry Valleys. On average, the cyanobacterial community was 4.49 ± 0.95 mm below the rock surface, where it formed a blue-green layer. The community was composed mainly of the cyanobacterium Chroococcidiopsis sp., with occasional Cyanothece cf. aeruginosa (Nägeli) Komárek and Nostoc sp. Mean biomass was 168 ± 44 g carbon • m⁻², and the mean chl a content was 24.3 ± 34.2 mg • m⁻². In situ chl fluorescence measurements—a relative measure of photosynthetic activity—showed that they were active over long periods each day and also showed activity the next day in the absence of any moisture. Radiocarbon dating gave a relatively young age (175–280 years) for the community. Calculations from microclimate data demonstrated that formation of dew or rime was possible and could frequently activate the cyanobacteria and may explain the younger age of microbial communities at Mt. Falconer compared to older and less active endolithic microorganisms reported earlier from Linnaeus Terrace, a higher altitude region that experiences colder, drier conditions.

    View record details
  • Water relations and CO₂ exchange of the terrestrial lichen Teloschistes capensis in the Namib fog desert: Measurements during two seasons in the field and under controlled conditions

    Lange, Otto L.; Green, T.G. Allan; Melzer, Beate; Meyer, Angelika; Zellner, Hans (2006)

    Journal article
    University of Waikato

    Although the coastal zone of the Central Namib Desert (Namibia) has negligible rainfall, frequent fog, dew and high air humidity support a luxurious lichen flora. Large areas of soil crust communities are dominated by the multibranched, fruticose Teloschistes capensis interspersed by a (still indeterminable) Ramalina species. In earlier communications, based on field measurements in autumn, we began the analysis of functional mechanisms that allow these lichens to exist under the special conditions of a fog desert. We have extended this work by monitoring lichen CO₂ exchange and water relations in spring and by experiments under controlled conditions. In both seasons, nocturnal hydration, by fog and/or dew, activated dark respiration of the lichens which was followed, after sunrise, by a short period of positive net photosynthesis (NP) that continued until metabolic inactivation occurred from desiccation. Dry thalli of T. capensis were able to reactivate NP through water vapour uptake alone, beginning at an air relative humidity of 82%, i.e. at a water potential of −26.3 MPa; the moisture compensation point during desiccation was at 13% thallus water content (WC, dry weight related). Optimal WC for photosynthesis was around 100%, and both species showed a large and extended suprasaturation depression of CO₂ assimilation. Light response showed “sun-plant” characteristics with saturation >1000 μmol m⁻²s⁻¹ photosynthetically active photon flux density (PPFD). However, due to rapid desiccation, the combination of light saturation with optimal WC very rarely occurred under field conditions. Light compensation point after sunrise was highly dependent on actual WC: at low hydration, it amounted to only ca. 10 μmol m⁻² s⁻¹ PPFD so that even the smallest levels of hydration could be used for carbon gain before desiccation took place again. This phenomenon was probably due to a hydration gradient in the thallus branches during transient moistening so that the outer photobiont layer was favoured in contrast to the internal mycobiont which remained dry longer and did not contribute respiratory CO₂ loss. Fully hydrated thalli had light compensation points around 50 μmol m⁻² s⁻¹ PPFD. Extended desiccation of 1–3 days had no impact on the magnitude and recovery of photosynthesis but, imposed desiccation of 10 days reduced NP in lab and field experiments and caused an extended period of recovery. “Resaturation respiration” was not detected in the field data, although it was present after experimental moistening of dry thalli. In spring, the higher fog frequency and intensity increased maximal nocturnal WC, maximal attained NP as well as integrated daily carbon income (ΣNP) compared to the autumn measurements. NPmax and ΣNP depended on maximal nocturnal WC with a saturation-type response. In terms of carbon gain both species seem to be optimally adapted to nocturnal moistening up to 160% WC and were not able to make use of higher degrees of hydration, a feature that might well influence their habitat selection. Maximal daily carbon-related ΣNP for T. capensis was 4.6 mgC (gC)⁻¹ day⁻¹. A rough estimate of the annual (projected) area-related carbon balance (photosynthetic income minus respiratory losses) based on published fog and dew frequencies and personal observations was 15–34 mgC m⁻² yr⁻¹.

