CARBON STORAGE BY ASPEN-DOMINATED FORESTS OF THE UPPER GREAT LAKES REGION: PAST, PRESENT AND FUTURE
Description: Aspen-dominated forests occupy >4 million ha in the
upper Great Lakes region of the United
States and are an important reservoir for carbon
(C). Although harvesting and agriculture over the past century depleted C
stored in these forests, independent estimates suggest that forests in the
upper Great Lakes now are C sinks [Lee et al., 1999; Barford et al.,
2001; Birdsey et al, 2000]. However, C storage
by forests within the region varies considerably due to site disturbance
history, forest age, and interannual climate variability.
Author's Names: C.M. Gough, C.S. Vogel, H.P. Schmid, H-B. Su, P.S. Curtis
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IN AND OUT OF AFRICA: ESTIMATING THE CARBON EXCHANGE OF A CONTINENT
Description: Understanding
the diverse elements of the global carbon cycle has been the focus of much
recent research [Prentice et al.
2001, Schimel et al. 2001, Gurney et al. 2002, House et al. 2003]; research that is vital to our understanding of
the missing sink, future atmospheric carbon dioxide concentrations, and future
climate [Fan et al. 1998, Houghton et al.
1998]. Much research has concentrated on carbon dynamics of the large ocean
basins [Lee et al. 1998, Le Quéré et al. 2003] and terrestrial
exchange in North America and Eurasia [Pacala et al. 2000, Schimel et al. 2000]. Despite representing 20% of the global land
mass, Africa has thus far been largely
neglected in these studies. We will examine current understanding of carbon
stocks and fluxes within Africa and discuss
how uncertainty in global carbon dynamics arises in part from uncertainty in
the African components. We outline areas where new measurements and research in
Africa can contribute to understanding at both
continental and global scales.
Author's Names: N. P. Hanan, C.A. Williams, R.J. Scholes, et al
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TALL TOWER CARBON BUDGET MONITORING AND RESEARCH PROGRAMS IN HUNGARY
Description:
The
mixing ratio and the surface-atmosphere exchange of carbon dioxide have been
monitored at different elevations on a tall tower in West
Hungary (Hegyhátsál, 46o57'N, 16o39'E, 248 m
asl) since 1994 and 1997, respectively. The vertical mixing ratio profile
measurements along the 115 m tall tower has been completed with occasional
aircraft measurements up to 3000 m above the ground. The poster presents the
Hungarian tall tower site and the temporal variation of carbon dioxide observed
here. We discuss the region of influence determining the mixing ratio
variability, the so-called concentration footprint, as well as that of the flux
measurements. Methodological problems caused by the elevated monitoring levels,
and their solutions, are also given. The environmental factors governing the
net ecosystem exchange (NEE) of the vegetation are analyzed by means of a
process oriented ecosystem simulation model. It might be used to estimate the
future behavior of the region as the climate is changing. On the basis of the
measurements at Hegyhátsál a boundary layer model has been developed which can
give rough surface-atmosphere carbon dioxide flux estimate for sites where only
surface mixing ratio monitoring is available.
Author's Names: L. Haszpra, Z. Barcza, D. Hidy, T. Szabó, and K. Tarczay
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COMPARING THE IMPACTS OF DIFFERENT DISTURBANCES OF WESTERN NORTH AMERICAN FORESTS ON CARBON CYCLING
Description:
Two
major disturbances of forests in western North America
are fires and insect outbreaks. Much
research has focused on the effects of fires on the carbon cycle; little
research to date has occurred about outbreaks.
We are using observations, including field measurements and remotely
sensed imagery, together with ecosystem and insect population modeling improve
our understanding of these disturbances on carbon cycling.
Author's Names: J. A. Hicke, D. S. Ojima, J. A. Logan, D. Kashian, et al
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COMPARISON OF EDDY CO2 FLUXES MEASURED WITH OPEN-PATH AND CLOSED-PATH SYSTEMS BASED ON A LONG ...
