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Canine (Canis familiaris) scent detection of invasive brown bullhead catfish (Ameriurus nebulosus) in lake water samples
Get PDFBrown bullhead catfish (Ameiurus nebulosus) were deliberately introduced to New Zealand from North America in the 1880s and populations have since increased significantly in the Auckland, Waikato, and Bay of Plenty regions. Catfish pose a major threat to New Zealand’s freshwater ecosystems, preying on and competing with native species for food, and decreasing water clarity through bioturbation and nutrient release.
Early detection of the spread of catfish is crucial as it allows for containment and eradication measures to be set up, preventing the establishment of new catfish populations. However, traditional methods such as visual surveying, netting, and electrofishing are time-consuming and resource intensive, resulting in high costs and restricting the number of locations that can be surveyed. In addition, they can be relatively insensitive when the target biomasses are low, such as in newly establishing populations. False negatives can result in a lack of action from governmental agencies, allowing populations to establish and spread undetected.
Domestic dogs (Canis familiaris) have previously been used for conservation management programmes, detecting reptiles, birds, insects, and larger wildlife animals. Although the use of dogs to detect targets in aquatic environments is relatively new, research has indicated domestic dogs have the ability to discriminate between similar aquatic species and previous projects related to catfish scent detection have shown domestic dogs can detect the presence of catfish in dechlorinated water samples at biologically relevant concentrations.
The aim of this research was to determine whether domestic dogs could detect the presence of catfish in lake water samples at a biomass concentration equivalent to 43.5 kg/ha (based on the assumption of a 2 m deep waterbody), a concentration consistent with the estimated populations of catfish in New Zealand lakes. The first stage of the experiment determined whether dogs could detect the presence of catfish in dechlorinated water samples at a biomass concentration of 43.5 kg/ha. Water samples were collected from tanks containing a standard catfish biomass concentration of 15.5 g/L (equivalent to 38,700 kg/ha) and diluted to 311 kg/ha. As the dogs achieved the discrimination criteria, the sample concentration was progressively decreased. All three dogs were able to detect the presence of catfish at a biomass concentration of 43.5 kg/ha. The next stage of the experiment determined whether domestic dogs could detect the presence of catfish in lake water samples. Lake water samples were collected from catfish-absent Lake Rotomā and spiked with catfish aquaria. As the dogs achieved the discrimination criteria, the catfish concentration was progressively diluted. The majority of the dogs in this study successfully detected the presence of catfish at a biomass concentration of 43.5 kg/ha in lake water samples, with one dog successfully detecting catfish at a biomass concentration of 1.55 kg/ha. In New Zealand, it is highly unlikely significant environmental impacts would occur from a catfish biomass of 1.55 kg/ha. However, targeted eradication of a population density this size would be highly advisable and may be feasibly managed depending on available resources, size of the target water body and its connections to other waterways. The findings in this study indicate the potential utility of dogs in the early detection and management of invasive freshwater species. According to the theory of generalisation, the performance of these dogs may be generalised to different lakes and to different biomass equivalent concentrations without specific training on those lakes or concentrations. However, it would be important to test for this generalisation in future research as differences in stimuli can affect generalisation, with less generalisation occurring as stimuli become increasingly dissimilar from the original training stimulus. Therefore, the differences between the conditions in this study and those in an operational scenario will be important in determining whether the obtained performance will generalise to the operational scenario
Taupiri rau kotahi - Taupiri rau manomano
Get PDFKua roa nei te paepae o Taupiri marae e noho mokemoke ana, i te nuinga o te waa kaaore he tangata hei kawe i ngaa tikanga, aa, kua waiho maa te tokoiti e moohio ana me peewhea te whakahaere tika i ngaa tikanga o te marae. I te nuinga o te waa e waimarie ana maatou mehemea ka tae atu ngaa taangata e rua ki te manaaki i te mauri o te paepae moo te roanga ake o te kaupapa, ahakoa tangihanga mai, huritau mai, aha atu raanei.
