title: Restiad bog development and nutrient dynamics of the dominant species

authors: Clarkson, Beverley R.

subjects: bog succession

abstract: Vegetation and peat in lowland restiad (dominated by Restionaceae) raised bogs on North Island (Waikato region) and Chatham Island, New Zealand, were sampled to investigate the main environmental controls of pattern and change. Vegetation classification based on a chronosequence of Waikato restiad bogs revealed a sequence from sedges, through Empodisma minus, the main peatforming restiad, to phases dominated by a second restiad, Sporadanthus ferrugineus. The sequence paralleled temporal successional patterns and was used for interpreting plant-nutrient dynamics along a successional gradient. As succession proceeds, von Post (an index of peat decomposition), total P, total N and % ash in peat decrease. Empodisma was considered to be the key species in restiad bog development. It is tolerant of a wide environmental range, establishing early in minerotrophic wetlands to initiate restiad bog development, and persisting through to late ombrotrophic phases. On Chatham Island, the ecological role of Sporadanthus traversii in restiad bog development is similar to Empodisma in Waikato, being the main peat former and occupying a wide environmental range. Peat under S. traversii had significantly higher total N, total K, available P, bulk density and von Post, and lower pH than Waikato peats under S. ferrugineus or Empodisma. This was attributed to a strong oceanic influence and long history of sea-bird nutrient inputs. 
Nutrient responses in the heath and restiad components of the bog were compared by measuring plant ¹⁵N natural abundance across N and P gradients. Heath shrubs revealed considerable isotopic variation (-2.03 to - 15.55 for Leptospermum scoparium), with foliar δ¹⁵N strongly positively correlated with P concentrations in foliage and peat. In contrast, restiad species revealed little isotopic variation, with Empodisma and S. traversii having δ¹⁵N levels around 0‰, and S. ferrugineus being significantly more depleted (mean -4.97‰). The differences in ii isotopic signatures between heath shrubs and restiads were linked to contrasting nutrient demands, acquisition mechanisms, and root morphology. Leptospermum shrubs on low nutrient peats were stunted, with low foliar %P and high N:P ratios, suggesting they were P-limited. The concurrence of δ¹⁵N depletion and %P in plant tissues suggests N fractionation is promoted by P limitation. In contrast, the constancy in δ¹⁵N of the restiad species through the nutrient gradients indicates these may not be P-limited. 
The contrasting δ¹⁵N signatures of co-habiting Empodisma and S. ferrugineus in late successional bogs suggest the species are accessing different sources of N. Empodisma has a thick layer of cluster roots overlying the deeper S. ferrugineus roots, and would be better positioned to intercept aerially derived N. The hypothesis that this root disposition allows Empodisma to preferentially access the primary N input from rainfall was tested using a ¹⁵N-enriched tracer. At plots codominated by Empodisma and S.ferrugineus, 1.6 mmoles m-2 of 99 atom% excess ¹⁵N as (NH4)2S04 was applied to the peat surface, followed by deionised water, simulating a rainfall event of 34 mm. After 5 hours, cores were harvested and analysed for ¹⁵N. Approximately 90% of the recovered isotope was in the upper Empodisma root layer. Seven weeks after tracer application, young shoots of Empodisma were significantly enriched whereas adjacent Sporadanthus shoots were not. The results confirm that species acquire nutrients from different rooting zones, with Empodisma accessing nutrients at the surface from rainfall and S. ferrugineus acquiring nutrients from deeper peat layers. Niche differentiation facilitates species co-existence, which, on a successional time scale, may be a mechanism for slowing the rate of competitive displacement.

