EFFECTS OF DISTURBANCE AND CLIMATE CHANGE ON CARBON BALANCE IN CANADA’S FORESTS AND WETLANDS
Description:
Model
simulations indicated that Canada’s
forests and wetlands acted as a carbon (C) sink of 112 Tg C
yr-1 averaged during 1901-1998. Wetlands was a crucial contributor
to this sink (50 Tg C yr-1). Disturbance history determined the decadal temporal pattern of C
balance. Nondisturbance factors enhanced C accumulations in Canada’s forests and
wetlands in the last century. The enhancement of each nondisturbance factor on
C uptake changed temporally.
Author's Names: W. Ju, and J. M. Chen
Filesize: 84.65 Kb
Added on: 29-Jul-2005 Downloads: 18
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ESTIMATING AND EVALUATING TERRESTRIAL CARBON FLUXES USING A BIOSPHERE MODEL IN TOKAI REGION
Description: Terrestrial carbon
fluxes are an important factor for the studies of global warming. This study
focuses on estimating a fluctuation
of the terrestrial carbon fluxes in the
Tokai region, Japan.
The local biosphere model used calculates carbon, water, and heat fluxes, and
required some climate and vegetation parameters as inputs. The model was
operated in 2000-2004 using meteorological data and MODIS data products.
We estimated spatial distributions in heat
and carbon fluxes at spatial resolution of 1*1 km, and validated an
adaptability of the model using measured data at the Takayama flux-site. As a
result, estimated GPP and heat fluxes had a good relationship to measured data.
We can precisely check on the accuracy of the model to estimate the
spatial and temporal patterns of the terrestrial carbon fluxes.
Author's Names: T. Sasai, K. Okamoto, K. Murakami, and Y. Yamaguchi
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ESTIMATING LANDSCAPE-LEVEL CARBON FLUXES FROM TOWER CO2 MIXING RATIO DATA
Description:
Variations
of the CO2 mixing ratio in the atmosphere near the surface result
from several processes, including photosynthesis and respiration of the
underlying ecosystems, vertical mixing near the surface and in the planetary
boundary layer (PBL), and entrainment of air above the PBL. We developed a
novel approach for isolating ecosystem metabolism signals at the landscape
scale (102-104 km2) in an hourly CO2
record using a vertical diffusion scheme coupled with an ecosystem model.
Author's Names: J.M. Chen, B. Chen, K. Higuchi, D. Chan, et al
Filesize: 33.38 Kb
Added on: 28-Jul-2005 Downloads: 145
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ESTIMATING THE CO2 FLUX FROM COARSE WOODY DEBRIS USING AUTOMATED AND MANUAL CHAMBER ...
Description: The CO2 flux from coarse woody debris (RCWD) in a deciduous broad-leaved forest was measured
using chamber measurements. The relationships between RCWD
and environmental factors, such as temperature (T)
and the water content (θ) of the
coarse woody debris (CWD), were determined from long-term continuous
measurements. Measurements of the RCWD
of many CWD samples revealed relationships between RCWD
and CWD characteristics, such as wood density (ρ)
and diameter (D).
A field survey conducted in 2003 estimated the mass of
CWD as 9.30tC·ha-1, with snags amounting to 60% of the total CWD
mass. Scaling RCWD to the ecosystem
while considering environmental factors according to the type (snag or log) of
CWD and CWD characteristics, we estimated that the annual RCWD
in the forest was 0.50tC·ha-1·y-1 in 2003. This came to
13-19% of the total heterotrophic respiration in the forest. The mean annual
CWD input mass from 2000 to 2004 was 0.61tC·ha-1·y-1.
Therefore, 0.11tC·ha-1·y-1 were sequestered by CWD, which
amounted to 7% of the net ecosystem production (NEP)
in the forest. In a younger forest, it is difficult to assume that the CWD
input and decomposition are balanced, so the RCWD
and CWD input mass should be quantified to evaluate the forest carbon cycle and
NEP.
Author's Names: M. Jomura, Y. Kominami, K. Tamai, T. Miyama, et al
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EVALUATION OF INTER-ANNUAL CARBON BUDGET FOR A SUB-ARCTIC BLACK SPRUCE FOREST BASED ON ...
Description: Measurements
of CO2 flux were made by the eddy correlation method over a sub-arctic
black spruce forest in interior Alaska.
Observed CO2 budget were sinks of -531~-247 and -219~0 g CO2
m-2 year-1 during 2003 and 2004, respectively. The broad
range is caused by uncertainty regarding assessment of the nocturnal fluxes. The
sequestration of CO2 during 2004 was limited by high temperature,
drought or low light intensity conditions. The net CO2 flux is in a
delicate balance between two large terms, which would shift from sink to source
due to global warming.
Author's Names: M.Ueyama, Y.Harazono, R.Okada, and A.Miyata
Filesize: 169.91 Kb
Added on: 08-Aug-2005 Downloads: 18
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FEASIBILITY OF EDDY COVARIANCE MEASUREMENTS OF THE ISOTOPIC COMPOSITION OF CO2 FLUXES ABOVE A ...