I ngaa tau kua kaha kitea ahau te toimaha o teeraa o ngaa haepapa ka taka ki runga i te tokoiti. Naa teenaa, ka hua ake te uho o teenei o ngaa kaupapa rangahau, he waihanga i teetehi rautaki whaikoorero e piki ake ai ngaa nama o te hunga kawe i teenei aahuatanga. Ko taa te tuhingaroa nei he waiho i eetehi moohiotanga hei aawhina, hei whakapakari, hei whakamaamaa i ngaa aahuatanga ka tau ki runga i ngaa taangata whaikoorero. Kua waihotia e au eetehi kura hei aarahi, hei aawhina i ngaa whaanau o te marae, heoti, te hunga e piikoko ana ki te kawe i ngaa taonga o too taatou ahurea.
Ko te tino take kua ahu peenei taku rangahau kia moohio pai ngaa whakatupuranga ki eenei maatauranga, heoti, kia moohio pai ngaa whakatupuranga me peewhea te whakahaere i eenei aahuatanga. I runga anoo i te tuupono ka tae mai ki te waa me manaaki te reanga rangatahi i te paepae, ka taka raanei te haepapa whakahaere paepae ki a maatou te hunga rangatahi, ko te wawata ia ka aawhina teenei tuhingaroa i a taatou. Kaaore e kore hei ngaa tau e heke mai nei ka kii pohapoha te paepae o Taupiri marae i te hunga e moohio ana ki te whakatakoto i aana kupu, ki te whaikoorero. Koia te take i hua mai te ingoa o teenei o ngaa tuhingaroa, maa te whaangai i te rau kotahi ko te whaainga ia aa toona waa ka hora katoa eeraa maatauranga ki ngaa rau manomano.
“Hei aha te pae nekeneke, waiho mai raa ki ahau he pae kounga, he pae motuhake
Caffeine Modifies the Immune and Anti-inflammatory Responses to Short Incremental Cycling Exercise Until Exhaustion in Humans: A Pilot Study
Get PDFExercise has well-documented effects on immune function with both positive and negative sequelae dependent on intensity, volume, and duration. The immunosuppressive effects of exercise are mediated, in part, by the complex interaction of cytokines, catecholamines, and nutrition. Caffeine has been reported to modulate immune function; however, the interaction with brief exhaustive exercise is not well characterized. It was hypothesized that caffeine would upregulate the cytokine response to intense exercise. Seven male students volunteered to participate in a randomized, double-blinded crossover study where they ingested either caffeine (6 mg/kg) or a maltodextrin placebo (6 mg/kg) 1 h prior to a cycling exercise. The exercise protocol started at 100 W and the intensity was increased by 50 W every two minutes until exhaustion. Serum samples were collected pre-, post-, and 1-h post-exercise and analyzed for IL-4, IL-10, and TGF-β1. Caffeine ingestion increased time to exhaustion (P = 0.005; Effect Size [ES] = 1.33), IL-4 (P = 0.004; ES = 2.34), IL-10 (P = 0.047; ES = 0.41 ± 0.57), and TGF-β1 (P = 0.013; ES = 0.76). The accentuated response of the cytokines may have important ramifications due to their potent anti-inflammatory and immunoregulatory properties. Specifically, the 6 mg/kg caffeine dose not only improved exercise performance but the cytokine data is indicative of an upregulated inflammatory response and an enhancement of the anti-inflammatory benefits of exercise
Settler colonial bordering and post-pandemic futures: disrupting the nation state in Aotearoa/New Zealand
Get PDFIn Aotearoa / NewZealand, the relative safety offered by border regime closures during Covid-19 promised to ease uncertainty surrounding perilous futures, yet it did so by extending nation building into more intimate areas of life, exacerbating existing lines of discrimination. While justified in terms of crisis management, state expressions of citizen care during the pandemic were largely modelled in terms of a particular conflation of nature, society and economy peculiar to settler colonialism. Using bordering practices during the pandemic as a point of departure, this essay draws on scholarship on borders to interrogate settler colonialism in Aotearoa. This allows for four innovations: First, it situates Covid-19 as structure rather than event, one which accentuated historical patterns of nation-making. Second, it underscores continuities in Indigenous relations of ownership, belonging, social reproduction, kinship ethics and environmental engagements. Third, it suggests alliances between migrants, non-white and colonized peoples; those for whom borders do not remain at the periphery, but rather penetrate deep into the informal spaces of the everyday. And fourth, it recalibrates resistances as expressions of sociality aimed at reclassifying nature, economy and society