text: Restiad bog development and nutrient dynamics of the dominant species Vegetation and peat in lowland restiad (dominated by Restionaceae) raised bogs on North Island (Waikato region) and Chatham Island, New Zealand, were sampled to investigate the main environmental controls of pattern and change. Vegetation classification based on a chronosequence of Waikato restiad bogs revealed a sequence from sedges, through Empodisma minus, the main peatforming restiad, to phases dominated by a second restiad, Sporadanthus ferrugineus. The sequence paralleled temporal successional patterns and was used for interpreting plant-nutrient dynamics along a successional gradient. As succession proceeds, von Post (an index of peat decomposition), total P, total N and % ash in peat decrease. Empodisma was considered to be the key species in restiad bog development. It is tolerant of a wide environmental range, establishing early in minerotrophic wetlands to initiate restiad bog development, and persisting through to late ombrotrophic phases. On Chatham Island, the ecological role of Sporadanthus traversii in restiad bog development is similar to Empodisma in Waikato, being the main peat former and occupying a wide environmental range. Peat under S. traversii had significantly higher total N, total K, available P, bulk density and von Post, and lower pH than Waikato peats under S. ferrugineus or Empodisma. This was attributed to a strong oceanic influence and long history of sea-bird nutrient inputs. 
Nutrient responses in the heath and restiad components of the bog were compared by measuring plant ¹⁵N natural abundance across N and P gradients. Heath shrubs revealed considerable isotopic variation (-2.03 to - 15.55 for Leptospermum scoparium), with foliar δ¹⁵N strongly positively correlated with P concentrations in foliage and peat. In contrast, restiad species revealed little isotopic variation, with Empodisma and S. traversii having δ¹⁵N levels around 0‰, and S. ferrugineus being significantly more depleted (mean -4.97‰). The differences in ii isotopic signatures between heath shrubs and restiads were linked to contrasting nutrient demands, acquisition mechanisms, and root morphology. Leptospermum shrubs on low nutrient peats were stunted, with low foliar %P and high N:P ratios, suggesting they were P-limited. The concurrence of δ¹⁵N depletion and %P in plant tissues suggests N fractionation is promoted by P limitation. In contrast, the constancy in δ¹⁵N of the restiad species through the nutrient gradients indicates these may not be P-limited. 
The contrasting δ¹⁵N signatures of co-habiting Empodisma and S. ferrugineus in late successional bogs suggest the species are accessing different sources of N. Empodisma has a thick layer of cluster roots overlying the deeper S. ferrugineus roots, and would be better positioned to intercept aerially derived N. The hypothesis that this root disposition allows Empodisma to preferentially access the primary N input from rainfall was tested using a ¹⁵N-enriched tracer. At plots codominated by Empodisma and S.ferrugineus, 1.6 mmoles m-2 of 99 atom% excess ¹⁵N as (NH4)2S04 was applied to the peat surface, followed by deionised water, simulating a rainfall event of 34 mm. After 5 hours, cores were harvested and analysed for ¹⁵N. Approximately 90% of the recovered isotope was in the upper Empodisma root layer. Seven weeks after tracer application, young shoots of Empodisma were significantly enriched whereas adjacent Sporadanthus shoots were not. The results confirm that species acquire nutrients from different rooting zones, with Empodisma accessing nutrients at the surface from rainfall and S. ferrugineus acquiring nutrients from deeper peat layers. Niche differentiation facilitates species co-existence, which, on a successional time scale, may be a mechanism for slowing the rate of competitive displacement.

year: 2005

title: A job, a dream or a trap? Multiple meanings for encore careers

authors: Simpson, Mary Louisa

subjects: aging

abstract: Governments and activists are interested in the ageing workforce, as both a problem and, 
potentially, an asset. Terms such as ‘positive ageing’ and ‘successful ageing’ are increasingly used rhetorically to (re)frame the working lives of elders, and demand careful examination. A recent entry in the discursive re-construction of work in later life is ‘encore careers’, which highlights retirement as a time when individuals choose to use their wealth of experience, engaging in  work that matters and makes meaningful contributions to society. This article reports on a study that used a multiple perspectives approach to analyse the discourse of elders engaged in encore  careers and managers who work with them.

text: A job, a dream or a trap? Multiple meanings for encore careers Governments and activists are interested in the ageing workforce, as both a problem and, 
potentially, an asset. Terms such as ‘positive ageing’ and ‘successful ageing’ are increasingly used rhetorically to (re)frame the working lives of elders, and demand careful examination. A recent entry in the discursive re-construction of work in later life is ‘encore careers’, which highlights retirement as a time when individuals choose to use their wealth of experience, engaging in  work that matters and makes meaningful contributions to society. This article reports on a study that used a multiple perspectives approach to analyse the discourse of elders engaged in encore  careers and managers who work with them.

year: 2012

title: Finding synergistic conservation values? Māori tikanga, science, resource management and law

authors: Simon, Katie

subjects: Indigenous knowledge

abstract: In this doctorate, I provide a balanced and collaborative approach to knowledge/value change between the contesting worldviews of indigenous knowledge and western science, termed 'synergistic'. My search for synergy is comparative and reconciliatory. This endeavours to overcome the popular pre-occupation with conflict and opposition. Rather, both difference and similarity are recognised. Through the comparison of such synergy, I argue that Māori development requires for its further advancement a focus not only on difference and conflict, but also on affinity and convergence.

