PARTITIONING OF ROOT AND MICROBIAL RESPIRATION IN SOIL: COMPARISON OF THREE METHODS
Description:
Three techniques for separation of total CO2 efflux from soil
into root and microbial respiration were compared: component integration, root
exclusion and pulse labelling of shoots in 14CO2
atmosphere. The contribution of rhizosphere to total CO2 efflux from
soil varied from 19 to 49% (including root respiration amounted to 9-32%). The
share of non-rhizosphere respiration was 51-80%. The results obtained by
component integration and root exclusion techniques were similar. Rhizosphere
respiration estimated by pulse labelling were less as estimated by two
non-isotopic methods.
Author's Names: D.V. Sapronov, Y. Kuzyakov
Filesize: 145.98 Kb
Added on: 04-Aug-2005 Downloads: 29
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INFERRING FLUXES OF BIOMASS BURNING FROM A GLOBAL CARBON CYCLE DATA ASSIMILATION SYSTEM
Description: The Carbon Cycle Data Assimilation System (CCDAS) infers
values of the parameters controlling the function of a process model of the
terrestrial biosphere using various observations. An obvious restriction of
this approach is the limitation by the dynamics of the underlying process model.
Careful study of the model-data mismatch and analysis of residuals can alert us
to the presence of systematic errors which then candidate processes to extend the
terrestrial biosphere model and the assimilation system. In a previous study, Rayner et al. [2005] noticed systematic underestimate of
carbon release events in the tropics. The most likely explanation for this was
the absence of any model of biomass burning in the biosphere model used in that
study. Here, we extend CCDAS to infer the spatial and temporal patterns of
biomass burning in the period 1979-1999. In a first attempt we include some
flux components to account for missing processes. This so-called weak
constraint form avoids biasing the inferences since the underlying model is no
longer forced to match data without necessary processes. Also the magnitudes of
the extra inferred fluxes quantify the missing processes.
Author's Names: M. Scholze, P. Rayner, W. Knorr, T. Kaminski, et al
Filesize: 12.15 Kb
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NEW ESTIMATES OF LIVE BIOMASS AND NET PRIMARY PRODUCTION OF RUSSIAN FORESTS: A FOOTPRINT OF ...
Description: The
paper presents new estimates of live biomass (phytomass) and net primary production
(NPP) of Russian forests for 1993 and 2003. These indicators are estimated
based on forest inventory data and a specially developed semi-empirical modeling
system. The latter contains regional
models of growth by major forest forming species, multi-dimensional models of
phytomass and models of biological production. It is shown that the fractional
structure of forest phytomass substantially differs from previous estimates
that indicated significant temporal trends of the share of aboveground wood
(AGW), green part (GP) and belowground (BG) phytomass. The total forest NPP (of
307 g C m-2yr-1 for 2003) is substantially higher than
previously reported. These changes may
be attributed to climatic change which was dramatic over the last four decades,
particularly in Asian Russia.
Author's Names: A. Shvidenko, D. Shepashenko, S. Nilsson, and A. Lapenis
Filesize: 41.29 Kb
Added on: 04-Aug-2005 Downloads: 23
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TOWARDS A BETTER QUANTIFICATION OF CROPLANDS EXTENT AND MANAGEMENT CONTRIBUTION TO CARBON CYCLING
Description: The
development of agriculture responding to increasing demand for food raises the
question of the role of cultivated land in relation to carbon sources and
sinks, their spatial patterns and temporal variability.
Author's Names: P.C. Smith, N. Viovy, Y. Meurdesoif, S. Gervois, et al
Filesize: 71.66 Kb
Added on: 04-Aug-2005 Downloads: 20
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PROBLEM OF ESTIMATING WILDFIRES IMPACT ON CARBON CONTENT IN ATMOSPHERE
Description: During photosynthesis,
atmospheric carbon sequestration goes on at the expense of formation and
accumulation of organic substance, and an inverse process (carbon emission in
the atmosphere) takes place during decomposition and oxidation of this organic
substance. On land, in non-swamp ecosystems, these processes are balanced as a
whole both under climax forms and interchange of: 1) periods of active
oxidation of organic substance under influence of disturbing factors (more
often, fires), and 2) periods of active formation of organic substance in the
process of regeneration successions.
Author's Names: A.V. Volokitina, T.M.Sofronova, and M.A.Sofronov
Filesize: 22.51 Kb
Added on: 04-Aug-2005 Downloads: 28
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MODELING DAILY AND SEASONAL DYNAMICS OF CO2 STABLE CARBON ISOTOPIC EXCHANGE BETWEEN BOREAL ...
Description:
In
this study, we developed an integrated modeling system to simulate dynamics of a
stable carbon isotope of CO2, moisture, energy, and momentum between
boreal ecosystems and the atmosphere as well as their diffusion processes
through the whole convective boundary layer (CBL), using remotely sensed
surface parameters to characterize the surface heterogeneity, and the marine
boundary layer matrix data to represent the CBL top condition. Model validation
and primary results in boreal ecosystems were presented in this paper.
Author's Names: B. Chen, J. M. Chen, L. Huang, and P. Tans
Filesize: 145.58 Kb
Added on: 05-Aug-2005 Downloads: 24
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DIRECT COMPARISON OF EDDY COVARIANCE AND BOWEN RATIO ENERGY BALANCE MEASUREMENTS OF CO2 FLUXES ...
