LINKS BETWEEN GLOBAL CO2 VARIABILITY AND CLIMATE ANOMALIES OF BIOMES
Description:
The
global rate of fossil fuel combustion continues to rise, but the amount of CO2
accumulating in the atmosphere has not increased accordingly (Tans et al., 1990; Conway et al., 1994; Wofsy,
2001). The causes for this discrepancy
are widely debated (Houghton,
2003). In particular, the location and
drivers for the interannual variability of atmospheric CO2 are
highly uncertain. Here we examine links
between global atmospheric CO2 growth rate (CGR) and the climate anomalies
of biomes based on ten years (1986-1995) of global climate data and
accompanying satellite data sets. Our
results show that four biomes, the tropical rainforest, tropical savanna, C4
grassland and boreal forest, and their responses to climate anomalies, are the
major climate-sensitive CO2 sinks/sources that control the CGR. The nature and magnitude by which these
biomes respond to climate anomalies are generally not the same. However, one common influence did emerge from
our analysis; the extremely high CGR that was observed for the one extreme El
Niño year was caused by the response of the tropical biomes (rainforest,
savanna and C4 grassland) to temperature.
Author's Names: C. Yi, T. Zhou, P. S. Bakwin, L. Zhu and R. K. Monson
Filesize: 43.61 Kb
Added on: 09-Aug-2005 Downloads: 29
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LONG TERM TEMPORAL AND SPATIAL VARIABILITY OF CARBON IN PERMAFROST–DOMINATED FOREST ECOSYSTEMS
Description:
The forests of Siberia
represent one of the last natural frontiers in the world. Nearly 65% of
Siberia's forests grow in areas with permafrost and Larch
forests are dominated here. According to our estimates, carbon stocks
in the
soils of permafrost forest and tundra ecosystems of Yakutia amount to
17 Gt
(altogether 126 Mha of forest area and 37 Mha of tundra). It is
about 25% of total carbon stock in
forest soils of the Russian Federation. This carbon has been
accumulated
during centuries, and rapid climate change may release its huge amount
for
relatively short period, thus enhancing rather source than sink role of
Russia.
The total stock of terrestrial phytomass carbon of forests, tundra and
meadows
of Yakutia is 2.2-4.5 Gt C, including 0.053 Gt C of tundra and meadows.
Author's Names: T.C. Maximov, A.J.Dolman, M.K.van der Molen, et al
Filesize: 84.13 Kb
Added on: 02-Aug-2005 Downloads: 24
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LONG-TERM OBSERVATION OF CO2 FLUX ABOVE A BROADLEAVED DECIDUOUS FOREST IN SAPPORO, NORTHERN JAPAN
Description:
A long-term observation of CO2 exchange was
conducted above a broadleaved deciduous forest in Sapporo,
northern Japan.
The CO2 exchange was measured using the eddy covariance method with
closed-path gas analyzer and we obtained net ecosystem production (NEP). We estimated a carbon budget using a simple
empirical model. In this model, ecosystem respiration (RE) and gross primary
production (GPP) were parameterized by soil temperature and photosynthetically
active radiation (PAR)
respectively. The annual NEP
derived from an equation “NEP = GPP
-RE” ranged from 237 to 431 g C m-2
year-1 for 4 years (2000 - 2003).
Author's Names: K. Kitamura, Y. Nakai, S. Suzuki, K. Yamanoi, et al
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Added on: 01-Aug-2005 Downloads: 22
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MAPPING NPP AND BIOMASS IN WEST SIBERIAN WETLANDS
Description:
The objective of this study is to provide
improved estimation of the area extent for major mire types within West Siberia
(WS) and determine the spatial variability of NPP and biomass in relation to
macro/micro landscape and site position within the bioclimatic division. Our
approach relies upon scaling up available field survey and literature data to
provide wetland net primary production (NPP) and biomass inventory maps for West Siberia. Both, satellite images and aerial
photography classifications have been used to extrapolate site data into a regional
inventory map (1:2.5M scale). Total NPP of wetlands is estimated as 530.5 TgDM
(teragram/megaton dry matter)yr-1, or 624.4 TgDM/yr when woody parts are
included. Lowest NPP has been assigned to wetlands at the northern part of
Taiga zone (4.5-6.2 tonDM)/ha/yr-1). Wetlands in Tundra, Forested
tundra and southern parts of Taiga zone show considerably higher NPP values.
Minimum of living biomass storage was found in middle and southern taiga
subzones. It is also increased to the north and south within West Siberian
territory.
Author's Names: A. Peregon, S. Maksyutov, N. Kosykh, et al
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Added on: 03-Aug-2005 Downloads: 28
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MEASUREMENTS OF CO2 FLUXES OVER TWO DIFFERENT UNDERLYING SURFACES IN AN AGRICULTURAL LANDSCAPE ...
Description: In order to better
understand the regional climate change, it is necessary to quantify the CO2
flux over agricultural landscapes. CO2 fluxes were collected
directly by using eddy covariance over two different underlying surfaces (i.e.,
a rice paddy, and a mixed crop surface) in an agricultural landscape in the
central China
over two periods of 40 days in 2001 and 2002 respectively, in which significant
plant growth occurred. Results show (1) that daytime absorption of CO2
flux by the rice paddy gradually increased but nighttime release of CO2
flux by the rice paddy did not; (2) that, for both rice paddy and mixed crop
surface, daytime absorption of CO2 significantly increased after
rain events, but nighttime release of CO2 almost did not change; and
(3) that maximum diurnally daytime absorption of CO2 reached 6 g m-2
h-1 over rice paddy and 2.8 g m-2 h-1
over the mixed crop surface respectively
Author's Names: Z. Gao, and L.Bian
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Added on: 28-Jul-2005 Downloads: 22
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MODELING DAILY AND SEASONAL DYNAMICS OF CO2 STABLE CARBON ISOTOPIC EXCHANGE BETWEEN BOREAL ...
