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 11, NUMBER 10, OCTOBER 1998
ELEVATED-CO2 EFFECTS ON PLANTS
Interactions of CO2 Enrichment and Temperature on Cotton
Growth and Leaf Characteristics, K. R. Reddy (Dept. Plant and Soil
Sci., Miss. State Univ., Box 9555, Mississippi State, MS, 39762) et al.,
Env. Exptl. Bot. 39 (27), 117-129 (1998).
The stomatal density and index of upland cotton were not affected by the
elevation of atmospheric CO2 concentration. Leaves were larger
in area and had higher biomass under elevated CO2 at all
temperatures. The optimum temperature for vegetative and reproductive
growth was not changed by CO2 concentration. Flower and fruit
retentions were severely curtailed by higher temperatures but unaffected
by CO2 concentration, underscoring the need to use species and
cultivars that are heat resistant in warmer climates.
The Effect of Elevated CO2 Concentration and Nutrient
Supply on Carbon-Based Plant Secondary Metabolites in Pinus sylvestris
L., C. J. Heyworth (MLURI, Craigiebuckler, Aberdeen AB15 6QH,
Scotland), et al., Oecologia 115, 344-350 (1998).
Elevated CO2 increased dry mass per needle, tree height, and
monoterpene a-pinene concentration, and the cellulase digestibility of the
needles was increased by the high nutrient availability. But, expected
increases in atmospheric CO2 will not be great enough to
change the concentrations of tannins and monoterpenes in Scots pine nor
influence the secondary processes like decomposition and herbivore food
Photosynthetic Pathway and Ontogeny Affect Water Relations and the
Impact of CO2 on Bouteloua gracilis (C4) and Pascopyrum
smithii (C3), J. A. Morgan (USDA/ARS, 1701 Centre Ave., Ft.
Collins, CO, 80526; firstname.lastname@example.org) et al., Oecologia
114, 483-493 (1998).
In growth-chamber studies, both species exhibited increases in leaf CO2
assimilation, photosynthesis, transpiration use efficiency, plant growth,
and water-use efficiency with elevated CO2. Effects were more
pronounced in the Pascopyrum. Decreased soil-water content was
associated with increased sequestering of carbohydrates and the production
of more belowground biomass in the Pascopyrum. It also exhibited
increased root-to-shoot ratios at elevated CO2.
Effects of Climate and Atmospheric CO2 Partial Pressure
on the Global Distribution of C4 Grasses: Present, Past, and Future,
G. J. Collatz (Goddard Space Flight Center, Code 923, Greenbelt, MD,
20771; email@example.com), J. A. Berry, J. S. Clark, Oecologia
114, 441-454 (1998).
Maps were constructed from climatological data sets to classify the
globe into areas that favor grasses that use the C4 photosynthetic pathway
and thus to model plant-community responses to atmospheric CO2
concentration. Lowering the CO2 concentration to preindustrial
levels expanded the range of C4 grasses. Conditions during the most recent
glacial maximum substantially favored C4 vegetation. Doubling the current
CO2 concentration substantially reduces todays area of
The Effects of Parental CO2 Environment on Seed Quality
and Subsequent Seedling Performance in Bromus rubens, T. E.
Huxman (Dept. Biol. Sci., Univ. Nev. Las Vegas, Las Vegas, NV, 89154;
firstname.lastname@example.org) et al., Oecologia 114, 202-208
Seeds of an exotic annual grass grown under elevated CO2 had
larger pericarp surface areas, higher C:N ratios, and less mass than
normal seeds of the species, but their germination ratio and germination
time were unchanged. The elevated-CO2 seeds had smaller seed
reserves, exhibited a reduced growth rate, and attained smaller final
mass. The higher C:N ratios may severely affect seed quality and seedling
A Meta-Analysis of Elevated CO2 Effects on Woody Plant
Mass, Form, and Physiology, P. S. Curtis (Dept. Plant Biol, The Ohio
Stat Univ., 1735 Neil Ave., Columbus, OH, 43210; email@example.com),
Xianzhong Wang, Oecologia 113, 299-313 (1998).