Microbial biogeography of 1,000 geothermal springs: spatial, temporal, and allopatric dynamics of extremophiles in the Taupō Volcanic Zone, Aotearoa-New Zealand
Get PDFGeothermal springs are model ecosystems to investigate microbial biogeography as they represent discrete, relatively homogeneous habitats, are distributed across multiple geographical scales, and span broad geochemical gradients. This thesis reports the largest consolidated study of geothermal ecosystems to determine causal factors that influence both spatial and temporal biogeographical patterns of extremophiles. Bacterial and archaeal community composition, 46 physicochemical parameters, and metadata from 925 geothermal spring water columns across the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand were measured. Standardised methodologies were employed to define microbial diversity via 16S rRNA gene amplicon sequencing, and associated physicochemistry, ensuring confidence in sample comparison. Over an 8,000 km² spatial scale, multivariate statistical analyses determined diversity was primarily influenced by pH at temperatures 70 °C. Further, community dissimilarity increased with increasing geographic distance across the region, highlighting niche selection driving assembly at a local scale.
This research also describes the first comprehensive temporal study of geothermal microbial communities in Aotearoa-New Zealand. One hundred and fifteen water column samples from 31 geothermal features were taken over a 34-month period to ascertain microbial community stability, community response to both natural and anthropogenic disturbances in the local environment, and temporal variation in spring diversity across the pH range found in the TVZ. Results indicated temperature and associated groundwater physicochemistry were the most likely parameters to vary stochastically in these geothermal features, with community abundances rather than composition more readily affected by a changing environment. However, variation in pH (pH ±1) had a more significant effect on community structure than temperature (±20 °C), with alpha diversity failing to be an adequate measure of temporal microbial disparity in geothermal features outside of circumneutral conditions. While a substantial physicochemical disturbance was required to shift community structures at the phylum level, geothermal ecosystems were resilient at this broad taxonomic rank and returned to a pre-disturbed state if environmental conditions re-established.
The discovery that genus (phylum Aquificota) exhibited the greatest average abundance (11.2 %) and distribution (74.2 %) of all taxa across 925 geothermal ecosystems in the TVZ, and an apparent absence of this taxon in global geothermal systems, led to the hypothesis that allopatric speciation enabled the evolution of an endemic bacterial genus to Aotearoa-New Zealand. Maximal read abundance of occurred in geothermal features with pH 4-6, 50-70 °C, and low oxidation-reduction potentials, highlighting a specific environmental niche that could enhance habitat isolation. Genomic analysis of the only characterised species for the genus, CP.B2ᵀ, confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between populations illustrated dispersal was not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of local and global microbial communities from DNA sequence databases indicated is geographically restricted to the Aotearoa-New Zealand archipelago. It was concluded that combined geographical and physicochemical constraints prevent this taxon from distributing on a broader scale, resulting in the establishment of an endemic bacterial genus.