Description:
Better
quantification of atmosphere-ecosystem exchange of the isotopologues of CO2
could substantially improve our ability to probe underlying physiological and
ecological mechanisms controlling ecosystem carbon exchange, but the ability to
make long-term continuous measurements of the isotopic composition of exchange
fluxes has been limited by measurement difficulties. Quantum cascade (QC)
lasers are a new generation of infrared light sources that offer increased
stability and power for absorption spectroscopy applications (including the
measurement of isotope ratios in atmospheric CO2) and promise
substantial improvements over existing instruments: smaller size, increased
robustness, and most significantly for remote or long-term field deployments,
no need for cryogenic cooling of laser or detectors.
Author's Names: S.R. Saleska, J.H. Shorter, S. Herndon, et al
Filesize: 20.54 Kb
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FLUXES OF CO2, N2O, AND CH4 IN A COLD-TEMPERATE GRASSLAND SOIL OF NORTHERN JAPAN ESTIMATED ...
Description: Concentrations of 222Rn, CO2,
N2O and CH4 were measured in a cold-temperate northern
Japanese grassland soil during 1996 to compare the fluxes of CO2, N2O
and CH4 calculated by the 222Rn method and the static
chamber method and to estimate the source strengths of CO2 and N2O
in the soil using the 222Rn method. The 222Rn fluxes
ranged from 890 to 3400 dpm/m2/h
and the average was 1570±310 dpm/m2/h on sandy soil (50% sand). The
results of CO2, N2O and CH4
flux-measurements by the 222Rn method were in agreement with those
by the static chamber method within the observed range of error. The vertical
profiles of soil source
strengths of CO2
and N2O were also calculated from the concentration
gradients of 222Rn, CO2 and N2O to investigate
seasonal changes in the soil production rates of CO2
and N2O. The production rates of CO2 and N2O
varied significantly by season, averaging 1650±450 mgC/m3/h and
19±3.2 µgN/m3/h, respectively. These seasonal changes in the source
strengths of CO2 and N2O in the surface soil corresponded
with changes in fluxes of CO2 and N2O from the soil.
Author's Names: Yongwon Kim and Noriyuki Tanaka
Filesize: 62.26 Kb
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HISTORICAL CHANGES IN CARBON STORAGE OF THE EASTERN UNITED STATES: UNCERTAINTIES ASSOCIATED ...
Description: Process-based
models are important tools in assessments because they are able to integrate
mechanisms responsible for changes in carbon storage. Retrospective model
analyses are important for clarifying land use impacts on carbon storage
estimates. The objectives of our study were to: 1) develop a land use model
that allows annual conversion of native ecosystems to agriculture and creation
of age cohorts following harvest and cropland abandonment from 1600 to 2002; 2)
compare modeled age class distribution with independent inventory data on stand
age distributions, and 3) use these data sets to drive the Terrestrial
Ecosystem Model (TEM) and evaluate how assumptions about soil degradation and
CO2 fertilization influence estimates of changes in carbon storage
of the eastern US.
Author's Names: L.A. Joyce, A.D. McGuire, D.P. Coulson, J. Clein, T. Bumside
Filesize: 15.12 Kb
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HOW WELL DO WE NEED TO KNOW BIOMASS?
Description:
The
long-term net flux of carbon between terrestrial ecosystems and the atmosphere
has been dominated by two factors: changes in the area of forests and per
hectare changes in forest biomass resulting from management and regrowth. While
these factors are reasonably well documented in countries of the northern
mid-latitudes as a result of systematic forest inventories, they are uncertain
in the tropics. Recent estimates of carbon emissions from tropical
deforestation have focused on the uncertainty in rates of deforestation [Achard et al., 2002, 2004; DeFries et
al., 2002; Houghton, 2003]. By using the nearly the same data
for biomass, however, these studies have underestimated the total uncertainty
of tropical emissions and may have biased the estimates. In particular,
regional and country-specific estimates of forest biomass reported by three
successive assessments of tropical forest resources by the FAO [FAO/UNEP,
1981; FAO, 1995; FAO, 2001] indicate systematic changes in
biomass that have not been taken into account in recent estimates of tropical
carbon emissions. The ‘changes’ more likely represent improved information than
real on-the-ground changes in carbon storage. In either case, however, the data
have a significant effect on current estimates of carbon emissions from the
tropics and, hence, on understanding the global carbon balance.
Author's Names: R.A. Houghton
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IMPORTANCE OF RECENT SHIFTS IN SOIL THERMAL DYNAMICS ON GROWING SEASON LENGTH, PRODUCTIVITY, ...
Description: In
terrestrial high-latitude regions, observations indicate recent changes in snow
cover, permafrost, and soil freeze-thaw transitions due to climate change. These modifications may result in temporal
shifts in the growing season and the associated rates of terrestrial
productivity. Changes in productivity will influence the ability of these ecosystems
to sequester atmospheric CO2. We use the Terrestrial Ecosystem Model
(TEM), which simulates the soil thermal regime, in addition to terrestrial
carbon, nitrogen and water dynamics, to explore these issues over the years
1960-2100 in extratropical regions (30˚-90˚ N).
Our results reveal noteworthy changes in snow, permafrost, growing
season length, productivity, and net carbon uptake, indicating that prediction
of terrestrial carbon dynamics from one decade to the next will require that
large-scale models adequately take into account the corresponding changes in
soil thermal regimes.
Author's Names: E.S. Euskirchen, A.D. McGuire, D.W. Kicklighter, et al
Filesize: 60.62 Kb
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