An integration of the literature on the effects of elevated CO2
on woody plants indicates that total biomass and net CO2
assimilation increase significantly at doubled CO2, regardless
of growing conditions. Low soil-nutrient availability reduces the CO2-fertilization
effect, low light increases it, and interacting stress factors do not
affect it. No significant shifts are seen in biomass allocation, in
stomatal conductance, or in photosynthesis (i.e., no acclimation to the
elevated CO2 occurs). Dark respiration and leaf nitrogen both
increase with CO2 enrichment, and leaf starch content
Long-Term Responsiveness to Free Air CO2 Enrich-ment of
Functional Types, Species, and Genotypes of Plants from Fertile Permanent
Grassland, A Lüscher (Inst. Plant Sci., Swiss Fed. Inst.
technol., CH-8092 Zurich, Switzerland; firstname.lastname@example.org),
G. R. Hendrey, J. Nösberger, Oecologia 113, 37-45
Among grasses, nonleguminous dicots, and legumes, legumes showed the
strongest yield increase in response to elevated CO2 and
grasses the weakest. Legume response declined from the first to second
year, while nonleguminous- dicot response increased for three years. The
grasses and nonleguminous dicots exhibited the strongest response during
reproductive growth in the spring. No genotypic differences were observed
in response to elevated CO2. The interspecies differences in
temporal distribution of the effects imply that elevated CO2
would produce complex competitive interactions in mixed communities of
Nutrient Relations in Calcareous Grassland Under Elevated CO2,
P. A. Nicklaus (Inst. Botany, Schönbeinstrasse 6, CH-4056 Basel,
Switzerland; email@example.com) et al., Oecologia 116,
In calcareous grasslands, total biomass nitrogen, total aboveground
phosphorus, and tissue N:P ratios were not altered by CO2
enrichment. In legumes, the C:N ratio was not altered, but the N:P ratio
was increased slightly. Although total-plant nitrogen was not affected by
elevated CO2, microbial nitrogen pools increased, and
plant-available soil nitrogen decreased. Greenhouse experiments also
indicated that plant nitrogen pools were unaffected by elevated CO2;
however, when phosphorus was added along with CO2 enrichment,
total-plant nitrogen pools increased, suggesting a complex interaction
among CO2 concentration, nitrogen availability, and phosphorus
Effects of Elevated CO2 and Phosphorus Addition on
Productivity and Community Composition of Intact Monoliths from Calcareous
Grassland, Jürg Stöcklin (Inst. Bot., Univ. Basel, Schönbeinstrasse
6, CH-4056 Basel, Switzerland; firstname.lastname@example.org), Kathrin Schweizer,
Christian Körner, Oecologia 116, 50-56 (1998).
When calcareous grassland was exposed to elevated CO2 in a
greenhouse, aboveground dry mass remained unchanged during the first year
but increased significantly in the second year. Belowground biomass was
unchanged by the elevated CO2. The effect on biomass of
phosphorus alone was small. Some species (e.g., Bromus erectus)
responded negatively to elevated CO2, and during the second
year, the community composition shifted towards species that were more
responsive to elevated CO2. Biomass production at elevated CO2
was higher when phosphorus was added. These results indicate that
interactions among CO2 concentration, species selection, and
nutrient availabilities govern plant-community responses to elevated CO2.
Effect of Enhanced Atmospheric CO2 on Mycorrhizal
Colonization by Glomus mosseae in Plantago lanceolata and
Trifolium repens, P. L. Staddon (Dept. Biol., Univ. York,
P.O. Box 373, York, YO1 5YW, U.K.; email@example.com), J. D. Graves, A. H.
Fitter, New Phytol. 139, 571-580 (1998).
Both species grew faster in elevated CO2. Elevated CO2
did not affect the percentage of root length colonized, colonization
intensity, or phosphorus inflow, and it did not have any direct permanent
effect on mycorrhizal functioning.
Effects of a Natural Source of Very High CO2
Concentration on the Leaf Gas Exchange, Xylem Water Potential, and
Stomatal Characteristics of Plants of Spatiphylum cannifolium and
Bauhinia multinervia, M. D. Fernández (Cent. Bot.
Trop., Inst. Biol. Exptl., Univ. Cent. Venezuela, Apartado 47577, Caracas
1041A, Venezuela; firstname.lastname@example.org) et al., New Phytol.
138, 689-697 (1998).
Xylem water potential was lowered by drought, and elevated CO2
lowered it further in the Spatiphylum. Plants growing under
elevated CO2 had higher photosynthetic rates, increased
water-use efficiency, and depressed stomatal initiation. These factors
combined to allow the elevated-CO2 plants to attain higher
Elevated CO2 and Tree Root Growth: Contrasting Responses
in Fraxinus excelsior, Quercus petraea, and Pinus
sylvestris, Meg Crookshanks (Sch. Biol. Sci., Univ. Sussex,
Falmer, Brighton, Sussex, BN1 9QG, U.K.; email@example.com), Gail
Taylor, Mark Broadmeadow, New Phytol. 138, 241-250 (1998).
Elevated CO2 significantly increased root growth, with the
greatest increase occurring in ash and the smallest in oak. Changes in
specific root length suggest that root diameter and/or density were
increased. Root dry weight, later root numbers, and mean root diameter
were increased in all species. Root respiration rates were significantly
reduced in all three. Soluble sugars increased significantly in all
species but starch content increased in some and decreased in others.
