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    Productivity, decomposition and carbon sequestration of Chionochloa species across altitudinal gradients in montane tussock grasslands of New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatū, New Zealand
    (Massey University, 2015) Krna, Matthew Aaron
    Anthropogenic activities are drastically altering Earth’s terrestrial, aquatic and atmospheric processes and altering carbon (C) and nutrient cycling. Carbon sequestration, which can be negative feedback to climate change, may help mitigate humanity's impacts on Earth’s climate. Carbon sequestration is a natural process occuring when the fixation of C is greater than the release of C back to the atmosphere from a specified system over an annual timeframe, minimally. Investigation of annual plant productivity, decomposition and alterations in relationships between productivity and decomposition across altitudinal and climate gradients will provide insight into C sequestration driven by environmental and plastic responses of species to climate change. This research investigates how alterations in climate influence ecoclinal populations of Chionochloa species’ in terms of their productivity, decomposition, as well as C and nutrients, across altitudinal gradients on Mounts Tongariro and Mangaweka, Central North Island, New Zealand. Further, impacts on the C sequestration are investigated through alterations in productivity to decomposition ratios (P:D). Reciprocal translocations of living Chionochloa plants and litter decomposition bags were performed across plots every 100m in elevation (equivalent to 0.6oC mean annual lapse rate). Trends were analysed based on experimental plots of origin and destination, and were compared with in situ plants and home site transplants. Productivity of downslope transplants increased at lower elevation plots (i.e. in warmer climates). Leaf litter experienced greater mass loss based on litter translocation to higher elevations on Mount Tongariro and at lower elevations on Mount Mangaweka likely owing to precipitation and temperature gradients respectively. The chemical and constituent composition of leaves and decomposed litter following translocation indicates strong environmental effects on both the plastic responses of plants in growth and the alterations in mass loss from decomposition. Despite chemical and constituent differences in Chionochloa species’ tissues and decomposed litter across gradients, the P:D ratios were greater in warmer environments of lower altitudinal plots. The increased productivity observed outweighs the less-climatically responsive decomposition, indicating greater C sequestration in New Zealand’s tussock grasslands is likely to occur with warming associated with climate change, providing an environmental and economic imperative for conservation of these indigenous grassland systems.
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    Response to water deficit stress in the native New Zealand tussock, Festuca novae-zealandiae : submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy, Department of Plant Biology and Biotechnology, Massey University, Palmerston North, New Zealand
    (Massey University, 1996) Abernethy, Grant Andrew
    Responses to water-deficit stress by a xerophytic tussock native to sub-alpine grasslands of New Zealand have been investigated. Festuca novae-zealandiae possesses some structural adaptions such as curled laminae, limited stomatal distribution, and dense trichomes characteristic of dry-land adapted species. These features were compared with those of a mesophyte, F. arundinacea. In addition to structural adaptions, evidence that metabolic changes contribute to the drought tolerance of F. novae-zealandiae was sought. Plants of F. arundinacea and F. novae-zealandiae were grown in glasshouse pots and were subjected to water-deficit. Concentrations of the phytohormone ABA and the osmoprotectants proline and glycine-betaine increased in mature laminae of F. arundinacea as SWC declined to 8%. In F. novac-zealandiae, ABA concentration increased from 25-50 ng/gDW in two steps. At the first step (at 9-10% SWC), the increase was greatest in leaf bases (to 150 ng/gDW), and the second increase (at 6% SWC) was greatest in laminae (to 320 ng/gDW) and non-existent in leaf bases. In water-sufficient tillers, proline concentration was elevated in leaf bases (5-8 mg/ g DW) compared to laminae (2 mg/ g DW) and increased to 28 mg/ g DW in leaf bases, and to 14 mg/ g DW in laminae as SWC declined to 8-9%. Glycine-betaine concentration (40-100 µmol/ gDW) was unchanged by water-deficit stress. Leaf and tiller counts, and estimates of leaf tip scorching indicated that leaf death progressed with increasing water-deficit. Although leaf elongation declined, it did not cease until the last tillers had died. SDS-PAGE and Western analysis of soluble proteins using antisera to ubiquitin indicated that protein turnover increased in lamina, but not in leaf bases in response to water-deficit. It was concluded that in response to water-deficit stress, leaf bases of F. novae-zealandiae retained turgor and remained viable at the expense of existing leaf laminae, which died back. Southern analysis suggested that the F. novae-zealandiae genome contains sequence(s) with homology to group 2 LEA proteins. Western analysis using antisera raised against the dehydrin consensus sequence KIKEKLPG revealed several related proteins in seeds of F. novae-zealandiae, but these were not induced by water-deficit stress in leaves.