title: Extremely low lichen growth rates in Taylor Valley, Dry Valleys, continental Antarctica

authors: Green, T.G. Allan

subjects: lichenometry

abstract: Estimates of lichen growth rates based on the measurements of several thalli at any site do not exist for continental Antarctica. However, the very limited existing data suggest that lichen growth rate may be a good indicator of climate change in Antarctica. We present measurements made on thalli of the lichen Buellia frigida Darb. growing in the Dry Valleys, Southern Victoria Land, continental Antarctica, which appear to have some of the slowest radial growth rates yet measured. Photographs of thalli at three different sites were analysed for growth over a 25-year period using nano-GIS techniques. At one site, Mt. Falconer Summit, the lichens had a mean growth rate of 0.0052 mm year-1 with one individual as low as 0.0036 mm year-1. Thalli at the other two sites had significantly higher mean growth rates, 0.0136 mm year-1 at Mt. Falconer Ridge and 0.0118 mm year-1 at Rhone Bench. Assuming a constant growth rate, thalli at Mt. Falconer Summit had a mean age of 5,367 years, whilst the thalli at the other two sites were much younger, 840–1,026 years. We suggest that the different ages represent the appearance of new substrate for colonisation following climate changes in the Dry Valleys that altered the amount and duration of snow. The results confirm that lichen growth rate differs by almost two orders of magnitude over a latitudinal range of 15 degrees from south to north across Antarctica.

text: Extremely low lichen growth rates in Taylor Valley, Dry Valleys, continental Antarctica Estimates of lichen growth rates based on the measurements of several thalli at any site do not exist for continental Antarctica. However, the very limited existing data suggest that lichen growth rate may be a good indicator of climate change in Antarctica. We present measurements made on thalli of the lichen Buellia frigida Darb. growing in the Dry Valleys, Southern Victoria Land, continental Antarctica, which appear to have some of the slowest radial growth rates yet measured. Photographs of thalli at three different sites were analysed for growth over a 25-year period using nano-GIS techniques. At one site, Mt. Falconer Summit, the lichens had a mean growth rate of 0.0052 mm year-1 with one individual as low as 0.0036 mm year-1. Thalli at the other two sites had significantly higher mean growth rates, 0.0136 mm year-1 at Mt. Falconer Ridge and 0.0118 mm year-1 at Rhone Bench. Assuming a constant growth rate, thalli at Mt. Falconer Summit had a mean age of 5,367 years, whilst the thalli at the other two sites were much younger, 840–1,026 years. We suggest that the different ages represent the appearance of new substrate for colonisation following climate changes in the Dry Valleys that altered the amount and duration of snow. The results confirm that lichen growth rate differs by almost two orders of magnitude over a latitudinal range of 15 degrees from south to north across Antarctica.

year: 2011

title: A numerical model to simulate the formation and subsequent evolution of tidal channel networks

authors: van Maanen, Barend

subjects: Long-term morphological evolution

abstract: We present a numerical model that simulates morphological change as a result of the interactions between hydrodynamics, sediment transport and bed elevation change. Numerical simulations indicate that these morphodynamic interactions can lead to the initiation of tidal channels and potentially give rise to large-scale channel networks. We perform a sensitivity analysis to show how model outcome is sensitive to the numerical scheme adopted, hydrodynamic and morphological time-steps, and initial bathymetry. Furthermore, the formation of tidal channels and intertidal areas affects both the large-scale flow patterns, as well as the asymmetry between flood- and ebb-tidal currents.

text: A numerical model to simulate the formation and subsequent evolution of tidal channel networks We present a numerical model that simulates morphological change as a result of the interactions between hydrodynamics, sediment transport and bed elevation change. Numerical simulations indicate that these morphodynamic interactions can lead to the initiation of tidal channels and potentially give rise to large-scale channel networks. We perform a sensitivity analysis to show how model outcome is sensitive to the numerical scheme adopted, hydrodynamic and morphological time-steps, and initial bathymetry. Furthermore, the formation of tidal channels and intertidal areas affects both the large-scale flow patterns, as well as the asymmetry between flood- and ebb-tidal currents.

year: 2011

title: Growth out of loss: The urban discourses of literatures of the Native American and Māori literary renaissance

authors: Waterman, Jason

subjects: New Zealand

abstract: The seeds of the Native American and Māori Renaissance eras germinated amid sweeping changes in the years immediately following World War II, a time when urbanization and the consequent separation of indigenous peoples from community networks represented a major threat to culturally embedded certainties and destabilized romanticized notions of the past. This article explores parallels between the ways in which Native American and Māori literatures reflect the impact of urbanization at the height of this era and the contribution the authors make to the positive cultural growth that defines their respective renaissance periods.

text: Growth out of loss: The urban discourses of literatures of the Native American and Māori literary renaissance The seeds of the Native American and Māori Renaissance eras germinated amid sweeping changes in the years immediately following World War II, a time when urbanization and the consequent separation of indigenous peoples from community networks represented a major threat to culturally embedded certainties and destabilized romanticized notions of the past. This article explores parallels between the ways in which Native American and Māori literatures reflect the impact of urbanization at the height of this era and the contribution the authors make to the positive cultural growth that defines their respective renaissance periods.

year: 2009-09