SYNTHESIS OF TOP-DOWN AND BOTTOM-UP SCALING OF REGIONAL TERRESTRIAL CARBON DIOXIDE ...
Description: Quantifying the
regional scale (10-1000 km) exchange of carbon dioxide between terrestrial
ecosystems and the atmosphere is vital for understanding the spatial and
temporal variation in global CO2 flux. Multiple investigations of
top-down and bottom-up regional flux scaling are currently underway in the
northern Great Lakes region, USA. Landscape and regional scale CO2
fluxes from multiple line of evidence, including eddy covariance multi-tower
aggregation, tall-tower flux footprint decomposition, ecosystem modeling, CO2
mixing ratio boundary layer budgets and regional inversions reveal variations
in CO2 flux arising from variations in vegetation type, canopy
structure and interannual climate variability. With careful calibration, encouraging
consistency is seen from several independent regional flux estimates. Without
parameter optimization and high resolution maps of land cover, global scale
remote-sensing and ecosystem-model CO2 flux estimates fail to
accurately capture the local regional CO2 flux. These results
represent a first attempt to cross-compare multiple top-down and bottom-up
regional flux estimates.
Author's Names: A.R. Desai, W. Wang, D.M. Ricciuto, B.D. Cook, et al
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CONTINUOUS IN SITU MEASUREMENTS OF ATMOSPHERIC O2 AND CO2
Description: Simultaneous
and continuous measurements of O2 and CO2 made in
the air around terrestrial ecosystems have the potential to improve our
understanding of the biogeochemistry of the ecosystem, and may reduce
uncertainties in estimates of terrestrial carbon uptake derived from
atmospheric O2 measurements. Following the
design of Stephens et al. [2001], we
have constructed an instrument that performs continuous in situ measurements of atmospheric O2 and CO2
concentrations. We present design and performance data, along with preliminary
results from a deployment at the Environmental Measurement Site at Harvard Forest
in central Massachusetts.
Author's Names: M.O. Battle, R. Perry, E. Sofen, J. Carpenter, B.B. Stephens
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Added on: 25-Jul-2005 Downloads: 40
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EFFECT OF RESPIRATION AND CANOPY PARAMETERIZATIONS ON MODELED CARBON FLUX
Description: Simulations
of the global carbon cycle are strongly dependent upon model representations of
the exchange of carbon, energy, moisture and momentum between the atmosphere
and terrestrial biosphere. The carbon flux produced by these biophysical models
is subsequently dependent on the method used to produce respiration and
photosynthesis within the model on both spatial and temporal scales. We use an
updated version of the Simple Biosphere Model (SiB3) to simulate global carbon
flux between atmosphere and land surface, and compare model results to flux
tower and flask network observations. SiB3 assumes no annual net source or sink
of carbon in each gridcell, but the spatial pattern and seasonality of carbon
flux and atmospheric concentration can be strongly influenced by
parameterization of heterotrophic and autotrophic respiration and the
representation of vegetation phenology.
Author's Names: I.T. Baker, K.M. Schaefer and A.W. Philpott
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ANNUAL CARBON DIOXIDE DRAWDOWN AND THE NORTHERN ANNULAR MODE
Description:
Year-to-year variations in summer drawdown of northern
hemisphere atmospheric carbon dioxide (CO2) are compared with
corresponding year-to-year variations in sea- level pressure (SLP), surface air
temperature and the productivity of land vegetation as inferred from the
satellite-derived normalized difference vegetation index (NDVI). Annual values
of CO2 drawdown for the years 1980-2000 are estimated from smoothed
time series derived directly from individual flask samples at the 9 northern
hemisphere monitoring stations with the most continuous records. The leading
principal component of the 9 standardized drawdown time series, in which all
stations exhibit positive loadings, is used to represent the hemispheric signal
in the CO2 drawdown. Linear regression analysis is used to infer the
spatial patterns of anomalies in sea level pressure, surface air temperature
and the NDVI observed during various seasons of years in which the drawdown is
anomalously strong.
Author's Names: J.L. Russell, E. Shevliakova, S. Malyshev, and J.M. Wallace
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Added on: 04-Aug-2005 Downloads: 42
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REGIONAL-SCALE CHARACTERIZATION OF SUMMERTIME CO2 SOURCES AND SINKS OVER THE CONTERMINOUS ...
Description:
Fast-response
(1-s resolution) CO2 measurements were recorded aboard the NASA DC-8
during the Intercontinental Chemical Transport Experiment – North
America (INTEX-NA) mission.
Utilizing a non-dispersive infrared gas analyzer-based sampling
system, measurements were obtained over sparsely sampled areas of North America and adjacent ocean basins providing
valuable regional-scale information on carbon sources and sinks.
Author's Names: S.A. Vay, Y. Choi, J.-H. Woo, and K. Prasad
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Added on: 08-Aug-2005 Downloads: 42
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THE CANADIAN TERRESTRIAL ECOSYSTEM MODEL (CTEM) – THE TERRESTRIAL CARBON CYCLE COMPONENT OF THE ..
