To properly model carbon (C) sequestration capacity and its spatial pattern in the conterminous USA, the model parameters of C turnover times should be identified. In this study, we inversed the C turnover times based on a process-based model that combining Carnegie-Ames-Stanford Approach (CASA model) and vegetation and soil carbon transfer (VAST) model. The genetic algorithm was used in this study to search for optimal parameters of C turnover times. After inversing the spatial pattern of C turnover times, we modeled the carbon sequestration capacity by using a forward model under current NPP increase trend that derived from satellite data.

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.

Understanding the geographical distribution of carbon uptake by the terrestrial biosphere is critical for predicting future trends of atmospheric CO₂.  With inverse techniques, atmospheric CO₂ measurements can be used to estimate this uptake. The results from this approach, however, depend on the accuracy of the transport model(s).  Because of the covariance between the seasonally-varying biosphere exchange and the strength of vertical mixing (the rectifier effect), using only the surface CO₂ observations for this analysis yields an inferred carbon flux that is highly sensitive to the details of the boundary-layer dynamics in the transport model [Gurney et al., 2004]. One possible way to reduce the sensitivity of these inversions to poorly-represented boundary-layer dynamics is to use CO₂ vertical profiles (and/or column CO₂ measurements) in addition to surface observations. In theory, multi-level aircraft CO₂ measurements from several well-positioned sites are capable of improving the estimate of the true annual mean inter-hemisphere CO₂ gradient and thereby improving the estimate of the partitioning of carbon sinks between the two hemispheres.

We evaluated the current status and the future projection of soil organic carbon (SOC) storage in Japanese croplands (paddy and upland), using a soil carbon turnover model. The model based on the RothC involves the modification after verification of turnover processes of SOC for the main soil type in Japan, Andosols. The objectives of this study are to i) evaluate the spatial distribution of SOC storage, ii) estimate the annual input organic matter for reaching the equilibrium, and iii) simulate time changes of SOC storage with changing agricultural practices as well as climate conditions.

Terrestrial carbon fluxes are an important factor for the studies of global warming. This study focuses on estimating a fluctuation of the terrestrial carbon fluxes in the Tokai region, Japan. The local biosphere model used calculates carbon, water, and heat fluxes, and required some climate and vegetation parameters as inputs. The model was operated in 2000-2004 using meteorological data and MODIS data products. We estimated spatial distributions in heat and carbon fluxes at spatial resolution of 1*1 km, and validated an adaptability of the model using measured data at the Takayama flux-site. As a result, estimated GPP and heat fluxes had a good relationship to measured data. We can precisely check on the accuracy of the model to estimate the spatial and temporal patterns of the terrestrial carbon fluxes.

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.

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.

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.

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, 46^o57'N, 16^o39'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.

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.