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
Filesize: 50.76 Kb
Added on: 29-Jul-2005 Downloads: 145
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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
Added on: 04-Aug-2005 Downloads: 21
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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
Filesize: 112.58 Kb
Added on: 02-Aug-2005 Downloads: 20
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INTEGRATION OF EXISTING DATA TO ESTIMATE THE INFLUENCE OF SOIL AND WATER MANAGEMENT ON CARBON ...
Description: Human
activities have altered rates of carbon erosion from soils and carbon
deposition in sediments. We are
developing methods to quantify the present-day and historical effects of these
changes on the carbon mass balance of the conterminous U.S. land surface. Because our analysis uses a combination of
diverse existing datasets, we devote particular attention to methods for the
estimation of uncertainties that are consistent with the statistical character
of the source data.
Author's Names: Eric T. Sundquist, Katherine Visser Ackerman, et al
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Added on: 08-Aug-2005 Downloads: 111
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INTENSIVE TILLAGE AS A MECHANISM FOR CO2 EMISSION FROM AGRICULTURAL SOILS
Description: Agricultural ecosystems can play a significant
role in production and consumption of greenhouse gases, specifically, carbon
dioxide (CO2). Information is
needed on the mechanism and magnitude of gas generation and emission from
agricultural soils with specific emphasis on tillage mechanisms. This work
reviews effect of different tillage methods on the short-term CO2
and H2O vapor flux from clay loam soils high in soil organic carbon
(C) in the northern corn belt of the U.S. [Reicosky
and Lindstrom, 1993, 1995; Reicosky,
1997, 1998]. The soil CO2 flux was measured one minute after the
tillage using a large, portable chamber as described by Reicosky and Lindstrom [1993]. The four tillage methods were
moldboard plow (MP) only, moldboard plow plus disk harrow twice, disk harrow
and chisel plow using standard tillage equipment following a wheat (T. Aestivum
L) crop compared with no tillage (NT).
Author's Names: D.C. Reicosky
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Added on: 03-Aug-2005 Downloads: 21
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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
Filesize: 93.13 Kb
Added on: 01-Aug-2005 Downloads: 21
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INTERANNUAL VARIABILITY IN TERRESTRIAL CARBON EXCHANGE USING AN ECOSYSTEM FIRE MODEL
Description: We have incorporated a
semi-mechanistic fire model into the SEVER Dynamic Global Vegetation Model (DGVM).
The model produces estimates of net primary productivity (NPP), heterotrophic
respiration (HR) and fire carbon emission (FE) for the globe. This model was
run for the period 1957-2002 with the NCEP climate reanalysis data as an input.
Results were compared with the ATSR area burnt maps and a Time Dependent
Inverse (TDI) model fluxes of CO2. We find that on interannual time
scales NPP variability explains major part of flux variability simulated by the
TDI model, followed by the HR and FE contributions.
Author's Names: Sergey Venevsky, Prabir K. Patra, Shamil Maksyutov, et al
Filesize: 64.05 Kb
Added on: 08-Aug-2005 Downloads: 162
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INVESTIGATIONS OF THE LAND BIOTIC O2:CO2 EXCHANGE RATIOS IN PHOTOSYNTHESIS AND RESPIRATION
Description:
Accurate estimations of the
land biotic O2/CO2 exchange ratios are required to allow
quantification of the land/ocean carbon sink partitioning from atmospheric
measurements of both O2 and CO2 concentrations.
This study shows atmospheric
O2 and CO2 mixing ratios as well as their diurnal cycles
over a three day period in May 2005 from flask samples collected at 3 different
heights (1, 4 and 12m) in an undisturbed
forest in central Germany. An average O2/CO2 ratio of
0.99 was estimated with very little variation between the three different
heights. In addition, the “night time” average value of atmospheric O2/CO2
ratio did not show any significant difference from the average “daytime” value.
Author's Names: E. Kozlova, A.C. Manning, A. Jordan and W. Brand
Filesize: 40.34 Kb
Added on: 01-Aug-2005 Downloads: 23
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LAND-USE COVER CHANGE AND CARBON FLUX IN A HIMALAYAN WATERSHED
Description: Based
on satellite imagery for the 1988s and 2001s, land-use/cover change and
associated carbon stock and flux as a result of changes were estimated in
Mamlay watershed of Sikkim Himalaya, India. The total area of forest was
decreased by 28%, whereas open cropped area increased by more than 100%. The
conversion of forests into other land-uses resulted in a remarkable decline in
the C densities. Across the land-use/cover, total mean C densities ranged from
46 t ha-1 in open cropped area temperate to a high of 669 t ha-1
in temperate natural dense forest. The heavily converted areas lost an
estimated 55% of their total 1988 C pools, whereas the low impacted area lost
only 0.12%. Changes in land-use released 7.78 tC ha-1 yr-1,
demonstrating that land-use changes significantly affected C flux. Therefore,
the conversion of forest to agriculture land should be reversed.
Author's Names: Purnima Sharma, and S.C. Rai
Filesize: 28.59 Kb
Added on: 03-Aug-2005 Downloads: 20
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LEAF AND BRANCH PRODUCTIVITY OF SEVERAL PLANT COMMUNITIES OF NORTHEASTERN MEXICO
Description:
Leaf
and branch biomass productivity of plant communities have been little studied in
northern Mexico.
Global warming concerns are prompting research dealing with biomass production
and carbon sequestration by plant communities. Biomass components and
productivity are key pieces of information for running several carbon models.
In this research, we developed information on leaf and branch biomass productivity
of sixteen different plant communities encompassing native pine, oak, shrub,
and exotic pine forests. We established sampling plots, measured dasometric
features of trees, and collected leaf and branch biomass for periods of 7 to 21
days during 2004 in Nuevo Leon, Mexico. Results indicate that leaf and branch
productivity is on the average 3.70 Mg ha-1 y-1 (±0.98 Mg
ha-1 y-1) with only two plant communities (intermittent
riverine Tamaulipan matorral and upland planted Cupressus spp communities)
surpassing 7 Mg ha-1 y-1. The exotic pine species (P. nelsoni, P. pinceana, and P.
cembroides) planted in proceeding trials produced less than 3 Mg ha-1
y-1. The statistical analysis of this information showed large spatial
and temporal variations. The former was explained by microsite and plant
density. The last source of variation was partially dependent on climate
fluctuations and the natural annual productivity cycle. Further research is
required to understand the fate of leaf and branch on soils.
Author's Names: J. Návar1, and O.L. López
Filesize: 93.44 Kb
Added on: 03-Aug-2005 Downloads: 22
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