    View record details
  • Exact and quasiexact solvability of second-order superintegrable quantum systems: I. Euclidean space preliminaries

    Kalnins, Ernie G.; Miller, W., Jr.; Pogosyan, G.S. (2006-03)

    Journal article
    University of Waikato

    We show that second-order superintegrable systems in two-dimensional and three-dimensional Euclidean space generate both exactly solvable (ES) and quasiexactly solvable (QES) problems in quantum mechanics via separation of variables, and demonstrate the increased insight into the structure of such problems provided by superintegrability. A principal advantage of our analysis using nondegenerate superintegrable systems is that they are multiseparable. Most past separation of variables treatments of QES problems via partial differential equations have only incorporated separability, not multiseparability. Also, we propose another definition of ES and QES. The quantum mechanical problem is called ES if the solution of Schrödinger equation can be expressed in terms of hypergeometric functions mFn and is QES if the Schrödinger equation admits polynomial solutions with coefficients necessarily satisfying a three-term or higher order of recurrence relations. In three dimensions we give an example of a system that is QES in one set of separable coordinates, but is not ES in any other separable coordinates. This example encompasses Ushveridze's tenth-order polynomial QES problem in one set of separable coordinates and also leads to a fourth-order polynomial QES problem in another separable coordinate set.

    View record details
  • An analytical framework for joint vs separate decisions by couples in choice experiments: The case of coastal water quality in Tobago

    Beharry-Borg, Nesha; Hensher, David A.; Scarpa, Riccardo (2009)

    Journal article
    University of Waikato

    This paper offers an analytical framework for analyzing joint and separate decisions by couples in the context of choice experiments for nonmarket valuation. It reports results from an attribute-based stated preference study in which members of couples are asked to conduct a choice-experiment first individually and then jointly. The choice context was the selection of which beach to visit while on vacation in Tobago. Available alternatives differed in attributes related to coastal water and beach quality such as level of coastal development and fish abundance. Tests of preference equality are reported and structured so as to identify the intra-couple decision-making patterns under taste heterogeneity with both finite and continuous mixed logit. Results from the latter suggest that women’s preferences are found to be predominant in the joint choice-experiment. Results suggest caution in using individual choice rather than joint couple choice when valuing quality changes impacting on couple activities, such as water and beach quality in Tobago, and call for further research on the topic.

    View record details
  • Sonochemical preparation of single-dispersion metal nanoparticles from metal salts

    Fujimoto, Toshiyuki; Terauchi, Shin-ya; Umehara, Hiroyuki; Kojima, Isao; Henderson, William (2001)

    Journal article
    University of Waikato

    Novel metal nanoparticles of Pd and Pt were prepared by sonochemical reduction of solutions containing H₂PtCl₆ or K₂PdCl₄. The effect of atmospheric gas on the particle size distribution was investigated. Average diameters and standard deviations of the Pd particles prepared under Ar (Pd/Ar) and N2 (Pd/N₂) were found to be 3.6 ± 0.7 nm (Pd/Ar) and 2.0 ± 0.3 nm (Pd/N₂). Smaller and sharper distribution of the particle size was observed for the Pd particles formed under a N₂ atmosphere. In the case of Pt, a smaller and sharper distribution of the particle size was observed for the particles prepared under a Xe atmosphere. These relations can be explained in terms of a hot-spot temperature created by acoustic cavitation.

    View record details
  • Curing kinetics and effects of fibre surface treatment and curing parameters on the interfacial and tensile properties of hemp/epoxy composites

    Islam, Mohammad Saiful; Pickering, Kim L.; Foreman, Nic J. (2009)

    Journal article
    University of Waikato

    The curing kinetics of neat epoxy (NE) and hemp fibre/epoxy composites was studied and assessed using two dynamic models (the Kissinger and Flynn-Wall-Ozawa Models) and an isothermal model (the Autocatalytic Model) which was generally supported by the experimental data obtained from dynamic and isothermal differential scanning calorimetry (DSC) scans. The activation energies for the curing of composites exhibited lower values compared to curing of NE which is believed to be due to higher nucleophilic activity of the amine groups of the curing agent in the presence of fibres. The highest tensile strength, σ was obtained with composites produced with an epoxy to curing agent ratio of 1:1 and the highest Young's modulus, E was obtained with an epoxy to curing agent ratio of 1:1.2. Alkali treated hemp fibre/epoxy (ATFE) composites were found to have higher σ and E values compared to those for untreated hemp fibre/epoxy (UTFE) composites which was consistent with the trend for interfacial shear strength (IFSS) values. Composites σ and E were found to be higher for a processing temperature of 70°C than for 25°C for both UTFE and ATFE composites, but were found to decrease as the curing temperature was increased further to 120°C.