Description: The
Canadian Centre for Climate Modelling and Analysis (CCCma) is currently working
towards development of a coupled carbon climate model in which the time-evolving
atmospheric concentrations of greenhouse gases, and in particular CO2,
are computed prognostically on the basis of scenario-specific emissions. The
Canadian Model for Ocean Carbon (CMOC) and the Canadian Terrestrial Ecosystem
Model (CTEM) are the oceanic and terrestrial carbon cycle models implemented in
this coupled framework. This presentation will focus on the terrestrial carbon
cycle component CTEM that is able to grow vegetation from bare ground and
includes processes of photosynthesis, autotrophic and heterotrophic
respiration, phenology, allocation, mortality, land use change, fire, and
competition between plant functional types (PFTs). In the coupled model CTEM
provides a dynamic land surface interface to the climate model by simulating time-varying
vegetation structural attributes as a function of model climate and provides net
fluxes of CO2 between the land surface and the atmosphere. This
presentation provides an overview of how the primary terrestrial ecosystem
processes are modeled in CTEM. It also discusses in some detail the parameterizations
of fire and competition among plant functional types (PFTs). These two
processes have not received adequate attention in the current generation of dynamic
global vegetation models. The fire module of CTEM takes into account all three
aspects of the fire triangle: fuel availability, readiness of fuel to burn
depending on weather conditions, and the presence of an ignition source. The
approach also takes into account the anthropogenic effect on natural fire
regimes. Competition between PFTs is modeled on the basis of a modified form of
Lotka-Volterra equations that, unlike existing applications, allows coexisting
PFTs. Model results at selected locations show that CTEM estimates of vegetation
biomass, leaf area index, fire return interval, biomass burning CO2
emissions and fractional coverages of coexisting PFTs compare reasonably well
with observation-based estimates.
Author's Names: Vivek Arora
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AIRCRAFT TO INVENTORES: A MULTISCALED INVESTIGATION OF CARBON FLUXES IN A MONTANE LANDSCAPE
Description: As a result of landuse, 50%
or more of forests in the Northern Hemisphere mid-latitudes are in hilly to
mountainous terrain, accounting for half or more of the mid-latitude Gross
Primary Productivity. The mid-latitude sink observed in the atmosphere may
reflect carbon dynamics occurring in complex terrain. This is challenging: these regions are
inherently highly heterogeneous and currently reflect complex land use
histories, and atmospheric techniques for estimating spatially integrated
carbon fluxes don’t work well in sloping terrain. Consequently, the impacts of
climate, harvesting regimes, disturbances and fire/pest management on carbon
exchange are poorly constrained in mountains. While mountains are
heterogeneous, the orientation of slopes to incident radiation and
gravitational flows of air and water result in organization of the variability
that can be exploited. Analysis using model-data fusion techniques of long-term
eddy covariance data showed 1) mid-aged Rocky Mountain forests are sinks, 2)
most of the net uptake occurs in the spring when melting snow provides moisture
for photosynthesis but low soil temperatures inhibit respiration and 3)
interannual variability is mainly due to GEE and is largely driven by spring
temperature and precipitation, which both determine spring fluxes and set the
stage for mid-summer soil moisture conditions.
Author's Names: David Schimel, Britton Stephens, Russell Monson, et al
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ALLOCATION AND RESIDENCE TIME OF CURRENT PHOTOSYNTHETIC PRODUCTS IN A BOREAL FOREST USING ...
Description:
We tested the utility of a low-level radiocarbon
(14C) pulse-chase label for quantifying carbon allocation patterns
and the contributions of different components to total ecosystem respiration at
ambient CO2 concentrations in a black spruce forest stand in central
Manitoba, Canada. Approximately .01 moles of CO2
that was isotopically enriched in 14C to ~100,000 times background
atmospheric 14C levels was introduced into the headspace of a 37,000
L translucent dome enclosure. Over a one
hour period, ~70% of this label was photosynthetically assimilated by the
enclosed vegetation. The label application produced a 14C signature
well below regulated health standards, and was easily detectable with
Accelerator Mass Spectrometry (AMS). We followed the allocation and timing of
labeled photosynthetic products by measuring the amount and 14C
content of CO2 respired from different ecosystem components over the
following 30 days.
Author's Names: M.S. Carbone, C.I. Czimczik, K.E. McDuffee, S.E. Trumbore
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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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APPARENT TRENDS IN PHOTOSYNTHETIC CAPACITY OF MONSOON ASIA FROM 1982 TO 2002
Description: The
rapid economic growth of Monsoon Asia raises concerns about the future of
carbon stored in the terrestrial ecosystems of the region, especially in connection
with climate change [Tian et al.,
2003; Canadell et al., 2002; Oikawa and Ito, 2001; Esser, 1995]. The regional carbon budget
for 1980s suggests that Monsoon Asia as a whole acted as source [Tian et al., 2003], although some parts of
the region acted as sink. Here we provide some evidence from satellite data
that photosynthetic capacity of the region changed in the manner that suggests
similar conclusion. Comparing the period 1982-1992 and the period 1992-2002, we
found that the photosynthetic capacity of the territory generally decreased in
the forest zone and increased in the non-forest zone of the region.
Author's Names: G. A. Alexandrov, T. Oikawa, and Y. Yamagata
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