Collectively, the findings from this thesis provide an insight into ecological behaviour in geothermal springs, highlighting the diverse controls between different taxa within the same habitat-type, and expand understanding of microbial biogeography in extreme ecosystems
Pinnip pinainthu kidakkum oorangattthalkalai kattudaiththal: Reimagining social activism with intersectional subaltern activist consciousness
Get PDFPeople have been marginalised and oppressed due to their beliefs, identities, and expressions based on race, ethnicity, sex, gender, language, religion, class, caste, disability, neurodiversity, and sexuality for centuries. In Sri Lanka, these are deeply rooted and intertwined with historical violence, colonisation, and generational pain and suffering. Every instance of marginalisation and oppression, especially in the North and the East of this war-torn ‘teardrop island’ in the Indian Ocean, is a product of multiple crimes against humanity at various levels. Alongside marginalisations and oppressions exist the powerful instances, journeys, and stories of resistance, social organising, celebrations, and social movement building based on a profound sense of solidarity. Over the years, they have produced many seedlings of manifestations that keep these powerful instances alive and continually evolving. This doctoral thesis is one such seedling.
Driven by the desire to theorise with subaltern activist journeys, this thesis explores the textures and contours of social activism organised by young trans, intersex and women activists from the margins who seek social justice in post-war Northern Sri Lanka. It searches for voices and experiences pushed to the margins by hegemonic and destructive powers and structures of society. By treating them as credible knowers, the thesis co-weaves a metaphorical mat of activist consciousness to argue i) particular experiences of subalternity emerge in post-war justice movements, ii) activist consciousnesses are shaped by everyday struggles that are constantly changing and evolving as activists navigate precarious living due to multiple and intersecting forms of marginalisation, iii) activists engage in reactive and proactive processes to manifest purposes beyond their differences and challenge forms of marginalisation, address the legacies of differences, and work towards justice and changes, iv) collaborative consciousness promotes collective growth, v) activists produce imaginaries of justice beyond binary thinking and understanding of their social worlds, and vi) critiquing practices aimed at critical reflections on the self as well collectives deepen understanding of the subalternity of social transformations. Conceptual frameworks from particular subaltern locations and histories substantiate these claims. The thesis concludes with suggestions for future researchers to further generate knowledge in collaboration with collective social processes
Exploring patient experiences and power dynamics in an acute general surgical ward: A mixed methods study exploring patient and staff perceptions of the inpatient experience at Waikato Hospital
Get PDFBackground: Alongside health outcomes, patient experiences are considered crucial in identifying the quality of a health care setting. General surgery comprise the largest range of pathologies and accounts for the highest number of patient discharges of any surgical specialty. As a way to address the power imbalance between healthcare staff and patients, patient-centred models of care are increasingly being adopted and implemented within hospitals including surgery. This study aims to investigate the current experiences of acutely admitted patients in a general surgical ward at Waikato Hospital, including opportunities for and challenges to improvement initiatives. Furthermore, the study examines relevant staff members perspectives of the inpatient experience and seeks to determine the efficacy of a proposed intervention focusing on empowering patients and their families.
Methods: The study was a mixed method design involving two phases. Phase I obtained qualitative data from semi-structured interviews with six patients and twelve staff members. Themes which emerged from the qualitative data in phase I were used to inform the development of phase II, as well as to inform a proposed patient self- assessment intervention. Phase II obtained quantitative data through Likert scale response surveys provided to acute patients on, or near to, their day of discharge from the surgical ward over a two month period.
Results: A total of six patients and 12 healthcare staff (senior registered nurses, n=3; surgical registered nurse managers, n=2; surgical fellows, n=2; surgical registrar, n=1; dietitian, n=1; social worker, n=1; occupational therapist, n=1; and physiotherapist n=1) were involved in phase I. A total of 53 surveys were returned from patients in Phase II (63.1% response rate). Qualitative data from phase I was analysed using a general inductive approach. This revealed three themes including power and control concerns for patients, the hierarchy of the health care team and the surrounding stressors of the organisation and environment. Analysis of the quantitative data collected descriptive statistics and calculated chi-squares. Of note were the statistically significant differences particularly between patients of Māori ethnicity comparatively to non-Māori, and according to gender and reason in hospital. There were no statistically significant differences for patients according to age group.
