title: The whole-plant compensation point as a measure of juvenile tree light requirements

authors: Lusk, Christopher H.

subjects: forest dynamics

abstract: 1.	Although ‘shade tolerance’ has featured prominently in the vocabulary of foresters and ecologists for a century, we have yet to agree on a standardized method for quantifying this elusive property. The ‘whole-plant compensation point’, interpolated from stem growth measurements across a wide range of light environments, has been proposed as a simple, robust measure of species shade tolerance. Others have argued that shade tolerance is primarily a function of differential ability to survive periods of slow growth (‘suppression’), implying that measurements of survival are vital.
2.	We measured growth of juveniles (500–1000 mm tall) of five evergreen trees over 12 months in a cool-temperate rain forest in New Zealand, to determine whether whole-plant compensation points predicted species differences in occupancy of understorey light environments, which were quantified using hemispherical photography.
3.	The five species encompassed 3•5-fold variation in whole-plant compensation points. Compensation points of most species fell within the first quartile of the distribution of light environments occupied by juveniles; they were also correlated with low-light mortality rates of juveniles, estimated from permanent plot data archived in the National Vegetation Survey Databank. Compensation points were also significantly positively correlated with height growth rates in high light, confirming the presence of the growth vs. shade tolerance trade-off detected in many other forest tree assemblages.
4.	Results show that, in temperate evergreen forests, the whole-plant compensation point distinguishes reliably between species of differing shade tolerance. Excepting situations involving parameterization of demographic models, shade tolerance can therefore be assessed without survival measurements. However, estimating whole-plant compensation points may prove more difficult in deciduous forests, where seasonal variation in understorey light transmission poses additional challenges.

text: The whole-plant compensation point as a measure of juvenile tree light requirements 1.	Although ‘shade tolerance’ has featured prominently in the vocabulary of foresters and ecologists for a century, we have yet to agree on a standardized method for quantifying this elusive property. The ‘whole-plant compensation point’, interpolated from stem growth measurements across a wide range of light environments, has been proposed as a simple, robust measure of species shade tolerance. Others have argued that shade tolerance is primarily a function of differential ability to survive periods of slow growth (‘suppression’), implying that measurements of survival are vital.
2.	We measured growth of juveniles (500–1000 mm tall) of five evergreen trees over 12 months in a cool-temperate rain forest in New Zealand, to determine whether whole-plant compensation points predicted species differences in occupancy of understorey light environments, which were quantified using hemispherical photography.
3.	The five species encompassed 3•5-fold variation in whole-plant compensation points. Compensation points of most species fell within the first quartile of the distribution of light environments occupied by juveniles; they were also correlated with low-light mortality rates of juveniles, estimated from permanent plot data archived in the National Vegetation Survey Databank. Compensation points were also significantly positively correlated with height growth rates in high light, confirming the presence of the growth vs. shade tolerance trade-off detected in many other forest tree assemblages.
4.	Results show that, in temperate evergreen forests, the whole-plant compensation point distinguishes reliably between species of differing shade tolerance. Excepting situations involving parameterization of demographic models, shade tolerance can therefore be assessed without survival measurements. However, estimating whole-plant compensation points may prove more difficult in deciduous forests, where seasonal variation in understorey light transmission poses additional challenges.

year: 2013

title: Exploring the Possibility of an Intergenerational Right to Return to Earth

authors: Brennan, Anna

abstract: If human civilisation realises its grand ambitions to establish extraterrestrial human settlements on Mars in the not-so-distant future, how will human rights apply and be enforced? Rather than States, it is thought that space companies such as SpaceX, Blue Origin and the Sierra Nevada Corporation will be the first to establish extraterrestrial settlements. Rapid technological developments over the last decade mean that these ambitions are no longer science fiction. This article considers the scope of the right to freedom of movement in outer space, especially the right to return to Earth. Due to the perilous nature of the journey from Earth to Mars and the harsh environment in which the first settlements will be established, this article considers whether there are any legitimate and, indeed,
permissible circumstances where the right to return to Earth will be restricted. The final part of this article will explore the possibility that future descendants of the first wave of settlers to Mars will have an intergenerational right to return to Earth
despite having been born on the Red Planet.

text: Exploring the Possibility of an Intergenerational Right to Return to Earth If human civilisation realises its grand ambitions to establish extraterrestrial human settlements on Mars in the not-so-distant future, how will human rights apply and be enforced? Rather than States, it is thought that space companies such as SpaceX, Blue Origin and the Sierra Nevada Corporation will be the first to establish extraterrestrial settlements. Rapid technological developments over the last decade mean that these ambitions are no longer science fiction. This article considers the scope of the right to freedom of movement in outer space, especially the right to return to Earth. Due to the perilous nature of the journey from Earth to Mars and the harsh environment in which the first settlements will be established, this article considers whether there are any legitimate and, indeed,
permissible circumstances where the right to return to Earth will be restricted. The final part of this article will explore the possibility that future descendants of the first wave of settlers to Mars will have an intergenerational right to return to Earth
despite having been born on the Red Planet.

year: 2024

title: Gendered geographies of resistance, resilience and reworking in Aotearoa feminist geography scholarship

authors: Adams-Hutcheson, Gail

abstract: Aotearoa New Zealand feminist geographies involve alliances of connected and vibrant researchers who pay close attention to the politics of knowledge production, power, intersectionality and decolonisation. Safe spaces to speak and write together have been nurtured over time ‘down under’ due to a collective politics of care and mentoring. This special issue demonstrates the strength of collective thinking on resistance, resilience and reworking contemporary geographical practice in Aotearoa. The four empirically based and theoretically informed articles develop new thinking about resistance to colonialism, patriarchy, racism, metricisation and oppression. These critical articles contribute to feminist geographical knowledges both locally and globally.

text: Gendered geographies of resistance, resilience and reworking in Aotearoa feminist geography scholarship Aotearoa New Zealand feminist geographies involve alliances of connected and vibrant researchers who pay close attention to the politics of knowledge production, power, intersectionality and decolonisation. Safe spaces to speak and write together have been nurtured over time ‘down under’ due to a collective politics of care and mentoring. This special issue demonstrates the strength of collective thinking on resistance, resilience and reworking contemporary geographical practice in Aotearoa. The four empirically based and theoretically informed articles develop new thinking about resistance to colonialism, patriarchy, racism, metricisation and oppression. These critical articles contribute to feminist geographical knowledges both locally and globally.

year: 2022-11-22