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
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Added on: 02-Aug-2005 Downloads: 122
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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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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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CALCITE AND ARAGONITE UNDERSATURATION UNDER RISING ATMOSPHERIC CARBON DIOXIDE CONCENTRATIONS ...
Description:
Increasing atmospheric CO2
concentrations lowers oceanic pH and carbonate ion concentrations, thereby
decreasing the level of saturation of calcium carbonate [Feely et
al., 2004]. This acidification will eventually lead to
undersaturation and dissolution of calcium carbonate in parts of the surface
ocean. Besides affecting the global carbon cycle, these changes threaten marine
organisms that form their exoskeletons out of CaCO3, which are
essential components of the marine food web [Orr et al.,
2005]. We investigate magnitude and pattern of ocean acidification due to
increasing atmospheric CO2 concentrations and global warming, both
for the recent past and the near future, using the reduced complexity, Bern 2.5-D
physical-biogeochemical climate model and a series of CO2 emission
scenarios and CO2 stabilization profiles provided by the
Intergovernmental Panel on Climate Change (IPCC). The focus of the study is on
the impact of global warming and induced ocean circulation changes on the
projected oceanic pH and carbonate ion reductions.
Author's Names: G.-K. Plattner, F. Joos, T. Stocker, and J. C. Orr
Filesize: 24.71 Kb
Added on: 03-Aug-2005 Downloads: 53
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EFFECT OF ENRICHED CO2 ON RICE UNDER OPEN TOP CHAMBER CONDITION AT KHUMALTAR
Description:
The effect of CO2
enrichment in raising the temperature was realized in the Open Top Chamber
(OTC) experiment. The elevated CO2 with this level of temperature
raised grain yield and yield components of rice but varied greatly by year. The
CO2 enriched plot had lesser N, P, and K in grain, straw, and root
but higher organic carbon (OC) in the root compared to the Ambient and the
Field. The study indicated that this rise of temperature due to the elevated CO2
could not adversely affect the yield.
Author's Names: K. Sherchand, G. Malla, A. Sharma and S. Shrestha
Filesize: 53.20 Kb
Added on: 04-Aug-2005 Downloads: 64
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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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EFFECT OF ELEVATED CO2 ON GROWTH, BIOMASS PRODUCTION AND PHOTOSYNTHESIS OF PANICUM MAXIMUM AND ...
Description:
In P. maximum the
cumulative dry biomass production in two cuttings showed an increase of 59.24%
and 43.17% in open top chambers (OTC) with elevated CO2 (600±50
ppm) (C600) and without elevated CO2 (COTC)
respectively over the open field grown corps (Ca). In S. hamata the dry matter increased by
39.79% under C600 and 31.02% in COTC over Ca. The canopy
photosynthesis (PN x LAI) increased significantly in both the crop
species with elevated CO2. The increased rate of canopy
photosynthesis indicated that there was higher assimilation of CO2,
which has intern maximum biomass production. The increase in fresh and dry
matter accumulation in C600 indicating that these crop species
should be promoted for higher biomass production and carbon sequestration in
the semi arid tropical environmental conditions.
Author's Names: R. K. Bhatt, M.J. Baig, Jyoti Dubey and H. S. Tiwari
Filesize: 90.35 Kb
Added on: 05-Aug-2005 Downloads: 64
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BAYSIAN INVERSION OF A TERRESTRIAL ECOSYSTEM MODEL AND UNCERTAINTY ANALYSIS
Description:
We applied the Bayesian
probability inversion and a Markov Chain Monte Carlo (MCMC)
technique to a terrestrial ecosystem model and analyzed uncertainties of
estimated carbon transfer coefficients and simulated carbon pool sizes. The
study used six data sets of soil respiration, woody biomass, foliage biomass,
litterfall, carbon content in the litter layers, carbon content in mineral soil
measured under both ambient CO2 (350 ppm) and elevated CO2
(550 ppm) plots from 1996 to 2000 at the Duke Forest Free-Air CO2
Experiment (FACE) site.
Author's Names: Tao Xu, Yiqi Luo
Filesize: 244.22 Kb
Added on: 09-Aug-2005 Downloads: 45
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A PAEO PERSPECTIVE ON THE OCEAN'S ROLE IN THE CARBON CYCLE
Description: Recently developed proxies for the seawater carbonate ion concentration
were used to reconstruct the vertical gradient in the carbonate ion
concentration for times in the past corresponding to the
glacial-interglacial cycles. The reconstructed changes leave little
doubt that the ocean drove the large natural variations in atmospheric
carbon dioxide that accompanied the glacial cycles, most likely through
the combined influence of changes in the biological pump and deep ocean
circulation. Below 1500 m the carbonate ion concentration changes
little, evidence of the ocean’s ability to buffer changes in carbon
chemistry over thousands of years.
Author's Names: David M. Anderson
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Added on: 26-Aug-2005 Downloads: 59
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