title: Dissolution and depletion of ferromagnesian minerals from Holocene tephra layers in an acid bog, New Zealand, and implications for tephra correlation

authors: Hodder, A.P.W.

subjects: chemical weathering

abstract: This study examines the depletion of ferromagnesian silicate minerals from a sequence of thin, distal, mainly rhyolitic tephra layers of Holocene age preserved in an acid peat bog (Kopouatai), North Island, New Zealand. The rate of such depletion has been fast, as indicated by the complete loss of biotite from one tephra layer (Kaharoa Tephra), in which it is normally dominant, in only ca. 770 yr. Chemical dissolution is advocated as the likely cause for the depletion, with amphiboles and other mineral grains commonly showing etch pits, microcaves, and other characteristic surface solution features. Theoretical thermodynamic and kinetic models show a marked increase in the rate of dissolution of all ferromagnesian minerals under conditions of low pH (< 4), but that where silica concentrations in solution are high the relative proportions of minerals remaining are unaffected. However, where concentrations of dissolved silica are low, as in most bog environments, the relative proportions of ferromagnesian minerals are affected as well as absolute amounts being decreased. Amphiboles are depleted relative to pyroxenes, consistent with kinetic studies.
The results show that the identification and correlation of tephras on the basis of relative abundances of ferromagnesian minerals alone may be unreliable, and emphasise the need to use multiple criteria in such studies.

text: Dissolution and depletion of ferromagnesian minerals from Holocene tephra layers in an acid bog, New Zealand, and implications for tephra correlation This study examines the depletion of ferromagnesian silicate minerals from a sequence of thin, distal, mainly rhyolitic tephra layers of Holocene age preserved in an acid peat bog (Kopouatai), North Island, New Zealand. The rate of such depletion has been fast, as indicated by the complete loss of biotite from one tephra layer (Kaharoa Tephra), in which it is normally dominant, in only ca. 770 yr. Chemical dissolution is advocated as the likely cause for the depletion, with amphiboles and other mineral grains commonly showing etch pits, microcaves, and other characteristic surface solution features. Theoretical thermodynamic and kinetic models show a marked increase in the rate of dissolution of all ferromagnesian minerals under conditions of low pH (< 4), but that where silica concentrations in solution are high the relative proportions of minerals remaining are unaffected. However, where concentrations of dissolved silica are low, as in most bog environments, the relative proportions of ferromagnesian minerals are affected as well as absolute amounts being decreased. Amphiboles are depleted relative to pyroxenes, consistent with kinetic studies.
The results show that the identification and correlation of tephras on the basis of relative abundances of ferromagnesian minerals alone may be unreliable, and emphasise the need to use multiple criteria in such studies.

year: 1991

title: Leaf-level coordination principles propagate to the ecosystem scale.

authors: Gomarasca, Ulisse

subjects: Ecosystem

abstract: Fundamental axes of variation in plant traits result from trade-offs between costs and benefits of resource-use strategies at the leaf scale. However, it is unclear whether similar trade-offs propagate to the ecosystem level. Here, we test whether trait correlation patterns predicted by three well-known leaf- and plant-level coordination theories - the leaf economics spectrum, the global spectrum of plant form and function, and the least-cost hypothesis - are also observed between community mean traits and ecosystem processes. We combined ecosystem functional properties from FLUXNET sites, vegetation properties, and community mean plant traits into three corresponding principal component analyses. We find that the leaf economics spectrum (90 sites), the global spectrum of plant form and function (89 sites), and the least-cost hypothesis (82 sites) all propagate at the ecosystem level. However, we also find evidence of additional scale-emergent properties. Evaluating the coordination of ecosystem functional properties may aid the development of more realistic global dynamic vegetation models with critical empirical data, reducing the uncertainty of climate change projections.