Description:
Evaluation
of the difference between annual net CO2 ecosystem exchanges (NEE)
from the open- and the closed-path data is important for site intercomparison
studies. However, long-term measurements of NEE using both systems have been
limited. We report the comparison of eddy CO2 fluxes measured with
open- and closed path systems for three years from 2001 through 2003. The
annual GPP estimated from closed-path data was 8–10% less negative than that
from the open-path data, whereas the annual RE was 11–16% more positive for
closed-path data. Consequently, the annual NEE from the closed-path data was
less negative by 301–333 gC m-2 y-1. The bias of NEE
between two systems is large and an extremely important issue. Ecophysiological
approaches are needed to validate of the eddy covariance technique.
Author's Names: R. Hirata, T. Hirano, N. Saigusa, Y. Fujinuma, et al
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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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SIGNALS OF PHOTOSYNTHESIS AND RESPIRATION AT BOREAL FORESTS IN RESPONSE TO ENVIRONMENT ...
Description: The isotopic composition of the ecosystem respiration (d13CER) and the isotopic
discrimination of the ecosystem (DEco) were retrieved from intensive campaigns (1998 to 2000) and
from weekly diurnal sampling (2003) at a boreal forest site (Fraserdale, Canada,
49°53'N, 81°34'W). The results show that
d13CER was less sensitive to
temperature (T) variation compared with DEco, suggesting that the photosynthesis CO2 flux
was likely more sensitive to temperature than the ecosystem respiration CO2
flux during the same period of time at the study site.
Author's Names: L.Huang, B. Chen, P.P. Tans, K.Higuchi, D.Worthy, et al
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THE UNDERPINNINGS OF LAND-USE HISTORY: THREE CENTURIES OF GLOBAL GRIDDED LAND-USE ...
Description: To accurately assess the
impacts of human land-use on the Earth System, information is needed on the
current and historical patterns of land-use activities. Previous global
studies have focused on developing reconstructions of the spatial patterns of
agriculture. Here, we provide the first global gridded estimates of the
underlying land conversions (land-use transitions), wood harvesting, and
resulting secondary lands annually, for the period 1700-2000. For input, we
used two existing datasets of global gridded land-use history—HYDE [Klein Goldewijk 2001] and SAGE [Ramankutty & Foley 1999], a new
reconstruction of national wood harvest that we spatially disaggregated to a
global gridded product, and model estimates of the spatial distribution of
plant carbon density and its recovery. Since these do not fully constrain the
problem, we added assumptions related to four additional factors: the residence
time of agricultural land, the inclusiveness of wood harvest statistics, the
priority for land conversion and logging (e.g. primary- or secondary-land), and
the spatial pattern of wood harvest within countries. In order to estimate
uncertainty and characterize model sensitivity, a set of 216 alternative reconstructions
was derived using different assumptions. We estimate that the accumulated
global wood harvest 1700-2000 was approximately 112 Pg C including slash.
Author's Names: G.C. Hurtt, S. Frolking, M.G. Fearon, B. Moore III, 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
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CROSS-COMPARISON OF THE DECADAL TRENDS IN CARBON BUDGET OF TERRESTRIAL ECOSYSTEMS ESTIMATED BY DIFFE
Description:
There remain large uncertainties in our model estimations of
terrestrial CO2 budget at broad scales. We used two terrestrial
carbon cycle models (Sim-CYCLE and SASAI) and three climate datasets
(NCEP/NCAR, NCEP/DOE, and ERA40) for the period from 1982 to 2001 and performed
cross-comparison, aiming at clarifying the source of uncertainties. Using the
same model, different carbon budgets were obtained by the three climate
datasets, globally due to the difference in solar radiation and locally due to
precipitation. The two models, which differ in canopy processes, estimated
different temporal trends and spatial patterns of CO2 budget during
the experimental period. This study exemplified the necessity of developments
in both models and datasets.
Author's Names: Akihiko Ito and Takahiro Sasai
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