Conclusion: This study identified both the experiences of patients and staff in an acute general surgical context. The study found that the proposed patient self- assessment intervention was not immediately recommended. This was due to the current recommendations from patients who identified their strong preference was for face-to-face communication with staff. It was also due to staff members identification of a perceived inability to consistently provide person-centred care which corresponded with the patient self-assessment data. Acute general surgical care needs of patients were perceived by staff as taking precedent and current workplace stressors, including staffing and skill mix deficits and perceived lack of staff wellbeing supports, were strong inhibitors for staff to provide their preferred capacity of patient-centred care
'Spinning Straw Into Gold': Nacho Video and the Exquisite Corpse of Fan-editing
No full textAn exploration of YouTube as a platform for remix, reuse, and samplin
Why we're seduced by climate tech and what it means for our happiness
Get PDFFor the most climate-anxious among us, it may even seem best to succumb to the climate tech horizon bias because of the short-term happiness benefits. However, recent research and personal experience are increasingly revealing that the climate catastrophe has already begun. Severe weather events, sea-level rise, and record-breaking heatwaves are impacting millions of people around the world, and doing so with increasing frequency (IPCC, 2023). In the face of this overwhelming evidence, nearly everyone (that doesn't already) should realize that climate tech is not a complete solution to the climate crisis. For those so in the grip of the climate tech horizon bias that they haven't done anything to help address climate change, the happiness impacts of being exposed to extreme weather events and other climate-change-related harms (Clayton, 2020) will include the extra sting of realizing that they had been seduced by the easy solace offered by over-hyped climate tech, and that they could have done more to prevent this affront to their and others' happiness.
Human selfishness, weakness of will, and uncritical thinking are the root problems. Climate tech is part of the solution but, thanks to the horizon bias, may exacerbate the climate problem and cause unhappiness if it is relied upon too heavily. Given the current climate crisis, some unhappiness seems unavoidable. In our view, the best solution is to keep acting in climate friendly ways as individuals, which includes joining with others to encourage governments and businesses to take immediate large-scale steps to reduce emissions as well as mitigate the ongoing effects of historical emissions. Schwartz et al. (2022) found that collective climate action seemed the most likely way to prevent climate anxiety turning into depression, plausibly because it alleviates feelings of individual powerlessness. Perhaps even more importantly, collective climate action may be necessary to prevent a future marred with many climate catastrophes (Gonzalez-Perez and Piedrahita-Carvajal, 2022) and the widespread unhappiness they would cause. So while we should empower promising climate tech by investing in it, we should also empower ourselves by joining with others and pushing for immediate emissions reductions. If we're right, this will make us happier individually and collectively, especially in the medium- and long-run
A study of some aspects of the nitrogen economy of New Zealand grassland soils
No full textNitrogen deficiency is widespread and is a major limitation to grassland productivity in New Zealand, indicating inadequate nitrogen supply, losses from the nitrogen cycle, or a combination of both. The intensive grassland farming system on which New Zealand agriculture is based is largely dependent on symbiotic fixation of atmospheric nitrogen by clovers, and many estimates indicate that the amount of nitrogen fixed annually should be adequate to maintain a high level of pasture production. It appears, therefore, that losses of nitrogen be the more important factor contributing to nitrogen deficiency in New Zealand pastures. One transformation which will affect the conservation of nitrogen in soil, and which has received little attention in New Zealand, is nitrification. It was the objective of this thesis to investigate some aspects of nitrification in New Zealand grassland soils.
A technique which has recently been applied to studies on nitrogen transformations in soils involves the use of variations in the natural abundance of ¹⁵N. The possible use of this technique for studying nitrogen transformations in New Zealand soils was investigated.
A perfusion technique suitable for the measurement of inherent oxidation activities of the indigenous nitrifying organisms in New Zealand grassland soils was developed. Soils were perfused with 0.005M (NH₄)₂SO₄ at 25°C, and the rate of oxidation of ammonium to nitrate measured over a sixteen hour period. Rates of nitrification measured over the initial sixteen hours of perfusion, referred to as the Initial Nitrification Activity (INA), ranged from <0.02 μg Noxidised/g soil/hour to 5.70 μg Noxidised/g soil/hour in sixty nine soils selected to provide a representative sample of agricultural soils from the major soil groups of New Zealand.