    View record details
  • Economic implications of herbicide resistance and high labour costs for management of annual barnyardgrass (Echinochloa crus-galli) in Philippine rice farming systems

    Beltran, Jesusa C.; Pannell, David J.; Doole, Graeme J. (2010)

    Journal article
    University of Waikato

    Implications of increasing labour costs and the development of herbicide resistance for profitable weed management in Philippine rice farming systems are investigated. The study employs RIMPhil (Resistance and Integrated Management in the Philippines), a bioeconomic simulation model developed to provide a comprehensive assessment of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus-galli) in rice crops. Results indicate that herbicide application will become increasingly economically attractive, relative to manual weeding, as labour cost increases. This is important since urban migration in the Philippines continues to increase the scarcity of rural labour. Results also show that the onset of herbicide resistance results in substantial losses in farm profit. It is worthwhile for farmers to take management actions to prevent or delay the onset of herbicide resistance, provided that these changes are effective and not too costly. The study highlights the complexity of decision making about integrated weed management on rice farms in the Philippines.

    View record details
  • Obsessive-compulsive disorder (OCD): Gendered metaphors, blogs and online forums

    Campbell, Rebecca; Longhurst, Robyn (2013)

    Journal article
    University of Waikato

    In order to understand social recovery from mental illness, it is important to examine the role played by social space, including virtual space. This article examined blogs and online forums for people with obsessive–compulsive disorder (OCD). In particular, it addressed gender differences in the metaphors used by men and women in these virtual spaces. Empirical data illustrated that, in general, women are more likely to frame their experiences of OCD as a journey, whereas men are more likely to frame them as a battle. Use of these different metaphors has potential implications for social recovery.

    View record details
  • Cost-effective strategies to mitigate multiple pollutants in an agricultural catchment in North Central Victoria, Australia

    Doole, Graeme J.; Vigiak, Olga; Pannell, David J.; Roberts, Anna M. (2013)

    Journal article
    University of Waikato

    Strategies to reduce phosphorus and sediment yields are identified for two Australian catchments using a nonlinear optimisation model. This provides novel insight into the cost-effective management of dual pollutants of water courses in Australia. A strong degree of complementarity between the two pollutants is highlighted, given the adsorption of phosphorus to sediment that augments the value of gully and streambank management for mitigation. However, the relationship between the two pollutants is asymmetric. A 30 per cent reduction in phosphorus yield achieves a 75 per cent reduction in sediment yield in one catchment, while a 30 per cent reduction in sediment yield achieves only a 12 per cent reduction in phosphorus yield. Sediment abatement costs are low given the efficiency of gully and streambank management. A 30 per cent phosphorus reduction lowers profit by 3–7 per cent, while a 30 per cent sediment reduction lowers profit by around 1 per cent. Land-use optimisation requires spatial heterogeneity in land-use and gully/streambank management responses. Overall, this research demonstrates the need to determine whether one pollutant is more important than another, while recognising the potential that mitigation practices possess for the reduction of multiple emissions during their evaluation.

    View record details
  • Oxytocin receptor blockade reduces acquisition but not retrieval of taste aversion and blunts responsiveness of amygdala neurons to an aversive stimulus

    Olszewski, Pawel K.; Waas, Joseph R.; Brooks, Lydia L.; Herisson, Florence; Levine, Allen S. (2013)

