February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 8, NUMBER 11, NOVEMBER 1995
IMPACTS OF ELEVATED CO2
"Towards a Better Experimental Basis for Upscaling Plant Responses
to Elevated CO2 and Climate Warming," Ch. Körner (Inst. Botany, Univ.
Basel, CH-4056 Basel, Switz.), Plant, Cell & Environ., 18(10),
1101-1110, Oct. 1995.
Few of the most common assumptions used in modeling plant and ecosystem
responses to elevated CO2 and temperatures have been tested under realistic life
conditions. Identifies unexpected discrepancies between predictions and
experimental findings, which indicate that a better empirical basis is required
for predictions. Offers ten suggestions for improving our ability to scale up
from experimental conditions to the real world.
"Stomatal Responses to Increased CO2: Implications from the Plant to
the Global Scale," C.B. Field (Carnegie Inst. of Washington, Stanford CA
94305), R.B. Jackson, H.A. Mooney, ibid., 1214-1225.
There are few studies of ecosystem effects of elevated CO2 mediated through
decreased leaf conductance of moisture. This discussion is based on theory,
experiments in which other variables provide surrogates for CO2 effects, and a "healthy
dose of speculation." Concludes that, because certain negative feedbacks
depend on the aerodynamic roughness of the terrain, effects of elevated CO2 on
conductance are unlikely to have large effects on the hydrological cycle in
productive (aerodynamically smooth) agricultural regions, but will be most
important in natural forests, shrublands and dry grasslands. Decreased canopy
conductances over large regions may lead to increased temperature and decreased
precipitation, and these climatic effects could be important regionally,
especially in combination with greenhouse warming.
"Elevated Concentrations of CO2 May Double Methane Emissions from
Mires," P.R. Hutchin, M.C. Press (Dept. Animal & Plant Sci., Univ.
Sheffield, POB 601, Sheffield, UK) et al., Global Change Biology, 1(2),
125-128, Apr. 1995.
Intact cores of peat and vegetation were removed from a mire and buried in
open top chambers, where they were exposed to a 60% increase in CO2. A profound
increase in methane emissions was observed over the four-month period of study,
accompanied by a 100% increase in the rate of photosynthesis.
"Effects of Elevated CO2 and/or O3 on Growth, Development and
Physiology of Wheat (Triticum aestivum L.)," J.D. Barnes (Dept.
Agric. Sci., Univ. of Newcastle-upon-Tyne, Newcastle-upon-Tyne NE1 7RU, UK),
J.H. Ollerenshaw, C.P. Whitfield, ibid., 129-142.
Plants exposed to both ozone and CO2 in a test chamber showed enhanced
growth due to elevated CO2, but little evidence that CO2 enrichment afforded
extra protection against O3 damage. On the contrary, CO2 enrichment may render
plants more susceptible to O3 damage at the cellular level.
"Elevated Carbon Dioxide Affects Leaf-Miner Performance and Plant
Growth in Docks (Rumex spp.)," D.T. Salt (Biolog. Sciences,
Lancaster Univ., Lancaster LA1 4YQ, UK), G.L. Brooks, J.B. Whittaker, ibid.,
Plants exposed to elevated CO2 showed greater leaf area and an increased C:N
ratio, but leaf miners also produced larger mines in the leaves. Results are
consistent with the hypothesis that herbivores compensate for increased C:N
ratios by increased food consumption, an effect which could partially offset
predicted increases in plant biomass in a future high-CO2 environment.
"Modelling the Effects of Atmospheric CO2 on Vegetation-Atmosphere
Interactions," A.D. Friend (Inst. Terr. Ecol., Bush Estate, Penicuik EH16
0QB, UK), P.M. Cox, Agric. & Forest Meteor., 73(3-4),
285-295, Mar. 1995.
Describes experiments with a combined climate-vegetation model simulating
doubled CO2 at an Amazon location. Results show that vegetation and climate
responses to CO2 concentration cannot be considered in isolation: the effects of
feedback could be at least as important as any direct effects.
"Tansley Review No. 71: Effects of Elevated Atmospheric CO2 on Woody
Plants," R. Ceulemans (Dept. Biol., Univ. Antwerpen, UIA,
Universiteitsplein 1, Wilrijk B-2610, Belg.), M. Mousseau, New Phytologist,
127(3), 425-446, July 1994.
A major review of experimental methods and findings, emphasizing changes in
underground processes and how they relate to the functioning of the ecosystem.
Discusses directions for future research.
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Index of Abbreviations