High rates of INA (>2 μg N oxidised/g soil/hour) were found in yellow-brown loams, some red and brown loams, and soils with a pH above 7.0. All other soils exhibited rates of nitrification <1 μg Noxidised/g soil/hour.
Differences in INA were found to predict the rates of nitrification occurring in the field in two soils using an in-situ incubation technique. The mean rate of nett nitrification measured over a forty seven week period in the 0 - 7.5 cm depth of Wharekohe silt loam (INA= 0.07 μg Noxidised/g soil/hour), was 0.68 x 10⁻² μg Noxidised/g soil/hour, and that in the 0 - 7. 5 cm depth of Kiripaka silt loam (INA = 0.81 μg Noxidised/g soil/hour) was 5.4 x 10⁻² μg Noxidised/g soil/hour. This difference resulted in a different ratio of ammonium to nitrate between the soils. In Wharekohe, the mean values of ammonium and nitrate nitrogen present in the 0 - 7.5 cm depth over the forty seven week experimental period were 15.7 ± 1.7 and 0.9 ± 0.4 kg N/ha respectively. In Kiripaka, the figures were 6.5 ± 1.3 and 6.6 ± 1.4 kg N/ha.
Rates of nett mineralisation of soil organic nitrogen were also determined in Wharekohe silt loam and Kiripaka silt loam by an in-situ incubation technique. In the former soil, the mean rate of nett mineralisation over a forty seven week period was 0.99 ± 0.08 kg N/ha (0 - 7.5 cm)/day, and in the latter soil 0.74 kg N/ha (0 - 7.5 cm)/day.
When soils were perfused with 0.005M (NH₄)₂SO₄ for up to twenty days, four general patterns of nitrification were observed.
1) Ammonium was rapidly oxidised to nitrate, the rate of oxidation being linear or near linear from the commencement of the perfusion.
2) Ammonium was oxidised only slowly to nitrate.
3) Ammonium was oxidised slowly to nitrate at the commencement of perfusion, but increased logarithmically with time until a steady rate of nitrification was observed.
4) Type 3 nitrification with a temporary accumulation of nitrite during the initial stages of perfusion.
Type 1 nitrification was observed only in soils having a high INA, type 2 nitrification in soils of low pH (mean pH 5.5), and type 4 nitrification only in soils with a pH above 7.0, with the exception of two podzolic soils. Type 3 nitrification was observed in the majority of the soils studied.
Large populations of ammonium oxidisers (1.6- x 10⁴ to 2.2 x 10⁶/g soil) and nitrite oxidisers (5.4 x 10⁴ to 1.9 x 10⁷/g soil) were found in the 0 - 7. 5 cm depth in New Zealand soils under improved grassland. In contrast to these high numbers, a low population of nitrifying organisms (555 ammonium oxidisers and 1434 nitrite oxidisers/g soil) was found in a native forest soil. Populations of nitrifying organisms were largest close to the soil surface and, in general, declined with depth.
Generation times of ammonium oxidisers were estimated to be in the order of three to five days and were dependent on pH. A variation in the rate of ammonium oxidation per ammonium oxidising cell was found between soils, therefore INA could not be considered as indicative of the size of the nitrifying population.
Multiple linear regression analysis showed both pH and percent total nitrogen to be significantly correlated with INA. A detailed study of the effect of pH on nitrification showed that soils containing allophane, an amorphous aluminium silicate, exhibited higher rates of nitrification at a given pH than other soils. Nitrification was also able to proceed at lower pH values in the former soils than in the latter. This difference may be partly rationalised by theoretical differences in surface pH of soil colloids.
