title: Conifer-angiosperm interactions: Physiological ecology and life history.

authors: Lusk, Christopher H.

abstract: Worldwide, conifers are most successful on sites subject to chronic stresses that limit productivity (low temperatures, nutrient poverty, poor drainage). They are poorly represented in the lowland tropics but are often important in Montane tropical forests. Here I explore some functional differences between leaf and xylem traits of conifer and angiosperm trees and their implications for the distributions of these two groups on environmental gradients. Analysis of a global data set shows that compared with angiosperm trees, conifers tend to have longer-lived leaves with greater mass per area (LMA) and lower mass-based photosynthetic capacity. As leaf life span is thought to be the main determinant of nutrient retention time, the prominence of conifers on infertile soils worldwide is at least partly attributable to thrifty use of nutrients through long leaf life spans. Furthermore, because leaf life span correlates with litter decomposition rates, these leaf trait differences could potentially influence the competitive balance between conifers and angiosperms via positive feedbacks on nutrient cycling. Although scaling of leaf life span with LMA is similar in the two groups, angiosperms achieve slightly longer leaf life spans than conifers of similar photosynthetic capacity. This might be caused by less-efficient leaf display in conifers, resulting in the useful life span of leaves being curtailed by self-shading. Representatives of both lineages have narrower conduits in the temperate zone than in the lowland tropics/subtropics, reflecting selection for resistance to freeze-thaw embolism in cold climates. However, conduit diameters of conifers and angiosperm trees differ more in tropical and subtropical forests than at higher latitudes. This probably reflects mechanical constraints on maximum tracheid diameters in the homoxylous wood of conifers, preventing this group from producing the highly conductive wood typical of fast-growing angiosperm pioneers in tropical forests. This pattern might explain why coexistence of conifers and angiosperms is more common in temperate forests and on tropical mountains than in the lowland tropics. Impairment of angiosperm carbon gain by freeze-thaw embolism during cold weather may further narrow performance differences between the two lineages on temperate sites. Differences in canopy residence time probably deserve more attention as a determinant of conifer-angiosperm coexistence in many temperate forests, the longer life span of conifers compensating for infrequent recruitment.

text: Conifer-angiosperm interactions: Physiological ecology and life history. Worldwide, conifers are most successful on sites subject to chronic stresses that limit productivity (low temperatures, nutrient poverty, poor drainage). They are poorly represented in the lowland tropics but are often important in Montane tropical forests. Here I explore some functional differences between leaf and xylem traits of conifer and angiosperm trees and their implications for the distributions of these two groups on environmental gradients. Analysis of a global data set shows that compared with angiosperm trees, conifers tend to have longer-lived leaves with greater mass per area (LMA) and lower mass-based photosynthetic capacity. As leaf life span is thought to be the main determinant of nutrient retention time, the prominence of conifers on infertile soils worldwide is at least partly attributable to thrifty use of nutrients through long leaf life spans. Furthermore, because leaf life span correlates with litter decomposition rates, these leaf trait differences could potentially influence the competitive balance between conifers and angiosperms via positive feedbacks on nutrient cycling. Although scaling of leaf life span with LMA is similar in the two groups, angiosperms achieve slightly longer leaf life spans than conifers of similar photosynthetic capacity. This might be caused by less-efficient leaf display in conifers, resulting in the useful life span of leaves being curtailed by self-shading. Representatives of both lineages have narrower conduits in the temperate zone than in the lowland tropics/subtropics, reflecting selection for resistance to freeze-thaw embolism in cold climates. However, conduit diameters of conifers and angiosperm trees differ more in tropical and subtropical forests than at higher latitudes. This probably reflects mechanical constraints on maximum tracheid diameters in the homoxylous wood of conifers, preventing this group from producing the highly conductive wood typical of fast-growing angiosperm pioneers in tropical forests. This pattern might explain why coexistence of conifers and angiosperms is more common in temperate forests and on tropical mountains than in the lowland tropics. Impairment of angiosperm carbon gain by freeze-thaw embolism during cold weather may further narrow performance differences between the two lineages on temperate sites. Differences in canopy residence time probably deserve more attention as a determinant of conifer-angiosperm coexistence in many temperate forests, the longer life span of conifers compensating for infrequent recruitment.