    Journal article
    University of Waikato

    When gastrointestinal sickness induced by toxin injection is associated with exposure to novel food, the animal acquires a conditioned taste aversion (CTA). Malaise is accompanied by a surge in oxytocin release and in oxytocin neuronal activity; however, it is unclear whether oxytocin is a key facilitator of aversion or merely its marker. Herein we investigated whether blockade of the oxytocin receptor with the blood–brain barrier penetrant oxytocin receptor antagonist L-368,899 is detrimental for the acquisition and/or retrieval of lithium chloride (LiCl)-dependent CTA to a saccharin solution in mice. We also examined whether L-368,899 given prior to LiCl affects neuronal activity defined through c-Fos immunohistochemistry in select brain sites facilitating CTA acquisition. L-368,899 given prior to LiCl caused a 30% increase in saccharin solution intake in a two-bottle test, but when the antagonist was administered before the two-bottle test, it failed to diminish the retrieval of an existing CTA. LiCl administration increased c-Fos expression in the hypothalamic paraventricular and supraoptic nuclei, area postrema, nucleus of the solitary tract and basolateral and central (CNA) nuclei of the amygdala. L-368,899 injected before LiCl reduced the number of c-Fos positive CNA neurons and brought it down to levels similar to those observed in mice treated only with L-368,899. We conclude that oxytocin is one of the key components in acquisition of LiCl-induced CTA and the aversive response can be alleviated by the oxytocin receptor blockade. Oxytocin receptor antagonism blunts responsiveness of CNA to peripherally injected LiCl.

    View record details
  • Effects on welfare measures of alternative means of accounting for preference heterogeneity in recreational demand models

    Hynes, Stephen; Hanley, Nick; Scarpa, Riccardo (2008)

    Journal article
    University of Waikato

    Multiattribute-revealed preference data are used to investigate heterogeneity in a sample of kayakers for a panel of whitewater sites in Ireland. This article focuses on a comparison of preference heterogeneity using a random parameter logit model with correlated tastes and a latent class model, in terms of the implications for welfare measures of environmental quality and site-access changes. Recreationalists' skill levels are found to affect preferences in both approaches. Statistics for the estimated distribution of welfare changes for the average respondent are computed for changes in site attributes, but contrary to previous work, these are found to be of similar magnitude.

    View record details
  • A mosaic of visions, daydreams, and memories: diverse inlays of organizing and communicating from around the globe

    Broadfoot, Kirsten J.; Cockburn, Tom; Cockburn-Wootten, Cheryl; do Carmo Reis, Maria; Gautam, Dhruba K.; Malshe, Anuradha; Munshi, Debashish; Nelson-Marsh, Natalie; Zakari Okwori, Jenkeri; Simpson, Mary; Srinivas, Nidhi (2008)

    Journal article
    University of Waikato

    This collaboratively multiauthored essay presents diverse tales of organizing and communicative practices in our global context. Authors from India, Nepal, Aotearoa New Zealand, Australia, Brazil, the United States, and Nigeria present individual contributions that coalesce around three clear thematic concerns regarding issues of organizing and communicating: (1) silence and voice, (2) the limits and consequences of linguistic and theoretical translations, and (3) the communal considerations of research politics and participation. The essay concludes with communal reflections on how it is that in attempting to engage with diversity we begin to see remarkable similarities not only in expressing a desire to be heard but also in making a commitment to let others be heard, not only in breaking boundaries and building alliances but also in moving towards a collective, inclusive, and participative conceptualization of the myriad shapes of organizing and communicating that exist in the contemporary global context.

    View record details
  • Immobilization of [Pt₂(μ-S)₂(PPh₃)₄] on polymeric supports by sulfide alkylation and phosphine exchange reactions

    Ujam, Oguejiofo Theophilus; Devey, Kyle; Henderson, William; Nicholson, Brian K.; Mucalo, Michael R.; Decker, Corry; Hor, T.S. Andy (2013)

    Journal article
    University of Waikato

    The immobilization of the dinuclear platinum(II) sulfido complex [Pt₂(μ-S)₂ (PPh₃)₄] on solid supports has been investigated. Reaction with haloalkyl functionalized polymers [Merrifield's resin (chloromethylated polystyrene), chloropropyl silica, chloropropyl controlled pore glass, and bromopropyl polysiloxane] gives complexes immobilized through alkylation of one of the sulfide ligands, forming a μ-thiolate ligand acting as an anchor to the polymer support, akin to well-established reactions of [Pt₂(μ-S)₂(PPh₃)₄] with molecular alkylating agents. The model complex [Pt₂(μ-S)(μ-SCH₂SiMe₃)(PPh₃)₄]PF₆ was prepared as the first molecular silicon-containing derivative of [Pt₂(μ-S)₂(PPh₃)₄] and was fully characterized by NMR spectroscopy, electrospray ionization-mass spectrometry, and single-crystal X-ray diffraction. Immobilization of [Pt₂(μ-S)₂(PPh₃)₄] by phosphine exchange reactions was also achieved using commercial polystyrene-grafted triphenylphosphine or a new immobilized phosphine [derived by sequential functionalization of Merrifield's resin with a polyether amine and then Ph₂PCH₂OH].

