TEMPORAL AND SPATIAL VARIABILITY OF CO2-CH4 SOURCE-SINK STRENGTH IN NORDIC ECOSYSTEMS
Description: In 2003 a Nordic Centre of Excellence on Ecosystem
Carbon Exchange and Its Interactions with the Climate System, NECC, was
initiated. The center comprises practically all eddy covariance flux sites (ca.
25) in the Nordic countries which, represents wetlands, coniferous and deciduous
forests, ‘Kyoto’
forests, lakes, agricultural sites and one urban site. The forest sites cover a
range of age classes and management practices, and long-term sites with more
than 8-10 years of continuous flux data. The center has also access to a flux
aircraft for regional assessments and involves high precision CO2
and CH4 measurements in high towers. A synthesis of the current
sink/source strength of CO2 and CH4 of the different
ecosystems is in preparation and will be presented. Analysis of long-term data
from a few sites and how it relates to annual parameters is also presented.
Author's Names: A. Lindroth
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INTERANNUAL VARIABILITY IN SOIL RESPIRATION OF FOREST, ...
Description:
Annual and seasonal dynamics of
total soil respiration (TSR) of sandy Albeluvisols and clay Phaeozems under
forest, grassland, and arable were studied in situ (Russia, Moscow Region). Measurements
of soil CO2 emission were carried out by closed chamber method from
November 1997 through October 2003 weekly. The highest mean TSR (806+86
g C·m-2·yr-1) was observed for sandy Albeluvisols under
grassland. It significantly exceeded the annual CO2 fluxes from
soils of other ecosystems (P< 0.1). The lowest value of mean annual TSR was
observed for arable clay Phaeozems (361+55 g C·m-2·yr-1).
It was reliably lower than in soils of the other cenoses (P<0.5). No significant
differences were found between annual amounts of CO2 emitted from
Albeluvisols under forest and Phaeozems under forest and grassland. The interannual
variability of TSR caused by the difference of weather conditions was 30% on average and ranged
from 25-26% (forest and grassland ecosystems on Albeluvisols) to 37% (agroecosystem
on Phaeozems). We found that TSR in natural ecosystems positively correlated
with the total annual precipitation and sum of precipitation for the spring season
(R=0.73-0.90, P<0.1). The share of the cold period (November-April) to the annual
CO2 flux was substantial and averaged 22-25% and 17% for natural and
agricultural ecosystems, respectively. Therefore, emission of CO2 during the cold
period was an essential part of the annual CO2 fluxes from soils of
sub-boreal zone, which should be taken into account while calculating the
carbon budget for the whole year.
Author's Names: V.O. Lopes de Gerenyu, I.N. Kurganova, L.N. Rozanova, et al
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ON-LINE SIMULATION STUDY OF THE CARBON CYCLE BETWEEN LAND SURFACE AND THE ATMOSPHERE USING ...
Description:
A
land surface model (Biosphere-Atmosphere Interaction Model Ver.2: BAIM2) can
estimate not only the energy fluxes, but also the carbon dioxide flux between
terrestrial ecosystems and the atmosphere. The photosynthesis processes for C3
and C4 plants are adopted in the model. The carbon storage of
vegetation is divided into five components (leaves, trunk, root, litter, and
soil), and the carbon exchanges among the components of vegetation and the
atmosphere are estimated in each time step of the on-line model integration.
The values of morphological parameters using in the model are derived from the
carbon storage values of the components, and the phenological changes of
vegetation are reproduced by the model. The BAIM2 was incorporated into a
spectral general circulation model, and was connected on-line to the atmospheric
model. Using this climate model, an experimental control time integration was
performed under the actual global vegetation condition. After the control time
integration, the vegetation types of Southeast Asia
were changed to the C4 grass, and the vegetation change impact
integration was performed. The results of the impact experiment were compared
with the results of the control. In the Indochina Peninsula
area, by the vegetation change from the tropical seasonal forest to the C4
grass, year mean values of the NPP generally increased, and those of the NEP also increased. On the other hand, in the
maritime continent area, by the change from the tropical rain forest to the C4
grass, the NPP values generally decreased, and the NEP
values also decreased. It was considered that the differences of phenological
changes of vegetation in these areas and the differences of climatic impact of
vegetation changes induced the different change phenomena of the carbon cycles.
There is a possibility that the influences of the vegetation changes
(deforestation) on the carbon cycles are different in the area where the
original vegetation types are different.
Author's Names: K. Mabuchi and H. Kida
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CO2 LOSSES FROM AGRICULTURAL SOILS IN NORTHERN KAZAKHSTAN AS AFFECTED BY PHYSIOLOGICAL STATE ...
Description:
Dynamics of organic matter in agricultural soils
attract significant interest because of strong impact on global climate. Steppe
ecosystems are considered as having high potential to preserve global carbon
and are located mainly in arid and semiarid areas with annual precipitation
smaller than 400 mm. Steppe ecosystems of the wheat belt in Kazakhstan have annual
precipitation 250 to 350 mm. Here is our attempt to evaluate whether microbial
quotients could be applied to evaluate the potential of soil to act as sink for
CO2.