year: 2011

title: Moisture sensitivity and compressive performance of 3D-printed cellulose-biopolyester foam lattices

authors: McDonald-Wharry, John

subjects: Science & Technology

abstract: Biobased, foam-like polyester composite materials were 3D-printed from a thermoset paste formulation. This paste formulation was composed of sebacic acid, glycerol, citric acid, and cellulose nanocrystals in water and ethanol with potassium chloride as a salt porogen. Thin walls and lattices were 3D-printed with geometry selected to facilitate post-printing processes such as water removal during polyester curing and the post-curing removal of the salt porogen. The compressive performance of these moisture-sensitive lattice structures was investigated after conditioning at different humidity levels and by water immersion. Finite element analysis was used to simulate the compressive performance of these porous lattice structures using a crushable foam material model. Addition of plant triglyceride oils from sunflower and coconut were trialled to modify the compressive performance and moisture sensitivity. Addition of 5 wt% coconut oil to the formulation prior to 3D-printing was found to lower the cured material’s stiffness under dry conditions while increasing the compressive plateau strength of the lattice structures after water immersion.

text: Moisture sensitivity and compressive performance of 3D-printed cellulose-biopolyester foam lattices Biobased, foam-like polyester composite materials were 3D-printed from a thermoset paste formulation. This paste formulation was composed of sebacic acid, glycerol, citric acid, and cellulose nanocrystals in water and ethanol with potassium chloride as a salt porogen. Thin walls and lattices were 3D-printed with geometry selected to facilitate post-printing processes such as water removal during polyester curing and the post-curing removal of the salt porogen. The compressive performance of these moisture-sensitive lattice structures was investigated after conditioning at different humidity levels and by water immersion. Finite element analysis was used to simulate the compressive performance of these porous lattice structures using a crushable foam material model. Addition of plant triglyceride oils from sunflower and coconut were trialled to modify the compressive performance and moisture sensitivity. Addition of 5 wt% coconut oil to the formulation prior to 3D-printing was found to lower the cured material’s stiffness under dry conditions while increasing the compressive plateau strength of the lattice structures after water immersion.

year: 2021

title: Beyond ethics to morality: Choices and relationships in bicultural research settings

authors: Furness, Jane Amanda

subjects: Indigenous methodologies

abstract: Knowledge of ourselves as cultural beings, of the values and beliefs of those with whom we work, and of the history of relations among those in our work settings are essential for community and applied social psychologists. In New Zealand, research by non-Maori involving Maori has often mirrored the harmful colonising practices of the nation’s wider history. In response, several frameworks have been developed setting out conditions and guidelines in which non-Maori might conduct research in Maori settings responsibly and usefully. Nevertheless, views differ on the ways, and extent to which, non-Maori might be involved. Most guidelines do not provide answers to ethical nuances that may arise. This article discusses the experiences of a non-Maori community psychologist engaging in research with Maori participants in a bicultural, but predominantly Maori, school-based community education setting. Insight is provided into how kaupapa Maori approaches were applied in research that was valuable to the community.

text: Beyond ethics to morality: Choices and relationships in bicultural research settings Knowledge of ourselves as cultural beings, of the values and beliefs of those with whom we work, and of the history of relations among those in our work settings are essential for community and applied social psychologists. In New Zealand, research by non-Maori involving Maori has often mirrored the harmful colonising practices of the nation’s wider history. In response, several frameworks have been developed setting out conditions and guidelines in which non-Maori might conduct research in Maori settings responsibly and usefully. Nevertheless, views differ on the ways, and extent to which, non-Maori might be involved. Most guidelines do not provide answers to ethical nuances that may arise. This article discusses the experiences of a non-Maori community psychologist engaging in research with Maori participants in a bicultural, but predominantly Maori, school-based community education setting. Insight is provided into how kaupapa Maori approaches were applied in research that was valuable to the community.

year: 2013