    View record details
  • An algorithm for compositional nonblocking verification of extended finite-state machines

    Mohajerani, Sahar; Malik, Robi; Fabian, Martin (2014)

    Conference item
    University of Waikato

    This paper describes an approach for compositional nonblocking verification of discrete event systems modelled as extended finite-state machines (EFSM). Previous results about finite-state machines in lock-step synchronisation are generalised and applied to EFSMs communicating via shared variables. This gives rise to an EFSM-based conflict check algorithm that composes EFSMs gradually and partially unfolds variables as needed. At each step, components are simplified using conflict-equivalence preserving abstraction. The algorithm has been implemented in the discrete event systems tool Supremica. The paper presents experimental results for the verification of two scalable manufacturing system models, and shows that the EFSM-based algorithm verifies some large models faster than previously used methods.

    View record details
  • From unlabelled tweets to Twitter-specific opinion words

    Bravo-Marquez, Felipe; Frank, Eibe; Pfahringer, Bernhard (2015)

    Conference item
    University of Waikato

    In this article, we propose a word-level classification model for automatically generating a Twitter-specific opinion lexicon from a corpus of unlabelled tweets. The tweets from the corpus are represented by two vectors: a bag-of-words vector and a semantic vector based on word-clusters. We propose a distributional representation for words by treating them as the centroids of the tweet vectors in which they appear. The lexicon generation is conducted by training a word-level classifier using these centroids to form the instance space and a seed lexicon to label the training instances. Experimental results show that the two types of tweet vectors complement each other in a statistically significant manner and that our generated lexicon produces significant improvements for tweet-level polarity classification.

    View record details
  • Exact and quasiexact solvability of second order superintegrable quantum systems. II. Relation to separation of variables

    Kalnins, Ernie G.; Miller, W., Jr.; Pogosyan, G.S. (2007-02)

    Journal article
    University of Waikato

    We make explicit the intimate relationship between quasiexact solvability, as expounded, for example, by Ushveridze [Quasi-exactly Solvable Models in Quantum Mechanics (IOP, Bristol, 1993)], and the technique of separation of variables as it applies to specific superintegrable quantum Hamiltonians. It is the multiseparability of superintegrable systems that forces the existence of interesting families of polynomial solutions characteristic of quasiexact solvability that enables us to solve these systems in distinct ways and that gives us the basis of a classification theory. This connection is generalized in terms of the understanding of the role of finite solutions of quantum Hamiltonians

    View record details
  • Influence of accelerated ageing on the physico-mechanical properties of alkali-treated industrial hemp fibre reinforced poly(lactic acid) (PLA) composites

    Islam, Mohammad Saiful; Pickering, Kim L.; Foreman, Nic J. (2010)

    Journal article
    University of Waikato

    30 wt% aligned untreated long hemp fibre/PLA (AUL) and aligned alkali treated long hemp fibre/PLA (AAL) composites were produced by film stacking and subjected to accelerated ageing. Accelerated ageing was carried out using UV irradiation and water spray at 50 °C for four different time intervals (250, 500, 750 and 1000 h). After accelerated ageing, tensile strength (TS), flexural strength, Young's modulus (YM), flexural modulus and mode I fracture toughness (KIc) were found to decrease and impact strength (IS) was found to increase for both AUL and AAL composites. AUL composites had greatest overall reduction in mechanical properties than that for AAL composites upon exposure to accelerated ageing environment. FTIR analysis and crystallinity contents of the accelerated aged composites support the results of the deterioration of mechanical properties upon exposure to accelerated ageing environment.

