Showing papers by "Sharon A. Robinson published in 2012"

Antarctic Climate Change and the Environment: an Update.

Abstract: We present an update of the ‘key points’ from the Antarctic Climate Change and the Environment (ACCE) report that was published by the Scientific Committee on Antarctic Research (SCAR) in 2009. We summarise subsequent advances in knowledge concerning how the climates of the Antarctic and Southern Ocean have changed in the past, how they might change in the future, and examine the associated impacts on the marine and terrestrial biota. We also incorporate relevant material presented by SCAR to the Antarctic Treaty Consultative Meetings, and make use of emerging results that will form part of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report

Radiocarbon bomb spike reveals biological effects of Antarctic climate change

Abstract: The Antarctic has experienced major changes in temperature, wind speed and stratospheric ozone levels during the last 50 years. However, until recently continental Antarctica appeared to be little impacted by climate warming, thus biological changes were predicted to be relatively slow. Detecting the biological effects of Antarctic climate change has been hindered by the paucity of long-term data sets, particularly for organisms that have been exposed to these changes throughout their lives. We show that radiocarbon signals are preserved along shoots of the dominant Antarctic moss flora and use these to determine accurate growth rates over a period of several decades, allowing us to explore the influence of environmental variables on growth and providing a dramatic demonstration of the effects of climate change. We have generated detailed 50-year growth records for C eratodon purpureus and three other Antarctic moss species using the 1960s radiocarbon bomb spike. Our growth rate and stable carbon isotope ( δ 13 C ) data show that C . purpureus ’ growth rates are correlated with key climatic variables, and furthermore that the observed effects of climate variation on growth are mediated through changes in water availability. Our results indicate the timing and balance between warming, high-wind speeds and elevated UV fluxes may determine the fate of these mosses and the associated communities that form oases of Antarctic biodiversity.

Using a micro-UAV for ultra-high resolution multi-sensor observations of Antarctic moss beds

Abstract: This study is the first to use an Unmanned Aerial Vehicle (UAV) for mapping moss beds in Antarctica. Mosses can be used as indicators for the regional effects of climate change. Mapping and monitoring their extent and health is therefore important. UAV aerial photography provides ultra-high resolution spatial data for this purpose. We developed a technique to extract an extremely dense 3D point cloud from overlapping UAV aerial photography based on structure from motion (SfM) algorithms. The combination of SfM and patch-based multi-view stereo image vision algorithms resulted in a 2 cm resolution digital terrain model (DTM). This detailed topographic information combined with vegetation indices derived from a 6-band multispectral sensor enabled the assessment of moss bed health. This novel UAV system has allowed us to map different environmental characteristics of the moss beds at ultra-high resolution providing us with a better understanding of these fragile Antarctic ecosystems. The paper provides details on the different UAV instruments and the image processing framework resulting in DEMs, vegetation indices, and terrain derivatives.

Canopy conundrums: building on the Biosphere 2 experience to scale measurements of inner and outer canopy photoprotection from the leaf to the landscape

Abstract: Recognising that plant leaves are the fundamental productive units of terrestrial vegetation and the complexity of different environments in which they must function, this review considers a few of the ways in which these functions may be measured and potentially scaled to the canopy. Although canopy photosynthetic productivity is clearly the sum of all leaves in the canopy, we focus on the quest for ‘economical insights’ from measurements that might facilitate integration of leaf photosynthetic activities into canopy performance, to better inform modelling based on the ‘insights of economics’. It is focussed on the reversible downregulation of photosynthetic efficiency in response to light environment and stress and summarises various xanthophyll-independent and dependent forms of photoprotection within the inner and outer canopy of woody plants. Two main themes are developed. First, we review experiments showing the retention of leaves that grow old in the shade may involve more than the ‘payback times’ required to recover the costs of their construction and maintenance. In some cases at least, retention of these leaves may reflect selection for distinctive properties that contribute to canopy photosynthesis through utilisation of sun flecks or provide ‘back up’ capacity following damage to the outer canopy. Second, we report experiments offering hope that remote sensing of photosynthetic properties in the outer canopy (using chlorophyll fluorescence and spectral reflectance technologies) may overcome problems of access and provide integrated measurements of these properties in the canopy as a whole. Finding appropriate tools to scale photosynthesis from the leaf to the landscape still presents a challenge but this synthesis identifies some measurements and criteria in the laboratory and the field that improve our understanding of inner and outer canopy processes.

From ecophysiology to phenomics: some implications of photoprotection and shade–sun acclimation in situ for dynamics of thylakoids in vitro

Abstract: Half a century of research into the physiology and biochemistry of sun–shade acclimation in diverse plants has provided reality checks for contemporary understanding of thylakoid membrane dynamics. This paper reviews recent insights into photosynthetic efficiency and photoprotection from studies of two xanthophyll cycles in old shade leaves from the inner canopy of the tropical trees Inga sapindoides and Persea americana (avocado). It then presents new physiological data from avocado on the time frames of the slow coordinated photosynthetic development of sink leaves in sunlight and on the slow renovation of photosynthetic properties in old leaves during sun to shade and shade to sun acclimation. In so doing, it grapples with issues in vivo that seem relevant to our increasingly sophisticated understanding of ΔpH-dependent, xanthophyll-pigment-stabilized non-photochemical quenching in the antenna of PSII in thylakoid membranes in vitro.

Bryophyte species composition over moisture gradients in the Windmill Islands, East Antarctica: development of a baseline for monitoring climate change impacts

Abstract: Extreme environmental conditions prevail on the Antarctic continent and limit plant diversity to cryptogamic communities, dominated by bryophytes and lichens. Even small abiotic shifts, associated with climate change, are likely to have pronounced impacts on these communities that currently exist at their physiological limit of survival. Changes to moisture availability, due to precipitation shifts or alterations to permanent snow reserves, will most likely cause greatest impact. In order to establish a baseline for determining the effect of climate change on continental Antarctic terrestrial communities and to better understand bryophyte species distributions in relation to moisture in a floristically important Antarctic region, this study surveyed finescale bryophyte patterns and turf water and nutrient contents along community gradients in the Windmill Islands, East Antarctica. The survey found that the Antarctic endemic, Schistidium antarctici, dominated the wettest habitats, Bryum pseudotriquetrum di...