UNRAVELING THE DECLINE IN HIGH-LATITUDE SURFACE OCEAN CARBONATE
Description: For perhaps 25 million years, surface waters throughout the ocean have
remained saturated with respect to calcium carbonate (CaCO3). Yet increasing atmospheric CO2
reduces ocean pH and carbonate ion concentration [CO32-] and thus the level of saturation. Despite this acidification, it has been
estimated that all surface waters will remain saturated for centuries. However,
marine calcifiers are still expected to suffer reductions in the rate at which
they form their exoskeletons out of CaCO3. Here we show with ocean
data and models that the anthropogenic acidification will actually cause some
surface waters to become undersaturated within decades, thus exacerbating the
problem for marine calcifiers [Orr et al.,
2005]. For instance, by 2050 when atmospheric CO2 reaches 550 ppmv
under the IS92a business-as-usual scenario, Southern Ocean surface waters begin
to become undersaturated with respect to aragonite, a metastable form of CaCO3.
By 2100 as atmospheric CO2 reaches 788 ppmv under the same scenario,
undersaturation extends throughout the entire Southern Ocean (all ocean south
of 60°S) and into the surbarctic Pacific.
Author's Names: J. C. Orr, V. J. Fabry, O. Aumont, L. Bopp, et al
Filesize: 92.06 Kb
Added on: 03-Aug-2005 Downloads: 142
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THE ROLE OF WATER RELATIONS IN DRIVING GRASSLAND ECOSYSTEM RESPONSES TO RISING ATMOSPHERIC CO2
Description:
While
rising atmospheric carbon dioxide (CO2) is known to be an important
contributor to radiative forcing of Earth’s climate, more direct effects of
this gas on photosynthesis and plant water relations have been underway for
more than a century, and likely have already contributed to important ecosystem
changes. Experiments conducted in native and semi-natural grasslands in which ambient
CO2 concentrations have been artificially increased have shown that
increasing CO2 often increases photosynthesis, results in higher
soil and plant water content, and can enhance plant water use efficiency, the
ratio of plant biomass produced per unit water transpired back to the
atmosphere. While these responses may appear beneficial, there are long-term
responses of ecosystems to CO2 such as alterations in the cycling
and availability of critical plant nutrients like nitrogen (N) which are likely
to change over time and may significantly alter CO2-enhanced
production and forage quality. Herein we discuss these phenomena and speculate
on the implications and the importance for world grasslands.
Author's Names: J.A. Morgan, E. Pendall, A.R. Mosier,et al
Filesize: 31.72 Kb
Added on: 02-Aug-2005 Downloads: 122
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THE POTENTIAL OF UPPER OCEAN ALKALINITY CONTROLS FOR ATMOSPHERIC CARBON DIOXIDE CHANGES
Description:
Extreme
global model scenarios of complete preservation and degradation of biogenic
particulate CaCO3 (calcium carbonate) in open ocean waters which are
supersaturated with respect to CaCO3 were carried out. According to
these experiments, the theoretical potential of upper ocean alkalinity controls
for changing the atmospheric pCO2 (CO2 partial pressure)
amounts to several hundred μatm on time scales of several 104 years.
Up to a timescale of 103 years, however, the respective influence is
minor as compared to an expected anthropogenic increase of the atmospheric pCO2
in the order of 500-1000
μatm.
Author's Names: Christoph Heinze
Filesize: 80.15 Kb
Added on: 29-Jul-2005 Downloads: 162
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SUBSTRATE INDUCED GROWTH RESPONSE OF SOIL AND RHIZOSPHERE MICROBIAL COMMUNITIES UNDER ELEVATED CO2
Description: The
maximal specific growth rate of microorganisms from rhizospheres of Populus deltoides grown under normal CO2 concentration
in the atmosphere (400 ppm) was lower compared to the assessments made for
plots under elevated CO2 (800 and 1200 ppm). A similar conclusion
was made for microbial communities from soil under winter wheat and sugar beets
grown under 370 and 550 ppm CO2 in the atmosphere. Three to four
years fumigation of field plots with elevated CO2 has been shown to
result in the formation of rhizosphere microbial communities characterized by
faster specific growth rates as compared to microbial community under control
plants.
Author's Names: S.A. Blagodatsky, E.V. Blagodatskaya, T.-H. Anderson, et al
Filesize: 147.23 Kb
Added on: 26-Jul-2005 Downloads: 196
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NITROGEN REGULATION OF CARBON SEQUESTRATION IN TERRESTRIAL ECOSYSTEMS IN RESPONSE TO RISING ...
Description:
A highly controversial issue in global change
research is the regulation of terrestrial carbon (C) sequestration by soil
nitrogen (N) availability. The Third Assessment IPCC Report predicts rising atmospheric CO2
alone could stimulate terrestrial carbon (C) sequestration by 350 – 980 Pg (=1015
g) C in the 21st Century. Sequestering 350 – 980 Gt C in terrestrial
ecosystems requires 7.7 – 37.5 Pg (N) based on a stoichiochemical relationship
that approximately 0.005 g N is required for 1 g C stored in long-lived plant
biomass (i.e., wood) and 0.067 g N for 1 g C sequestered in soil organic matter
(SOM). Thus, to realistically predict
future C sequestration in terrestrial ecosystems, we have to understand how
closely C and N processes are coupled in response to rising Ca.
Author's Names: Yiqi Luo
Filesize: 24.39 Kb
Added on: 01-Aug-2005 Downloads: 158
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IMPACT OF ELEVATED CO2 ON THE FOOD PRODUCTION OF NEPAL
Description: The
three cereal crops rice, maize and wheat cover over 75% of the total food
production of Nepal.