Description: The objectives of this study were to (1) compare
annual mass and energy fluxes of sensible carbon dioxide (CO2), heat
flux density (H), and latent heat flux density (LE) from Campbell Scientific,
Inc. (CSI) manufactured eddy
covariance (EC) and Bowen Ratio/energy balance (BREB) instrumentation in a
tallgrass prairie site and (2) make similar short term (5-14 d) comparison in
other grazing ecosystems throughout the western United States. The long-term
tallgrass prairie site was located in central Oklahoma
with measurements being made from August 2001- October 2004, while the
short-term sites were located in Oregon, Colorado, Idaho, North Dakota, and Arizona
during the summers of 2003 and 2005. Results from the long-term (< 36-month)
co-located EC and BREB units indicated that both systems demonstrated similar
seasonal patterns, yet the EC consistently failed to close the energy balance
by 25-35% when compared to the BREB.
Author's Names: G.L. Doyle, W.A. Dugas, and H. Mayeux
Filesize: 13.37 Kb
Added on: 05-Aug-2005 Downloads: 18
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DIAGNOSING CONTROLS OVER GPP AND ECOSYSTEM RESPIRATION USING FLUX DATA AND ASSIMILATION MODELING
Description: We used data assimilation to estimate the
contributions of GPP, heterotrophic (Rh) and autotrophic (Ra) respiration to
Net Ecosystem Exchange at the Niwot Ridge long-term eddy covariance site using
5 years of data. The assimilation problem is solved by optimizing state and
parameter values in a version of the PnET ecosystem model by minimizing the
misfit between modeled and observed NEE, subject to Bayesian prior estimates of
the model parameters and initial state. Seventeen free parameters, about half
of the total, are estimated, with the remaining parameters defined from other
studies. The model computes GPP, Rh and Ra fluxes for each day and night, and
thus produces an estimate of the separation of NEE into its components. We
checked the model’s partitioning of the NEE into GPP and total respiration by
comparing the modeled and observed diurnal NEE cycle, and evaluated the Rh-Ra
partitioning by comparing modeled and observed Net Primary Productivity, which
constrains this partitioning since GPP- Ra=NPP. While some discrepancies exist,
overall the assimilation model had considerable skill on diurnal to interannual
timescales.
Author's Names: W. Sacks, D. Schimel, R. Monson, G. Churkina
Filesize: 12.68 Kb
Added on: 05-Aug-2005 Downloads: 20
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SIMULATING EFFECTS OF LAND USE CHANGE ON CARBON FLUXES WITH A PROCESS MODEL IN SUBTROPICAL ...
Description:
A process model was used to simulate changes in the carbon fluxes and
stocks at a site that was transformed a grassland to a plantation at Qian
Yanzhou. The total carbon storage of the zonal vegetation (evergreen broadleaf
forest) was simulated and taken as the saturated carbon storage value of that site. The simulated vegetation density and soil organic
carbon (SOC) were compared with the observed. The simulates indicate
that after 20 years planting of the needle leaf forests (Pinus Massoniana, Cunninghamia lanceolata and Pinus elliottii ect) on ex-grassland, the net carbon storage increase in the plantation
was 8.03 kg
C/m2,in which the
vegetation carbon storage increased 8.5334
kg C/m2 and the soil carbon storage decreased 0.518 kg C/m2. The total
carbon storage of 20 years plantation is 58.6%
of the saturated value. The study also shows that between 0 and 7 years of land
use change the soil carbon was decreased and between 7 and 20 years it was
predicted to increase slowly.
Author's Names: M. Huang, J. Ji, M. Cao, and K. Li
Filesize: 51.59 Kb
Added on: 08-Aug-2005 Downloads: 17
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THE IMPACT OF CLOUDS ON ECOSYSTEM CO18O ISOFLUXES IN THE GREAT PLAINS
Description:
Mechanistic
explanations for the downward excursion in d18O of atmospheric CO2
observed during the mid-1990s and the generally large interannnual variability
characteristic of this isotopologue are lacking. We hypothesize that the
excursion and related variations in d18O of atmospheric
CO2 may be linked to global-scale variations in cloud cover.
However, very little is known about the influence of clouds on
biosphere-atmosphere CO18O exchanges. Recent work has demonstrated
the influence of boundary layer clouds on canopy photosynthesis through
increases in the diffuse radiation fraction and relative humidity, combined
with decreases in leaf temperature. In concert, these alterations tend to
increase canopy photosynthesis and conductance, which should also increase CO18O
isofluxes. However, photosynthetic CO18O isofluxes also depend
critically on the d18O of leafwater,
and enhanced cloudiness typically decreases the d18O of leafwater by
enhancing relative humidity and water vapor exchange across stomata. Thus, the net impact of differing cloud regimes on
biosphere-atmosphere CO18O exchanges is difficult to predict.
Preliminary simulations suggest a large impact of diffuse radiation on canopy
photosynthesis by increasing the flux from shade leaves. The impact of this
effect on biosphere-atmosphere CO18O exchanges is diluted somewhat by the lower enrichment in
leafwater d18O on cloudy days
with high diffuse radiation fractions. Our results suggest that these effects
are very dependent on LAI and photosynthetic pathway (C3 or C4).
Author's Names: C.J. Still, W.J. Riley, S.C. Biraud, D. Noone, et al
Filesize: 206.00 Kb
Added on: 08-Aug-2005 Downloads: 122
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