Author's Names: A. Mamilov, O. Dilly
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ADVECTIVE TRANSPORT OF CO2 IN PERMEABLE MEDIA INDUCED BY ATMOSPHERIC PRESSURE FLUCTUATIONS
Description:
Pressure fluctuations at the earth’s
surface are caused by a variety of atmospheric phenomena. Examples include low
frequency barometric pressure variations, high frequency atmospheric
turbulence, atmospheric gravity waves, and quasi-static pressure fields created
as wind blows over or around topographic features, like buildings, hills, wind
breaks, etc. These naturally occurring pressure fields cause air to move in and
out of soils, snowpacks, and other permeable media. Consequently, the uptake or
release of trace gases from soils and snowpacks is a combination of molecular
diffusion and advective flows caused by surface pressure fluctuations. Such
pressure forcing has been found to influence the exchange rate of many trace
gases from the underlying substrate to the atmosphere. Given the importance of
these trace gases to understanding biogeochemical cycling and global change, it
is crucial to quantify (as much as possible) any impact these advective flows
can have on gas transport within soils and snowpacks.
Author's Names: W. J. Massman
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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
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INFLUENCES OF CANOPY PHOTOSYNTHESIS AND SUMMER RAIN PULSES ON ROOT DYNAMICS AND SOIL ...
Description:
The first objective of this paper is to make the link between the
seasonality of fine root dynamics and soil respiration in a ponderosa pine (Pinus ponderosa P. & C. Lawson)
plantation located in the Sierra Nevada of California. The second objective is
to better understand how canopy photosynthesis influences fine root initiation,
growth and mortality in this ecosystem. We compared CO2 flux
measurements (NEE, soil CO2 efflux) with aboveground and belowground
root dynamics. Soil respiration was measured in a control and a trenched plot
to separate heterotrophic and autotrophic soil respiration.
Author's Names: L. Misson, A. Gershenson, J. Tang, R. Boniello, et al
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SEASONAL VARIATION AND PARTITIONING OF NOCTURNAL FOREST LEVEL RESPIRATION IN A MIXED BROADLEAVED ...
Description:
Seasonal variations in nocturnal
aboveground forest level respiration were measured using static, automated
foliage and stem chambers in the Yamashiro Experimental Forest (YEF), a
broadleaved secondary forest in Kyoto,
Japan. The
growth component of the respiration during the growing season equaled 12% of
the total annual aboveground nocturnal forest level respiration in the YEF.
These findings suggest that growth respiration is an important component of
total respiration in similar forests.
Author's Names: T. Miyama, Y. Kominami, I. Hosoda, K. Tamai, et al
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CARBON DIOXIDE EFFLUX FROM THE FOREST FLOOR IN A DECIDUOUS FOREST IN JAPAN -- AN IMPROVED ...
Description:
Some infrared CO2
sensors, such as GMD20 and GMT222
(VAISALA), are widely used for soil CO2 efflux measurements despite
the fact they have a slow response rate. The output signal is delayed both from
diffusion processes in the sample cell and internal averaging calculations
necessary for stable data output. For accurate estimations of CO2
efflux, we therefore need to know the actual increase in CO2
concentration in a chamber without composite delays. To parameterize these
delays, we conducted laboratory experiments to determine the response
characteristics of sensors under diffusion and flow-through conditions. Next,
we developed a backward calculation method for estimation of the actual CO2
concentration increase using the delayed sensor output (BCDC: Backward
calculation for delay compensation). The results showed that the slow response
of sensors caused large estimation errors in CO2 efflux
measurements. In the case of GMT222,
a 10% underestimation was suggested when the soil CO2 efflux was
calculated with non-corrected data using a nonlinear regression method with
sampling intervals of 300 seconds. Thus, correction of the sensor response with
a backward estimation might be effective. We also calculated and evaluated the CO2
efflux from a forest floor in a deciduous forest employing the BCDC method.
Author's Names: Y. Mizoguchi, Y. Ohtani, T. Watanabe, and Y. Yasuda
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OBSERVATIONAL UNCERTAINTIES IN NET ECOSYSTEM CO2 EXCHANGE
Description:
Measurements of net ecosystem CO2 exchange
using continental tower flux networks provide a critical constraint in models
of regional and global carbon budgets. Uncertainty exists in these measurements
due to the effects of complex terrain and vegetation gradients. Using an array
of seven towers distributed across a mountain landscape, we estimated that a
significant error exists in the five-year record of measured net ecosystem CO2
exchange. The error was due to the previously ignored influence of advective CO2
fluxes. When this error was rectified by explicit consideration of the
advective flux components, the forest was predicted to exhibit a 38% higher
potential for carbon sequestration than previously thought.
Author's Names: R. Monson, C. Yi, D. Anderson, J. Sun, B. Lamb, et al
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