Abstracts on Global Climate Change

Nov 2004

Mineral stress: the missing link in understanding how global climate change will affect plants in real world soils

Lynch, JP St Clair, SB


Many natural and agricultural ecosystems are characterized by sub-optimal availability of mineral nutrients and ion toxicities. Mineral stresses are likely to have important, complex, and poorly understood interactions with global climate change variables. For example, most terrestrial vegetation is supported by weathered soils with some combination of low P, low Ca, Al toxicity, and Mn toxicity. Each of these stresses has complex, yet distinct, interactions with global change variables, making it very difficult to predict how plants in these environments will respond to future climate scenarios. Important, yet poorly understood, interactions include the effects of transpiration on root acquisition of soluble nutrients, particularly Ca and Si, the effects of altered root architecture on the acquisition of immobile nutrients, particularly P, the effects of altered root exudate production on Al toxicity and transition metal acquisition, and the interaction of photochemical processes with transition metal availability. The interaction of Mn toxicity with light intensity and other global change variables is discussed as an example of the complexity and potential importance of these relationships. Current conceptual models of plant response to multiple resource limitations are inadequate. Furthermore, substantial genetic variation exists in plant responses to mineral stress, and traits improving adaptation to one stress may incur tradeoffs for adaptation to other stresses. Root traits under quantitative genetic control are of central importance in adaptation to many mineral stresses. An integration of quantitative genetics with mechanistic and conceptual models of plant response to mineral stresses is needed if we are to understand plant response to global change in real-world soils. (C) 2004 Elsevier B.V. All rights reserved.

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Heat stress induces different forms of cell death in sea anemones and their endosymbiotic algae depending on temperature and duration

Dunn, SR Thomason, JC Le Tissier, MDA Bythell, JC


Bleaching of reef building corals and other symbiotic cnidarians due to the loss of their dinoflagellate algal symbionts (=zooxanthellae), and/or their photosynthetic pigments, is a common sign of environmental stress. Mass bleaching events are becoming an increasingly important cause of mortality and reef degradation on a global scale, linked by many to global climate change. However, the cellular mechanisms of stress-induced bleaching remain largely unresolved. In this study, the frequency of apoptosis-like and necrosis-like cell death was determined in the symbiotic sea anemone Aiptasia sp. using criteria that had previously been validated for this symbiosis as indicators of programmed cell death (PCD) and necrosis. Results indicate that PCD and necrosis occur simultaneously in both host tissues and zooxanthellae subject to environmentally relevant doses of heat stress. Frequency of PCD in the anemone endoderm increased within minutes of treatment. Peak rates of apoptosis-like cell death in the host were coincident with the timing of loss of zooxanthellae during bleaching. The proportion of apoptosis-like host cells subsequently declined while cell necrosis increased. In the zooxanthellae, both apoptosis-like and necrosis-like activity increased throughout the duration of the experiment (6 days), dependent on temperature dose. A stress-mediated PCD pathway is an important part of the thermal stress response in the sea anemone symbiosis and this study suggests that PCD may play different roles in different components of the symbiosis during bleaching.

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Investigation of plasma irregularity sources associated with charged dust in the earth’s mesosphere

Scales, WA Ganguli, G


Noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs) are two phenomena at the forefront of near earth space science. NLCs are high altitude clouds in the earth’s mesosphere that are formed from aerosol particles. The increase in the occurence of NLCs over time is believed to have profound implications on global climate change. PMSEs are believed to be related to NLCs and are strong radar echoes from mesospheric turbulence in the 50 MHz to 1.3 GHz range. Currently, there is no universally accepted explanation for the irregularities thought to produce PMSEs. Recent simultaneous sounding rocket, radar, and lidar observations of NLCs and PMSEs have provided a more detailed description of the electrodynamics and plasma configuration inside NLCs and the relationship to PMSEs. Particularly important is the simultaneous observation of charged aerosols, electron depletions, and small-scale electric field irregularities in the PMSE generation region. This work considers the consequences of the recent experimental observations on ultimately understanding the generation mechanism for PMSEs and the relationship to NLCs. A model for the electrodynamics and plasma configuration in the charged aerosol boundary layer will be described that indicates that plasma flows are expected to exist in the equilibrium. The possible role of these plasma flows in producing electron turbulence and irregularities in the charged aerosol boundary layer that may ultimately result in PMSEs is discussed. (C) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

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Is climate change affecting wolf populations in the High Arctic?

Mech, LD


Gobal climate change may affect wolves in Canada’s High Arctic (80degrees N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However, when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena.

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