title: Annual carbon balance of an intensively grazed pasture: magnitude and controls

authors: Mudge, Paul Lawrence

subjects: Eddy covariance

abstract: Soil carbon (C) is important because even small changes in soil C can affect atmospheric concentrations of CO₂, which in turn can influence global climate. Adequate soil carbon is also required to maintain soil quality, which is important to if agricultural production is to be sustained. The soil carbon balance of New Zealand's pastoral soils is poorly understood, with recent research showing that soils under dairy pasture have lost large amounts of C during the past few decades. The main objective of this research was to determine an annual farm scale C budget for an intensively grazed dairy farm, with a second objective being to determine the amount of CO₂-C lost following cultivation for pasture renewal, and soil pugging by dairy cattle. A third objective was to investigate the environmental controls of CO₂ exchange in a dairy farm pasture system. Net ecosystem exchange (NEE) of CO₂ was measured using an eddy covariance (EC) system from 15 December 2007 to 14 December 2008. Closed chamber techniques were used to measure CO₂ emissions from three cultivated paddocks and three adjacent pasture paddocks between 26 January 2008 and 5 March 2008. CO₂ emissions were also measured using chambers from pugged and control plots between 25 June and 5 August. Coincidentally this research was carried out in a year with a severe summer/autumn drought and a wetter than usual winter. Annual NEE measured with the eddy covariance system was -1,843 kg C ha⁻¹ (a C gain by the land surface). Accounting for C in supplement import, milk export, pasture export and losses in methane, the dairy pasture system was a net sink of -880±500 kg C ha⁻¹. This C sequestration occurred despite severe drought during the study, which was in contrast to other studies of grasslands during drought. Cultivation under dry conditions did not increase cumulative CO₂-C emissions compared to adjacent pasture paddocks. However, when C inputs to pasture paddocks via photosynthesis were included in calculations, net C loss from the cultivated paddocks (during the 39 day study) was estimated to be 622 kg C ha⁻¹ more than the pasture paddocks. CO₂ emissions were lower from pugged plots compared to control plots, probably caused by decreased microbial and root respiration due to wetter soil conditions, and lowered root respiration as a result of lower pasture production. Volumetric soil moisture content (soil moisture) had a dominant effect on CO₂ exchange at a range of temporal scales. Respiration and photosynthesis were both reduced when soil moisture was below 43% (~the lower limit of readily available water) and photosynthesis virtually ceased when soil moisture declined below 24% (~wilting point). Soil moisture also influenced the relationship between temperature and respiration and photosynthetic flux density (PPFD) and NEE. These results suggest that management related soil disturbances of occasional cultivation for pasture renewal and soil pugging, are unlikely to cause large losses of soil C. Further, a severe drought also did not cause CO₂-C losses from the land surface to the atmosphere on an annual scale, in contrast to previous studies.