text: Leaf-level coordination principles propagate to the ecosystem scale. Fundamental axes of variation in plant traits result from trade-offs between costs and benefits of resource-use strategies at the leaf scale. However, it is unclear whether similar trade-offs propagate to the ecosystem level. Here, we test whether trait correlation patterns predicted by three well-known leaf- and plant-level coordination theories - the leaf economics spectrum, the global spectrum of plant form and function, and the least-cost hypothesis - are also observed between community mean traits and ecosystem processes. We combined ecosystem functional properties from FLUXNET sites, vegetation properties, and community mean plant traits into three corresponding principal component analyses. We find that the leaf economics spectrum (90 sites), the global spectrum of plant form and function (89 sites), and the least-cost hypothesis (82 sites) all propagate at the ecosystem level. However, we also find evidence of additional scale-emergent properties. Evaluating the coordination of ecosystem functional properties may aid the development of more realistic global dynamic vegetation models with critical empirical data, reducing the uncertainty of climate change projections.

year: 2023-07-04

title: Reclaiming Kaitiakitanga : An intergenerational perspective of Kaitiakitanga within Te Parawhau

authors: Walker, Erana

subjects: Kaitiakitanga

abstract: Kaitiakitanga is a concept that is utilised widely throughout the Māori world for the protection and preservation of cultural aspects to Māori. Through years of application by westernised mainstream processes the value has largely been restricted to the realms of environmental protection. This restriction has often been the result of misinterpretation of Kaitiakitanga and its relevance as a concept to Māori. The purpose of the thesis is to question how the perspective of Kaitiakitanga is constructed in the minds of representatives from the hapū of Te Parawhau. To test for variance, the research spans across two generations of hapū members. Using Whakawhiti Kōrero for data collection as well as Kaupapa Māori methodology as guidance, the thesis explores perspectives of two generations of Te Parawhau descendants around Kaitiakitanga and how it can be developed to aid in the growth and prosperity of the hapū. Key themes highlighted by the analysis encompass ideas of connectedness as well as spiritual, physical, environmental and human elements of responsibility and obligation. The thesis introduces a distinct Te Parawhau analytical framework for its analysis of rich kōrero by hapū members in relation to Kaitiakitanga. Through this framework the value of Kaitiakitanga is tested for relevance to Te Parawhau and its future development. The world view of Te Parawhau has formed the basis of participant perspectives around Kaitiakitanga and leads the researcher to consider that such knowledge is important to the future functionality of Māori value’s. The thesis concludes to show that there are indeed differences in application and perspectives of Kaitiakitanga within the hapū of Te Parawhau.

text: Reclaiming Kaitiakitanga : An intergenerational perspective of Kaitiakitanga within Te Parawhau Kaitiakitanga is a concept that is utilised widely throughout the Māori world for the protection and preservation of cultural aspects to Māori. Through years of application by westernised mainstream processes the value has largely been restricted to the realms of environmental protection. This restriction has often been the result of misinterpretation of Kaitiakitanga and its relevance as a concept to Māori. The purpose of the thesis is to question how the perspective of Kaitiakitanga is constructed in the minds of representatives from the hapū of Te Parawhau. To test for variance, the research spans across two generations of hapū members. Using Whakawhiti Kōrero for data collection as well as Kaupapa Māori methodology as guidance, the thesis explores perspectives of two generations of Te Parawhau descendants around Kaitiakitanga and how it can be developed to aid in the growth and prosperity of the hapū. Key themes highlighted by the analysis encompass ideas of connectedness as well as spiritual, physical, environmental and human elements of responsibility and obligation. The thesis introduces a distinct Te Parawhau analytical framework for its analysis of rich kōrero by hapū members in relation to Kaitiakitanga. Through this framework the value of Kaitiakitanga is tested for relevance to Te Parawhau and its future development. The world view of Te Parawhau has formed the basis of participant perspectives around Kaitiakitanga and leads the researcher to consider that such knowledge is important to the future functionality of Māori value’s. The thesis concludes to show that there are indeed differences in application and perspectives of Kaitiakitanga within the hapū of Te Parawhau.

year: 2016