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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Added on: 29-Jul-2005 Downloads: 32
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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
Filesize: 18.80 Kb
Added on: 29-Jul-2005 Downloads: 21
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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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Added on: 01-Aug-2005 Downloads: 21
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CHANGING SOURCES OF SOIL RESPIRATION WITH TIME SINCE FIRE IN A BOREAL FOREST
Description:
Stand-replacing
crown fires in boreal spruce forests initiate a vegetation succession from
forbs to deciduous trees to coniferous trees. Soils are warmest during the
first decades and cool throughout the succession as shading by trees and cover
with bryophytes and plant litter increase. It was postulated that the initially
warmer soil temperatures enhance decomposition of soil organic matter (SOM) by
microorganisms, and that decomposition would release similar amounts of CO2
as combustion during fire [Auclair and
Carter, 1993].
Author's Names: C.I. Czimczik, M.S. Carbone, G.C. Winston, and S.E. Trumbore
Filesize: 139.51 Kb
Added on: 28-Jul-2005 Downloads: 22
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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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CARBON SEQUESTRATION IN SITES REFORESTED IN NORTHERN MEXICO
Description:
Reforestation
is an important mean to protect soils, to restore habitat for plants and
animals, to regulate the hydrological cycle, to recharge aquifers, to produce
oxygen and to sequester carbon dioxide. Global warming concerns are prompting reforestation
practices and studies dealing with biomass production and carbon sequestration
by exotic and native species. This research presents information on biomass and
carbon sequestration projections in reforested sites of northern Mexico.
A total of 124 sampling plots were sampled for dasometric features and biomass
components in the Mexican states of Durango, Coahuila,
and Nuevo Leon of the
Eastern and Western mountain ranges of northern Mexico. Results showed the
potential carbon sequestration and biomass projections by component for each of
three main regions separated by multivariate statistics and productivity
curves. Mean annual carbon sequestration rates approach 3.90, 0.90, and 0.45 Mg ha-1
y-1 for reforested sites of the States of Durango, Nuevo Leon, and
Coahuila, respectively. Native species of coniferous forests of Durango (P. durangensis, P. cooperii, and P. engelmannii)
and Nuevo Leon (P.
pseudostrobus) sequester carbon at higher rates than the introduced pine
species of Durango (P. arizonica), Nuevo Leon
(P. cembroides, P. pinceana, and P. nelsoni), and Coahuila (P. halepensis). Stands reforested are sequestered carbon at a higher
rate than stands of native coniferous forests because of the largest plant
density of the former sites, therefore they provide additional environmental
benefits.
Author's Names: J. Návar1, and F.J. Rodriguez
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Added on: 03-Aug-2005 Downloads: 27
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CARBON SEQUESTRATION IN AGRICULTURAL SOILS OF DIFFERENT NATURAL FERTILITY UNDER NITROGEN USAGE
Description:
The
influence of nitrogen fertilizing on carbon accumulation and decomposition in
arable soils of different fertility – gray forest soil and chernozem was
investigated in greenhouse experiment with corn. Growing of plants without N application on rich chernozem favored
the considerable (about 1% of Сorg) C
growth, and on poor gray forest soil contributed to C decrease. Soil organic
matter (SOM) decomposition in both soils under unfertilized plants was the
same. N usage on gray forest soil resulted in increase of C accumulation due to
the substantial increase of C input with roots of fertilized plants and as organic matter active phase of this soil was stable
against decomposition under N. N application on chernozem in reverse
significantly increased SOM decomposition and affected plant productivity to a
lesser degree. Thus, N fertilizing favors C sink in arable soils of low
fertility and can reduce soil C
accumulation in arable soils of high fertility.
Author's Names: A.S. Tulina, T.V. Kuznetsova, and V.M. Semenov
Filesize: 89.25 Kb
Added on: 08-Aug-2005 Downloads: 19
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CARBON FLUXES RESULTING FROM LAND-USE CHANGES IN THE STATE OF MORELOS, MEXICO
Description:
This report presents information on land use changes and
carbon stocks and fluxes resulting from land use-change in the subtropical dry
forest of the State of Morelos, Mexico.
Biomass components of standing vegetation were estimated from 40 quadrats (400
m2 each) distributed across this ecosystem. Regional land use
changes using forest cover for two different periods (1976 and 1993) and
present forest cover, as well as measurements of soil organic matter and soil
organic carbon were used to predict carbon stocks and fluxes in this ecosystem.
The results showed for the period of 1976-1993 that the annual deforestation
rate is 0.87% indicating that approximately 20,000 ha of subtropical dry forest
were lost during this period and that 57% of the original ecosystem has been
lost since 1950. On the other side, intensive agriculture, including induced
grasslands increased (22 000 ha) 15% of the total studied area largely at the
expense of the tropical dry forest. Land use changes from the subtropical dry forest
to agriculture contributed to carbon emissions of 6.49 Tg, of which standing
biomass averaged 2.79 (± 0.28) Tg, root biomass averaged
1.75 (± 0.18) Tg, and soil organic carbon averaged 1.95 ( ±
0.2) Tg. Projected land-use changes will likely contribute to an additional
carbon flux of 2.88 (± 0.14) Tg by the year 2050.
Practices to conserve, sequester, and transfer carbon stocks in this ecosystem
are discussed as a means to reduce carbon flux by deforestation practices.
Author's Names: J. Návar and A.L. Estrada
Filesize: 73.08 Kb
Added on: 03-Aug-2005 Downloads: 23
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CARBON FLUXES AND LAI EVOLUTION IN THE ECMWF LAND SURFACE SCHEME
Description:
The
Ags parameterization of canopy conductance from ISBA-Ags is implemented in
TESSEL, the ECMWF land surface scheme. We present first results of the
investigation of the model behavior in view of an operational use in a data
assimilation system. It is shown that the performance of the Ags module is
sensitive to the land surface model in which it is embedded.
Author's Names: M.H. Voogt, L. Jarlan and B.J.J.M. van den Hurk
Filesize: 100.53 Kb
Added on: 08-Aug-2005 Downloads: 29
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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
Filesize: 72.28 Kb
Added on: 02-Aug-2005 Downloads: 24
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