title: Nutritional niche separation in coexisting bog species demonstrated by ¹⁵N-enriched simulated rainfall

authors: Clarkson, Beverley R.

subjects: niche separation

abstract: Empodisma minus and Sporadanthus ferrugineus (both Restionaceae) coexist in New Zealand raised bogs, yet Sporadanthus have significantly more depleted ¹⁵N natural abundance signatures than coexisting Empodisma. Their root systems are spatially separated with Empodisma having a thick surface layer of about 50 mm of cluster roots overlying the deeper Sporadanthus roots. We hypothesized this root displacement allows Empodisma to preferentially access the primary N input from rainfall, thus establishing niche separation, and tested this using tracer stable isotopes. We aerially applied 1.6 mmol m⁻² of ¹⁵N as (NH₄)₂SO₄ chased by deionized water to simulate a rainfall event of 34 L m⁻². Root/peat matrix cores were harvested after 5 h and analysed for ¹⁵N uptake. Approximately 80% of the tracer applied was recovered in the cores, with 90% of this recovered in the upper Empodisma cluster root layer. Seven weeks after application, young shoots of Empodisma were significantly enriched (mean δ15N = +7.21‰; reference = −0.42‰), whereas those of coexisting Sporadanthus were not (mean δ15N = −2.76‰; reference = −4.24‰). However, we were unable to quantify the ¹⁵N uptake because of the dilution effect of the large biomass. We calculated the contribution of biological nitrogen fixation as a possible alternative source of N in achieving niche separation. The acetylene reduction assay showed minor amounts of nitrogenase activity are associated with Empodisma and Sporadanthus roots (equivalent to 0.045 ± 0.019 and 0.104 ± 0.017 kg N ha⁻¹ year⁻¹respectively). Our results suggest that the species acquire nutrients from different rooting zones, with Empodisma accessing nutrients at the surface from rainfall and Sporadanthus accessing nutrients from mineralization in deeper peat layers. Such niche differentiation probably facilitates species coexistence and may provide a mechanism for slowing the rate of competitive displacement during long-term succession.

text: Nutritional niche separation in coexisting bog species demonstrated by ¹⁵N-enriched simulated rainfall Empodisma minus and Sporadanthus ferrugineus (both Restionaceae) coexist in New Zealand raised bogs, yet Sporadanthus have significantly more depleted ¹⁵N natural abundance signatures than coexisting Empodisma. Their root systems are spatially separated with Empodisma having a thick surface layer of about 50 mm of cluster roots overlying the deeper Sporadanthus roots. We hypothesized this root displacement allows Empodisma to preferentially access the primary N input from rainfall, thus establishing niche separation, and tested this using tracer stable isotopes. We aerially applied 1.6 mmol m⁻² of ¹⁵N as (NH₄)₂SO₄ chased by deionized water to simulate a rainfall event of 34 L m⁻². Root/peat matrix cores were harvested after 5 h and analysed for ¹⁵N uptake. Approximately 80% of the tracer applied was recovered in the cores, with 90% of this recovered in the upper Empodisma cluster root layer. Seven weeks after application, young shoots of Empodisma were significantly enriched (mean δ15N = +7.21‰; reference = −0.42‰), whereas those of coexisting Sporadanthus were not (mean δ15N = −2.76‰; reference = −4.24‰). However, we were unable to quantify the ¹⁵N uptake because of the dilution effect of the large biomass. We calculated the contribution of biological nitrogen fixation as a possible alternative source of N in achieving niche separation. The acetylene reduction assay showed minor amounts of nitrogenase activity are associated with Empodisma and Sporadanthus roots (equivalent to 0.045 ± 0.019 and 0.104 ± 0.017 kg N ha⁻¹ year⁻¹respectively). Our results suggest that the species acquire nutrients from different rooting zones, with Empodisma accessing nutrients at the surface from rainfall and Sporadanthus accessing nutrients from mineralization in deeper peat layers. Such niche differentiation probably facilitates species coexistence and may provide a mechanism for slowing the rate of competitive displacement during long-term succession.

year: 2009

title: Relational and collective excellence: unfolding the potential of Pacific early career researchers

authors: Allen, Jean M. Uasika

subjects: relational excellence

abstract: As Pacific early career researchers (ECRs), relational interconnections and engagement are at the heart of our collective responsibilities to each other. Although we share a mutual responsibility to our research communities (in academia and industry), each Pacific ECR is unique in our field of research and genealogical connections to the Pacific. This paper engages the Indigenous storywork methodology to capture, negotiate, and make meaningful links between our research experiences and relational excellence. This methodological approach reveals thematic elements of respect, responsibility, reciprocity, reverence, holism, interrelatedness, and synergy are woven throughout the paper to highlight our collective va-relationality and potential as ECRs. Our collaborative approach to defining and engaging with Pacific research creates new and innovative possibilities for Indigenous and Pacific research excellence.

text: Relational and collective excellence: unfolding the potential of Pacific early career researchers As Pacific early career researchers (ECRs), relational interconnections and engagement are at the heart of our collective responsibilities to each other. Although we share a mutual responsibility to our research communities (in academia and industry), each Pacific ECR is unique in our field of research and genealogical connections to the Pacific. This paper engages the Indigenous storywork methodology to capture, negotiate, and make meaningful links between our research experiences and relational excellence. This methodological approach reveals thematic elements of respect, responsibility, reciprocity, reverence, holism, interrelatedness, and synergy are woven throughout the paper to highlight our collective va-relationality and potential as ECRs. Our collaborative approach to defining and engaging with Pacific research creates new and innovative possibilities for Indigenous and Pacific research excellence.

year: 2022-08-04

title: Māori men: An indigenous psychological perspective on the interconnected self

authors: Rua, Mohi

subjects: Māori men

abstract: The positive relational practices of Māori men are seldom explored in academic research. Responding to this gap in the literature, this article explores how Māori men negotiate a positive sense of self and relationships. This research is guided by kaupapa Māori research practice, Māori cultural concepts, and relational understandings of identity and wellbeing. Our ethnographic approach involved direct observations, engagement in shared cultural practices and narrative interviews. During these interactions, participating men invoked a positive sense of self through accounts of belonging, reciprocity, dialogue, intimacy, and care for themselves, their whānau, and traditions. We found that Māori men's identities are negotiated through interactions with whānau (immediate and extended family), and particular places and practices. Our participants demonstrated how Māori men’s positive self-constructions are fundamentally interconnected with other people, cultural traditions, socio-cultural practices, physical and symbolic places, as well as their own health and the health of those around them.

text: Māori men: An indigenous psychological perspective on the interconnected self The positive relational practices of Māori men are seldom explored in academic research. Responding to this gap in the literature, this article explores how Māori men negotiate a positive sense of self and relationships. This research is guided by kaupapa Māori research practice, Māori cultural concepts, and relational understandings of identity and wellbeing. Our ethnographic approach involved direct observations, engagement in shared cultural practices and narrative interviews. During these interactions, participating men invoked a positive sense of self through accounts of belonging, reciprocity, dialogue, intimacy, and care for themselves, their whānau, and traditions. We found that Māori men's identities are negotiated through interactions with whānau (immediate and extended family), and particular places and practices. Our participants demonstrated how Māori men’s positive self-constructions are fundamentally interconnected with other people, cultural traditions, socio-cultural practices, physical and symbolic places, as well as their own health and the health of those around them.

year: 2017