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.

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.

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 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 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.