text: Annual carbon balance of an intensively grazed pasture: magnitude and controls Soil carbon (C) is important because even small changes in soil C can affect atmospheric concentrations of CO₂, which in turn can influence global climate. Adequate soil carbon is also required to maintain soil quality, which is important to if agricultural production is to be sustained. The soil carbon balance of New Zealand's pastoral soils is poorly understood, with recent research showing that soils under dairy pasture have lost large amounts of C during the past few decades. The main objective of this research was to determine an annual farm scale C budget for an intensively grazed dairy farm, with a second objective being to determine the amount of CO₂-C lost following cultivation for pasture renewal, and soil pugging by dairy cattle. A third objective was to investigate the environmental controls of CO₂ exchange in a dairy farm pasture system. Net ecosystem exchange (NEE) of CO₂ was measured using an eddy covariance (EC) system from 15 December 2007 to 14 December 2008. Closed chamber techniques were used to measure CO₂ emissions from three cultivated paddocks and three adjacent pasture paddocks between 26 January 2008 and 5 March 2008. CO₂ emissions were also measured using chambers from pugged and control plots between 25 June and 5 August. Coincidentally this research was carried out in a year with a severe summer/autumn drought and a wetter than usual winter. Annual NEE measured with the eddy covariance system was -1,843 kg C ha⁻¹ (a C gain by the land surface). Accounting for C in supplement import, milk export, pasture export and losses in methane, the dairy pasture system was a net sink of -880±500 kg C ha⁻¹. This C sequestration occurred despite severe drought during the study, which was in contrast to other studies of grasslands during drought. Cultivation under dry conditions did not increase cumulative CO₂-C emissions compared to adjacent pasture paddocks. However, when C inputs to pasture paddocks via photosynthesis were included in calculations, net C loss from the cultivated paddocks (during the 39 day study) was estimated to be 622 kg C ha⁻¹ more than the pasture paddocks. CO₂ emissions were lower from pugged plots compared to control plots, probably caused by decreased microbial and root respiration due to wetter soil conditions, and lowered root respiration as a result of lower pasture production. Volumetric soil moisture content (soil moisture) had a dominant effect on CO₂ exchange at a range of temporal scales. Respiration and photosynthesis were both reduced when soil moisture was below 43% (~the lower limit of readily available water) and photosynthesis virtually ceased when soil moisture declined below 24% (~wilting point). Soil moisture also influenced the relationship between temperature and respiration and photosynthetic flux density (PPFD) and NEE. These results suggest that management related soil disturbances of occasional cultivation for pasture renewal and soil pugging, are unlikely to cause large losses of soil C. Further, a severe drought also did not cause CO₂-C losses from the land surface to the atmosphere on an annual scale, in contrast to previous studies.

year: 2009

title: Characteristics and origin of black breccia and its relation to adjacent facies within the Martha hill deposit, Waihi

authors: Salsano, Gianluca Domenico

subjects: Waihi

abstract: The Coromandel Volcanic Zone [CVZ] was an active continental volcanic arc between 18 – 1.9 Ma that was responsible for bimodal andesitic–dacitic–rhyolitic volcanism. Following the emplacement of these volcanic formations, some became locally hydrothermally altered to generate ≈ 50 low sulphidation Au–Ag deposits within the CVZ (Hauraki Goldfield). The Martha Hill deposit is a rift–low sulphidation adularia–sericite gold deposit situated in the township of Waihi, New Zealand. Notably, the origin of a black breccia appearing in core logs at the Martha Hill deposit was previously unknown. The focus of this study was to identify the origin of the black breccia through analyses of three separate drill cores (pertaining to the black breccia), and to discover its significance in the paleo–geothermal field at Martha. Analytical techniques included core logging, microscopy, x–ray diffraction [XRD], x–ray flourescence for geochemical majors [XRF] and scanning electron microscopy [SEM]. Initial core logging and analyses recognised 10 new facies relating to the black breccia. These recognised facies fell under three separate categories; two facies for the weakly altered, five for the highly altered and three for the breccia facies. One of the weakly altered facies best reflects the andesite country rock of the Waipupu Formation. The other weakly altered facies is a foreign clast inclusion of a breccia deposited during the original emplacement of the andesite lavas. The five highly altered facies are related to the varying degrees and overprinting events of the paleo–hydrothermal fluid. One of the breccia facies related to the original emplacement of andesite lava as an autobreccia, whilst the other breccia facies was the product of hydraulic fracturing in the sub–surface. Based on core logging, petrographical and geochemical analyses, the black breccia was discovered to be related to diatreme formation. Diatreme formation can vary among deposits due to the post–eruptive hydrothermal environment (high versus low sulphidation) and the nature of the mechanism utilised to generate the diatreme (phreatomagmatism or hydrothermal eruption). However, the poorly sorted, matrix supported nature of the black breccia that was observed during core logging is widely associated with volume expansion (a hydrothermal brecciation mechanism responsible for diatreme formation). Diatreme formation is the result of an increase in temperature or depressurisation. Facies that may suggest the presence of a feeder dike responsible for generating volume expansion and phreatomagmatism was not observed during core logging, but may be present at greater depths or in other drill core. A more likely scenario for the formation of black breccia was due to depressurisation and volume expansion in the near surface due to hydrothermal eruptions. Indeed, initial steam bursts may have ejected cover materials at the surface resulting in depressurisation and boiling in the near–surface. Brecciation and fragmentation would have likely continued and propagated further downward until the steam supply rate was insufficient to further brecciate and uplift rock fragments. Carbonate veins (calcite) that were present during core logging indicates that the paleo–geothermal field reset after the formation of the black breccia and associated diatreme. The presence of adularia indicated by XRD analyses within the black breccia matrix, signifies that the paleo–hydrothermal fluid temperatures after the emplacement of black breccia was ≈ 180 – 350°C.