My primary concern is to establish a better understanding of the synergistic, adaptive strategies or indigenous innovation of Māori kaitiaki, environmental stewards. I investigate conflicting and converging Māori and western scientific conservation and use values in Aotearoa/New Zealand  environmental governance and management regimes under the Resource Management Act 1991, with specific regard to indicator development. The balance of values were compared in ecological environmental governance, from five Aotearoa governmental authorities and three Māori river communities, utilising Māori and western social science methods. My focus on indicators pinpoints contesting knowledge/value change between the marginalisation of indigenous knowledge and dominance of western science. This seeks to highlight the potential viability of Māori kaitiakitanga, stewardship in global and national terms of sustainability.  

However, potential synergy is held back by a prevailing viewpoint of the indigenous worldview as backward, past-oriented and non-synergistic. An oppositional dogma predominates, which is a key problem to overcome. It spans world and national literature, resulting in considerable gaps in knowledge on synergy, conceptually, methodologically, empirically and analytically.  


This is addressed by an authoritative Māori synergistic standpoint from my own cultural lens and decolonised theorising, termed 'nuanced problem solving'. I articulate both worldviews in knowledge/value change through comparative, evolutionary, multi-dimensional, cross-cultural and inter-disciplinary research on synergy. My nuanced problem solving encapsulates the two main parts of the doctorate, whereby synergy is correlated between theory and social practice. Part one deals with value comparison in theory utilising high abstracted concepts and methods at the global level of environmental governance. Part two deals with value balance in social practice utilising medium abstracted and concrete empirical and analytical research at global, national, regional, district and cross-tribal levels of environmental governance. Potential synergy cross-cuts each part from high abstracted thought down and from the practical flax roots up. I argue that Māori advancement fluctuates between them. 

Drawing on cultural and theoretical leanings of the Māori synergistic standpoint, both a strong correlation with existing theory and expanded synergistic theorising was found. Due to the expansiveness of the research, these correlated findings only provide an embryonic understanding of potential synergy.

A postscript describes my other work on synergy with five external agencies concerning foreshore, lakeside, wastewater, land disposal and carbon marketing kaitiakitanga.  I argue that additional research on synergy is needed in order to further advance Māori.

text: Finding synergistic conservation values? Māori tikanga, science, resource management and law In this doctorate, I provide a balanced and collaborative approach to knowledge/value change between the contesting worldviews of indigenous knowledge and western science, termed 'synergistic'. My search for synergy is comparative and reconciliatory. This endeavours to overcome the popular pre-occupation with conflict and opposition. Rather, both difference and similarity are recognised. Through the comparison of such synergy, I argue that Māori development requires for its further advancement a focus not only on difference and conflict, but also on affinity and convergence.

My primary concern is to establish a better understanding of the synergistic, adaptive strategies or indigenous innovation of Māori kaitiaki, environmental stewards. I investigate conflicting and converging Māori and western scientific conservation and use values in Aotearoa/New Zealand  environmental governance and management regimes under the Resource Management Act 1991, with specific regard to indicator development. The balance of values were compared in ecological environmental governance, from five Aotearoa governmental authorities and three Māori river communities, utilising Māori and western social science methods. My focus on indicators pinpoints contesting knowledge/value change between the marginalisation of indigenous knowledge and dominance of western science. This seeks to highlight the potential viability of Māori kaitiakitanga, stewardship in global and national terms of sustainability.  

However, potential synergy is held back by a prevailing viewpoint of the indigenous worldview as backward, past-oriented and non-synergistic. An oppositional dogma predominates, which is a key problem to overcome. It spans world and national literature, resulting in considerable gaps in knowledge on synergy, conceptually, methodologically, empirically and analytically.  


This is addressed by an authoritative Māori synergistic standpoint from my own cultural lens and decolonised theorising, termed 'nuanced problem solving'. I articulate both worldviews in knowledge/value change through comparative, evolutionary, multi-dimensional, cross-cultural and inter-disciplinary research on synergy. My nuanced problem solving encapsulates the two main parts of the doctorate, whereby synergy is correlated between theory and social practice. Part one deals with value comparison in theory utilising high abstracted concepts and methods at the global level of environmental governance. Part two deals with value balance in social practice utilising medium abstracted and concrete empirical and analytical research at global, national, regional, district and cross-tribal levels of environmental governance. Potential synergy cross-cuts each part from high abstracted thought down and from the practical flax roots up. I argue that Māori advancement fluctuates between them. 

Drawing on cultural and theoretical leanings of the Māori synergistic standpoint, both a strong correlation with existing theory and expanded synergistic theorising was found. Due to the expansiveness of the research, these correlated findings only provide an embryonic understanding of potential synergy.

A postscript describes my other work on synergy with five external agencies concerning foreshore, lakeside, wastewater, land disposal and carbon marketing kaitiakitanga.  I argue that additional research on synergy is needed in order to further advance Māori.

year: 2007