All the three crops rice, maize and wheat showed increased yield with doubling
the CO2 level but also followed a declined tendency at the elevated
temperature. Among the three crops, maize was the most affected by the rise in
temperature although increased CO2 level could increase the crop
yield. The Terai plains and the hills of Nepal were more affected. The
mountains, on the other hand, showed a favorable tendency.
Author's Names: Kishore Sherchand
Filesize: 66.33 Kb
Added on: 04-Aug-2005 Downloads: 32
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IMPACT OF ELEVATED CO2 AND TEMPERATURE ON SOIL CARBON SEQUESTRATION POTENTIAL OF TWO CONTRASTING...
Description: Carbon sequestration in soils might offset part
of the increase of CO2 in the atmosphere. Two contrasting
subtropical grassland species, bahiagrass (BG), Paspalum notatum Flügge, and rhizoma perennial peanut (PP), Arachis glabrata Benth., a legume, were
grown at Gainesville, Florida, USA, in field soil plots in four temperature
zones (baseline-ambient, +1.5, +3.0, and +4.5 °C) in four temperature-gradient
greenhouses, two each at 360 and 700 ppm CO2. The soil had been in
continuous cultivation for more than 20 years before plant establishment. Samples
from the top 20 cm of each plot were collected before plant establishment and six
years later, after the study ended. Soil organic carbon (SOC) increases across
the six years were greater for BG than PP, 1.396 and 0.746 g/kg, respectively. Belowground
biomass was also greater for BG than PP. Mean SOC gains in BG plots at 700 and
360 ppm CO2 were 1.450 and 1.343 g/kg, respectively (no CO2
effect). Mean SOC increases in PP plots at 700 and 360 ppm CO2 were
0.949 g/kg and 0.544 g/kg, respectively (significant CO2 effect).
Overall, SOC increased only for the first temperature increment, and thereafter
declined. Soil organic nitrogen (SON) accumulation patterns were similar to SOC
increases. Mean annual SOC accumulation was 475 kg/ha per year, comparable with
other studies. We conclude that carbon can be accumulated in soils converted to
grassland species in humid, subtropical environments. The SOC accumulation will
be greatest for species that have greater belowground biomass accumulation.
Author's Names: L.H. Allen, Jr, S.L. Albrecht, K.J. Boote, J.M.G. Thomas, and K.W. Skirvin
Filesize: 29.38 Kb
Added on: 25-Jul-2005 Downloads: 36
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GROWTH AND PHOTOSYNTHETIC RESPONSE OF DECIDUOUS TREE SAPLINGS IN A FREE AIR CO2 ENRICHMENT SYSTEM
Description:
We
examined the photosynthetic and growth traits of two woody species (birch) that
are dominant in northern Japan
under elevated CO2 concentration ([CO2]), using a free
air CO2 enrichment (FACE) system. Our results suggest that it is necessary to consider not only leaf-level
photosynthesis but also the entire plant physiology when using photosynthesis
to evaluate the growth response of two birch saplings under elevated [CO2].
Author's Names: N. Eguchi, K. Karatsu, T. Ueda, R. Funada, et al
Filesize: 123.78 Kb
Added on: 28-Jul-2005 Downloads: 42
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FOREST MICROMETEOROLOGICAL RESPONSES TO INCREASED CO2 AND O3 CONCENTRATIONS
Description: The
Forest-Atmosphere Carbon Transfer and Storage (FACTS-II) Project in northern
Wisconsin is examining the interacting effects of elevated carbon dioxide (CO2)
and ozone (O3) concentrations on the productivity, sustainability,
and competitive interactions in a regenerating northern hardwood
ecosystem. A key component of this
project involves an examination of the micrometeorological feedback mechanisms
that can alter atmospheric environments within and above vegetation layers
exposed to elevated CO2 and O3 concentrations. This paper provides a brief summary of some
of the observed forest micrometeorological responses to elevated CO2
and O3 concentrations at the FACTS-II study site over the 1999-2004
period.
Author's Names: W.E. Heilman, and R.M. Teclaw
Filesize: 58.80 Kb
Added on: 29-Jul-2005 Downloads: 41
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FEEDBACKS BETWEEN CLIMATE AND THE ATMOSPHERE IN FOREST GROWTH: CLIMATIC VARIATION MEDIATES ...
Description: CO2 and O3 are accumulating in
the atmosphere and are potent modifiers of forest growth, causing changes that
could alter composition and functioning of forest ecosystems. We have examined the effects of elevated CO2
( +CO2; 560ppm), elevated O3 (+O3; 1.5X
ambient), and their combination (+CO2+O3),
on the growth and productivity of model aspen (Populus tremuloides Michx.) and aspen-birch (Betula papyrifera Marsh.) forest ecosystems growing in an open
free-air exposure (FACE) system in northern Wisconsin USA. After eight years of fumigation, +CO2
increased aspen tree and stand volume growth by 39 + 9% and 38 +
10%, respectively, whereas +O3 decreased them by 27 + 6% and
34 + 4%, respectively. +CO2+O3 resulted in a net
canceling of the effects of the single gases on aspen growth. Forest
growth responses to +CO2 and +O3 interacted strongly with
present-day interannual variability in climatic conditions. The amount and
timing of photosynthetically active radiation and temperature coinciding with
growth phenology explained 33-61% of the annual variation in growth responses
of aspen trees, and explained 20-63% of annual variation in growth responses of
aspen tree stands.
Author's Names: M.E. Kubiske, V.S. Quinn, W.E. Heilman, et al
Filesize: 73.21 Kb
Added on: 03-Aug-2005 Downloads: 43
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