    View record details
  • The lithospheric geodynamics of plate boundary transpression in New Zealand: Initiating and emplacing subduction along the Hikurangi margin, and the tectonic evolution of the Alpine Fault system

    Furlong, Kevin P.; Kamp, Peter J.J. (2009)

    Journal article
    University of Waikato

    In contrast to the normal ‘Wilson cycle’ sequence of subduction leading to continental collision and associated mountain building, the evolution of the New Zealand plate boundary in the Neogene reflects the converse—initially a period of continental convergence that is followed by the emplacement of subduction. Plate reconstructions allow us to place limits on the location and timing of the continental convergence and subduction zones and the migration of the transition between the two plate boundary regimes. Relative plate motions and reconstructions since the Early to Mid-Miocene require significant continental convergence in advance of the emplacement of the southward migrating Hikurangi subduction—a sequence of tectonism seen in the present plate boundary geography of Hikurangi subduction beneath North Island and convergence in the Southern Alps along the Alpine Fault. In contrast to a transition from subduction to continental convergence where the leading edge of the upper plate is relatively thin and deformable, the transition from a continental convergent regime, with its associated crustal and lithospheric thickening, to subduction of oceanic lithosphere requires substantial thinning (removal) of upper plate continental lithosphere to make room for the slab. The simple structure of the Wadati–Benioff zone seen in the present-day geometry of the subducting Pacific plate beneath North Island indicates that this lithospheric adjustment occurs quickly. Associated with this rapid lithospheric thinning is the development of a series of ephemeral basins, younging to the south, that straddle the migrating slab edge. Based on this association between localized vertical tectonics and slab emplacement, the tectonic history of these basins records the effects of lithospheric delamination driven by the southward migrating leading edge of the subducting Pacific slab. Although the New Zealand plate boundary is often described as simply two subduction zones linked by the transpressive Alpine Fault, in actuality the present is merely a snapshot view of an ongoing and complex evolution from convergence to subduction.

    View record details
  • Environmental practices in the wine industry: An empirical application of the theory of reasoned action and stakeholder theory in the United States and New Zealand

    Marshall, R. Scott; Akoorie, Michèle E.M.; Hamann, Ralph; Sinha, Paresha N. (2010)

    Journal article
    University of Waikato

    Industry transformation related to environmental stewardship has received significant scholarly attention over the past decade. However, limited theoretical and empirical work examines the motivations for improving environmental performance in an industry in different countries. In this paper, we develop a set of hypotheses, based in the theory of reasoned action and stakeholder theory, regarding drivers of the adoption of environmental practices in the wine industries of New Zealand and the United States. We test our hypotheses using data from survey questionnaires collected in each country. Our findings suggest that subjective norms and internal stakeholder pressures are common drivers of the adoption of environmental practices in these two countries. However, managerial attitudes and external stakeholder pressures are not significant drivers. We also find that managerial attitudes and export dependence are stronger determinants of environmental practice adoption in New Zealand compared to the U.S.

    View record details
  • Relationship between soil δ¹⁵N, C/N and N losses across land uses in New Zealand

    Stevenson, Bryan A.; Parfitt, R.L.; Schipper, Louis A.; Baisden, W. Troy; Mudge, Paul Lawrence (2010)

    Journal article
    University of Waikato

    Several of the major processes that result in N loss from soil (nitrification, ammonia volatilization, and denitrification) discriminate against ¹⁵N and fractionate the stable N isotopes, thus δ¹⁵N of ecosystem components has been suggested as an indicator of ecosystem N leakiness. This concept has been applied more successfully to native systems (primarily forest) than to managed systems where N inputs are greater and N cycling processes have potentially been modified. We analysed 210 New Zealand soils (0–100 mm depth) from different land-use systems (increasing in intensity of land use management from indigenous, to plantation forestry, pasture under drystock, pasture under dairy, and cropping) for δ¹⁵N and measures of N availability (total N, C/N, and N mineralization) to determine whether increasing intensity of land use management would lead to increased soil δ¹⁵N values. Mean soil δ¹⁵N differed between land uses with intensively managed cropping having the highest mean soil δ¹⁵N (6.2‰) followed by dairy (5.4‰), drystock (3.8‰), forestry (2.8‰) and indigenous forests (2.1‰). Over all land uses there was a negative correlation between δ¹⁵N and the soil C/N ratio (ρ = −0.73) and regression analysis indicated a relatively strong linear relationship between δ¹⁵N and C/N (r² = 0.56, P < 0.001) when cropping sites (where significant loss of soil C had occurred), and sites with C/N ratio >18 were excluded. Typical N balances for each land use showed that total N loss (and in particular fractionating N losses from ammonia volatilization and nitrate leaching) also increased with increasing land-use intensity. Our results indicate that soil δ¹⁵N may be a useful tool in assessing potential N losses in different soils.

    View record details