Elevated Carbon Dioxide Ameliorates the Effects of Ozone on
Photosynthesis and Growth: Species Respond Similarly Regardless of
Photosynthetic Pathway or Plant Functional Group, J. C. Volin (Dept.
Forestry, Univ. Wisc., 1630 Linden Dr., Madison, WI, 53706;
firstname.lastname@example.org), P. B. Reich, T. J. Givnish,New Phytol. 138
(2), 241-250 (1998).
Elevated CO2 had little effect on the photosynthesis and
relative growth rate of two C3 trees, two C3 grasses, and two C4 grasses.
High ozone levels depressed photosynthesis, relative growth rate, and root
weight ratio in almost all cases, but these effects were not seen when
both CO2 and ozone levels were elevated.
High-stomatal-conductance species were the most susceptible to oxidant
damage. Elevated CO2 reduces stomatal conductance and might,
therefore, reduce the damage caused by oxidants.
Effects of Nitrogen and Water Limitation and Elevated Atmospheric CO2
on Ectomycorrhiza of Longleaf Pine, G. B. Runion (Sch. Forestry, 108
M. White Smith Hall, Auburn Univ., AL, 36849; email@example.com)
et al., New Phytol. 137, 681-689 (1998).
Seedlings grown in elevated CO2, low nitrogen, and adequate
water had almost double the normal numbers of ectomycorrhizal short roots
and ectomycorrhizas, but these results occurred only when the nitrogen
concentration was elevated.
Nitrogen Balance for Wheat Canopies (Triticum aestivum cv.
Veery 10) Grown Under Elevated and Ambient CO2 Concentrations,
D. R. Smart (Dept. Veg. Crops, Univ. Calif., 1 Shields Ave., Davis, CA,
95616; firstname.lastname@example.org) et al., Plant Cell Env. 21,
Wheat plants grown under elevated CO2 increased carbon
allocation to root biomass production and root-zone nitrate consumption
but not biomass nitrogen content. Instead, nitrogen loss increased. This
diminished nitrate assimilation explains why organic nitrogen contents of
plants decline in elevated CO2.
The Stomatal Response to CO2 Is Linked to Changes in
Guard Cell Zeaxanthin, J. Zhu (Dept. Biol., Univ. Calif., Los
Angeles, CA, 90095; email@example.com) et al., Plant Cell Env.
21, 813-820 (1998).
Elevated CO2 decreased zeaxanthin content in leaves and
decreased stomatal apertures under lighted conditions. In the dark,
however, the changes in stomatal aperture caused by elevated CO2
were much smaller, and the concentration of guard-cell zeaxanthin did not
change. These results indicate that CO2-produced changes in
zeaxanthin content modulate stomatal responses to CO2 in the
light while another mechanism modulates CO2 response in the
Response of Sugar Beet (Beta vulgaris L.) Yield and
Biochemical Composition to Elevated CO2 and Temperature at Two
Nitrogen Applications, H. Demmers-Derks (Biochem. Physiol. Dept.,
IACR-Rothamsted, Harpenden, Hertfordshire, AL5 2JQ, U.K.) et al., Plant
Cell Env. 21, 829-836 (1998).
Elevated CO2 increased total dry mass at harvest by 21%
under high-nitrogen and 11% under low-nitrogen conditions. The respective
increases in root dry mass were 26% and 12%. Warmer temperatures, however,
decreased both total and root dry masses. Neither elevated CO2
or temperature influenced root sucrose concentration. Amino acids
decreased in elevated CO2 and increased in warmer
Tansley Review No. 98: Tree and Forest Functioning in an Enriched CO2
Atmosphere, Henrik Saxe (Inst. Bot., Dendrol., Forest Gen., The
Arboretum The Royal Vet. and Ag. Univ., Kirkegaardsvej 3A, DK-2970,
Hoersholm, Denmark; firstname.lastname@example.org), D. S. Ellsworth, James Heath, New
Phytol. 139 (3), 395-436 (1998).
A review of the literature reveals a significantly larger long-term
increase in biomass for conifers than for deciduous trees under elevated
CO2, although stimulation of photosynthesis was similar and
larger than previously believed. The many down-regulation pathways make
predicting growth and canopy CO2 exchange uncertain, and the
down-regulation of photosynthesis is rarely large enough to offset the
photosynthetic gains. The response of stomatal conductance to elevated CO2
in trees is very different from that in herbaceous species. Canopy
transpiration is affected positively by changes in leaf area and
negatively by changes in stomatal aperture. Elevated CO2 can
alter tree-soil interactions and, thus, ecosystem productivity. Moreover,
changes in foliage carbon, mineral nutrients, and secondary metabolites
brought about by elevated CO2 can influence tree-insect
interactions. In most trees, mycorrhizal interactions are affected more by
nutrient deficiencies than they are by CO2 concentration.
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