text: Characteristics and origin of black breccia and its relation to adjacent facies within the Martha hill deposit, Waihi The Coromandel Volcanic Zone [CVZ] was an active continental volcanic arc between 18 – 1.9 Ma that was responsible for bimodal andesitic–dacitic–rhyolitic volcanism. Following the emplacement of these volcanic formations, some became locally hydrothermally altered to generate ≈ 50 low sulphidation Au–Ag deposits within the CVZ (Hauraki Goldfield). The Martha Hill deposit is a rift–low sulphidation adularia–sericite gold deposit situated in the township of Waihi, New Zealand. Notably, the origin of a black breccia appearing in core logs at the Martha Hill deposit was previously unknown. The focus of this study was to identify the origin of the black breccia through analyses of three separate drill cores (pertaining to the black breccia), and to discover its significance in the paleo–geothermal field at Martha. Analytical techniques included core logging, microscopy, x–ray diffraction [XRD], x–ray flourescence for geochemical majors [XRF] and scanning electron microscopy [SEM]. Initial core logging and analyses recognised 10 new facies relating to the black breccia. These recognised facies fell under three separate categories; two facies for the weakly altered, five for the highly altered and three for the breccia facies. One of the weakly altered facies best reflects the andesite country rock of the Waipupu Formation. The other weakly altered facies is a foreign clast inclusion of a breccia deposited during the original emplacement of the andesite lavas. The five highly altered facies are related to the varying degrees and overprinting events of the paleo–hydrothermal fluid. One of the breccia facies related to the original emplacement of andesite lava as an autobreccia, whilst the other breccia facies was the product of hydraulic fracturing in the sub–surface. Based on core logging, petrographical and geochemical analyses, the black breccia was discovered to be related to diatreme formation. Diatreme formation can vary among deposits due to the post–eruptive hydrothermal environment (high versus low sulphidation) and the nature of the mechanism utilised to generate the diatreme (phreatomagmatism or hydrothermal eruption). However, the poorly sorted, matrix supported nature of the black breccia that was observed during core logging is widely associated with volume expansion (a hydrothermal brecciation mechanism responsible for diatreme formation). Diatreme formation is the result of an increase in temperature or depressurisation. Facies that may suggest the presence of a feeder dike responsible for generating volume expansion and phreatomagmatism was not observed during core logging, but may be present at greater depths or in other drill core. A more likely scenario for the formation of black breccia was due to depressurisation and volume expansion in the near surface due to hydrothermal eruptions. Indeed, initial steam bursts may have ejected cover materials at the surface resulting in depressurisation and boiling in the near–surface. Brecciation and fragmentation would have likely continued and propagated further downward until the steam supply rate was insufficient to further brecciate and uplift rock fragments. Carbonate veins (calcite) that were present during core logging indicates that the paleo–geothermal field reset after the formation of the black breccia and associated diatreme. The presence of adularia indicated by XRD analyses within the black breccia matrix, signifies that the paleo–hydrothermal fluid temperatures after the emplacement of black breccia was ≈ 180 – 350°C.

year: 2022

title: Cultural justice, ethics and practice: Summary of presentation

authors: Herbert, Averil May Lloyd

subjects: psychology

abstract: The following cases and remarks are based on the author’s employment over six years
in the Department of Social Welfare in Rotorua Specialist Services. The author
discusses definitions that relate to the topic of cultural justice, ethics, and practice and
our awareness and understanding of the issues; and presents three case studies from practitioner experience.

text: Cultural justice, ethics and practice: Summary of presentation The following cases and remarks are based on the author’s employment over six years
in the Department of Social Welfare in Rotorua Specialist Services. The author
discusses definitions that relate to the topic of cultural justice, ethics, and practice and
our awareness and understanding of the issues; and presents three case studies from practitioner experience.

year: 1993