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.

The objective of this study is to provide improved estimation of the area extent for major mire types within West Siberia (WS) and determine the spatial variability of NPP and biomass in relation to macro/micro landscape and site position within the bioclimatic division. Our approach relies upon scaling up available field survey and literature data to provide wetland net primary production (NPP) and biomass inventory maps for West Siberia. Both, satellite images and aerial photography classifications have been used to extrapolate site data into a regional inventory map (1:2.5M scale). Total NPP of wetlands is estimated as 530.5 TgDM (teragram/megaton dry matter)yr^-1, or 624.4 TgDM/yr when woody parts are included. Lowest NPP has been assigned to wetlands at the northern part of Taiga zone (4.5-6.2 tonDM)/ha/yr^-1). Wetlands in Tundra, Forested tundra and southern parts of Taiga zone show considerably higher NPP values. Minimum of living biomass storage was found in middle and southern taiga subzones. It is also increased to the north and south within West Siberian territory.

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.

There remain large uncertainties in our model estimations of terrestrial CO₂ budget at broad scales. We used two terrestrial carbon cycle models (Sim-CYCLE and SASAI) and three climate datasets (NCEP/NCAR, NCEP/DOE, and ERA40) for the period from 1982 to 2001 and performed cross-comparison, aiming at clarifying the source of uncertainties. Using the same model, different carbon budgets were obtained by the three climate datasets, globally due to the difference in solar radiation and locally due to precipitation. The two models, which differ in canopy processes, estimated different temporal trends and spatial patterns of CO₂ budget during the experimental period. This study exemplified the necessity of developments in both models and datasets.

In a temperate deciduous forest in Japan situated complex terrain, net ecosystem CO₂ exchange (NEE) was estimated using micro-meteorological method, and net ecosystem products (NEP) was estimated by measures of major carbon pools and fluxes using biometric and chamber methods. In this study we evaluate the threshold value of u* for interpolation in case stability was high using estimated NEP acquired by biometric method. And the function which relate temperature to FCO₂ for interpolation was evaluated by the data acquired using automated chamber for soil, CWD, trunk and foliage CO₂ exchanges. Averaged net uptake of CO₂ measured by eddy covariance method from 1999 to 2002 was 3.4 tC yr^-1 ha^-1 without compensation of nighttime underreport. Increase of live under and above ground biomass from 1994 to 1999 was 1.56 tC yr^-1 ha^-1. U* threshold values based on biometric and chamber NEP were respectively 0.28 and 0.35 m sec^-1

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.

For more than 1000 years, the forests in mountainous areas of Japan have been distinguished by excessive harvesting and litter collection. Revegetation of these areas over the past 130 years has resulted in the current forest coverage. However, the forest soils are immature and contain very little organic carbon. Therefore, the past human impact likely affects the present carbon cycle and CO₂ efflux at the forest floor. It is important to estimate the carbon cycle and CO₂ efflux at the forest floor in such a heavily affected ecosystem to discuss the relationship between the carbon cycle and land use management. Therefore, we measured the CO₂ efflux at the forest floor in a deciduous forest heavily affected by human activities in Japan and estimated the annual rate.

Terrestrial ecosystems are major sources and sinks of carbon. Quantifying their role in the continental carbon budget requires an understanding of both fast (hours to days) and longer-term fluxes (years to decades). The Intercontinental Chemical Transport Experiment-North America (INTEX-NA) is a major NASA science campaign designed to understand the transport and transformation of gases and aerosols on transcontinental and intercontinental scales and their impact on air quality and climate. During the INTEX-NA summer 2004 phase, regional-scale in-situ measurements of atmospheric CO₂ were made from the NASA DC-8 over the conterminous U.S. affording the opportunity to explore how land surface heterogeneity relates to the airborne observations utilizing remote-sensing data products and GIS-based methods. In this presentation, several derived products from the LANDSAT, NOAA AVHRR, and MODIS sensors are invoked to specify spatiotemporal patterns of land use cover and vegetation characteristics for linking the aircraft-based CO₂ data with terrestrial sources of carbon. In examining the landscape mosaic utilizing these available tools, preliminary results suggest that the lowest CO₂ mixing ratios observed during the mission were over agricultural fields in IL dominated by corn then secondarily soybean crops. Low CO₂ concentrations are attributable to sampling during the peak growing season over such C4 plants as corn having a higher photosynthetic rate via the C4-dicarboxylic acid pathway of carbon fixation compared to C3 plants such as soybeans. In addition to LANDSAT derived biophysical products, results from comparisons of the CO₂ observations with NDVI values derived from MODIS data will be presented.

To evaluate the role of root respiration (Rr), we measured spatial and temporal variation of Rr. We measured root biomass, Rr and soil respiration (Rs) in temperature deciduous forest in central Japan. The size dependence of Rr was shown and Rr in fine root (< 2 mm) accounted more than half of total Rr per unit area. Moreover, we had measured continuously Rr and Rs using automated system. Rr responded exponentially to soil temperature. High soil moisture during and just after rainfall caused limiting factor in Rr. And the contribution of Rr to Rs changed seasonally.