A study was made of the fate of ¹⁵N enriched Ca(NO₃)₂ and (NH₄)₂SO₄ applied to two soils, one of medium (Waimate North clay loam) and the other of low (Wharekohe silt loam) INA. Recovery of Ca(NO₃)₂ and (NH₄)₂SO₄ nitrogen in pasture herbage was 47.4 and 35.8 percent on the former soil, and 20.3 and 42.5 percent on the latter respectively. After soil nitrogen was taken into account there was still up to 66.8 percent of the nitrogen applied not accounted for. It was concluded that leaching was the major mechanism of loss, although some evidence of losses by denitrification from the Wharekohe soil was found.
The differences in rates of nitrification measured in New Zealand grassland soils are of agronomic significance since the rate of nitrification determines the form of inorganic nitrogen available for plant uptake. Ammonium, and not nitrate, is the major form of nitrogen available for assimilation by plants in several yellow-brown earths, and also in some podzolic soils, yellow-brown sands, recent soils from alluvium and yellow-brown pumice soils. Although differences in rates of nitrification do not appear to affect pasture production, they will, of necessity have to be considered if specialised crops which show a preference for assimilation of either ammonium or nitrate ate grown on these soils.
Soils having a high rate of nitrification are associated with high concentrations of nitrate in groundwaters of the Waikato.
A low rate of nitrification in soils such as Wharekohe silt loam appears to be an important mechanism for the conservation of nitrogen. Any agricultural practice which will increase the rate of nitrification should be carefully considered and the overall effect on the nitrogen economy of the soil evaluated. If increasing the rate of nitrification results in a lower nitrogen status, then increased inputs of nitrogen either by symbiotic nitrogen fixation or fertiliser application will be required to maintain the same level of pasture production.
In general, it appears that the disadvantages of high rates of nitrification outweigh the advantages, and agricultural practices should therefore be designed to minimise the rate of nitrification in soils.
The extent of nitrogen isotope discrimination in various reactions occurring in New Zealand soil-pasture systems was determined. Symbiotic fixation of atmospheric nitrogen by clover, assimilation of inorganic nitrogen by Trifolium repens, the oxidation of ammonium to nitrate by nitrifying organisms and the volatilisation of NH₃ from urine spots all showed discrimination in favour of ¹⁴N. A previously unmeasured fractionation in animals was determined. In cattle, urine was depleted by about 2%₀ and faeces enriched by about 2%₀ relative to the animal feed.
δ¹⁵N values were measured in the 0 - 7.5 cm depth of sixty one New Zealand grassland soils. The mean δ¹⁵N value was 3.2%₀ with a range of -1.1 to 6.8%₀. The δ¹⁵N values in two soil profiles showed that δ¹⁵N values increased with depth reaching a maximum value at 20 cm in Wharekohe silt loam and 50 cm in Waimate North clay loam. New Zealand soils appear to be less enriched in ¹⁵N than many American soils, and it is suggested that this reflects the large annual input of symbiotically fixed nitrogen which has a negative δ¹⁵N value, although the mechanism of loss (i.e. via denitrification, leaching or volatilisation of NH₃) of nitrogen from different soils may be important.
δ¹⁵N values were also determined for nitrate nitrogen in ground water collected from a limestone cave under native forest in the Waitomo region, and also for nitrate nitrogen in the groundwater of shallow aquifiers in the Waikato.
The δ¹⁵N values for two groundwater samples from the Waitomo area were - 1.6 and 3.8%₀ while nine samples collected from the Waikato were in the range of 5.2 to 10.0%₀. It is suggested that the isotopic composition of groundwater nitrogen in the Waikato is a result of a major contribution of nitrogen derived from urine. This suggests that the grazing animal is an important contributor to the high nitrate concentration in groundwaters of the Waikato.
Because of the variability of δ¹⁵N values that were found in grazed soil-pasture systems, and the complexity of fractionations which occur in such systems, small variations in the natural abundance of ¹⁵N appear to be only of limited use for even qualitative studies of nitrogen transformations