Description:
In
this study, we developed an integrated modeling system to simulate dynamics of a
stable carbon isotope of CO2, moisture, energy, and momentum between
boreal ecosystems and the atmosphere as well as their diffusion processes
through the whole convective boundary layer (CBL), using remotely sensed
surface parameters to characterize the surface heterogeneity, and the marine
boundary layer matrix data to represent the CBL top condition. Model validation
and primary results in boreal ecosystems were presented in this paper.
Author's Names: B. Chen, J. M. Chen, L. Huang, and P. Tans
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Added on: 05-Aug-2005 Downloads: 24
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MODELING NET ECOSYSTEM PRODUCTIVITY: SCALE ISSUES AND REGIONAL APPLICATION TO THE IBERIAN PENINSULA
Description:
Our research goal is to assess the regional vegetation
dynamics in the Iberian Peninsula (IP). For this purpose, estimations of net
ecosystem production (NEP) from a
productivity ecosystem model, the Carnegie Ames Stanford Approach (CASA) model [Potter
et al., 1993], were compared with
local CO2 flux measurements. The CASA
calibration process aimed the tuning of efficiency scalars directly related to
net primary productivity and soil respiration calculations: maximum light use
efficiency (ε*) and temperature
effect on soil fluxes (Q10),
respectively. Local weather station data was used for climatic inputs, as well
as remotely sensed leaf area index (LAI) and fraction of photosynthetically
active radiation (FPAR) from the MODIS TERRA sensor. Firstly, NEP calculations were performed at different temporal
resolutions, ranging from monthly to daily time steps, in order to assess the
impact of temporal scales on productivity estimates. Both the calibration and
validation procedures showed significant confidence, although the main
processes behind vegetation carbon fluxes were best simulated at temporal scales
ranging from 8 days to monthly. The impact of spatial scale was also analyzed
on the NEP estimates. It was found
that results accuracy was influenced by the data spatial resolution, and,
furthermore, by the tree cover percentage of the aggregated cells. A correction
method was implemented and a reduction of the spatial aggregation error up to
10% was obtained. The long term NEP
analysis for the IP indicates statistically significant positive trends mainly
related to solar radiation positive trends. A less significant negative trend
was also found with a strong spatial autocorrelation behavior.
Author's Names: N. Carvalhais, J. Seixas and R. Myneni
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Added on: 28-Jul-2005 Downloads: 47
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MODELING TERRESTRIAL CO2 SOURCES, SINKS, AND ATMOSPHERIC TRANSPORT USING ASSIMILATED ...
Description:
Progress
in determining CO2 sources, sinks, and their response to
environmental forcing will rely on utilization of more extensive and intensive
CO2 and related observations including those from satellite remote
sensing. Full exploitation of new
observations will require new modeling and analysis techniques, especially
those that can use information at finer spatial and temporal scales than has
traditionally been employed in “top-down” carbon flux studies. We report on a modeling effort to reduce
uncertainty in carbon cycle processes that create the so-called missing
terrestrial sink of atmospheric CO2 using transport fields derived
from NASA’s GEOS-4 meteorological assimilation analyses. Our overall objective is to improve
characterization of CO2 source/sink processes globally with improved
formulations for atmospheric transport, terrestrial uptake and release, biomass
and fossil fuel burning, and observational data analysis. We show results from an advanced biosphere
model (SiB3) constrained by remote sensing data and coupled to the global
transport model to produce distributions of CO2 fluxes and
concentrations that are consistent with actual meteorological variability. Use of analyzed meteorological data allows
comparison to observations on a wide range of temporal and spatial scales. Here we compare with local-to-global data for
hourly to annual CO2 simulation.
The results will help to prepare for the use of satellite CO2
and other data in a multi-disciplinary carbon data assimilation system for
analysis and prediction of carbon cycle changes and carbon/climate
interactions.
Author's Names: S.R. Kawa, A.S. Denning, S.L. Conner-Gausepohl, et al
Filesize: 104.98 Kb
Added on: 01-Aug-2005 Downloads: 32
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MODELING THE HISTORY OF TERRESTRIAL CARBON SOURCES AND SINKS
Description: We
report modeling experiments with a new global dynamic land model (LM3V), to
reconstruct possible causes of the terrestrial carbon sources and sinks over
the past century. The model is unique,
in that it is capable of representing the global history of land use, including
the management of secondary forests (those forests that have re-grown at least
once following harvest). Several published carbon inventories attribute the
majority of the carbon sink caused by land use in the temperate zone to the
management of secondary forests.
Author's Names: S.W. Pacala, G.C. Hurtt, E. Shevliakova, and S. Malyshev
Filesize: 17.72 Kb
Added on: 03-Aug-2005 Downloads: 127
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MONITORING EFFECTS OF INTERANNUAL VARIATION IN CLIMATE AND FIRE REGIME ON REGIONAL NET ...
Description: A
spatially-distributed model of net ecosystem production (NEP) was run over western Oregon for the period 2001-2003 at the 1 km
spatial resolution and daily temporal resolution. Inputs included MODIS-based FPAR, Landsat-based
land cover and disturbance history, and distributed meteorology. Resulting NEP showed sensitivity to 1) areas of recent
disturbance, such as a large forest fire in 2002, 2) areas of intensive
management for timber production, 3) topographically-driven climatic gradients,
and 4) interannual variation in climate. Validation measurements included a
network of field plots and a chronosequence study.
Author's Names: D.P. Turner, W.D. Ritts, J. Styles, Z. Yang, et al
Filesize: 20.65 Kb
Added on: 08-Aug-2005 Downloads: 113
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