We report measurements of energy and carbon fluxes from a boreal forest fire chronosequence. Taking into account greenhouse gas emissions and post-fire changes in the surface radiation budget, a boreal forest fire in interior Alaska caused the climate to cool. This result suggests that management of forests in northern countries to preserve carbon sinks may have the opposite effect on climate as that intended.

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.

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.

Soil respiration is derived from heterotrophic (decomposition of soil organic matter) and autotrophic (root/rhizosphere respiration) sources, but there is considerable uncertainty about what factors control variations in their relative contributions in space and time. We took advantage of a unique whole-ecosystem radiocarbon label in a temperate forest to partition soil respiration into three sources: (1) recently photosynthesized carbon (C), which dominates root and rhizosphere respiration; (2) leaf litter decomposition and (3) decomposition of root litter and soil organic matter >1-2 years old. Heterotrophic sources and specifically leaf litter decomposition were large contributors to total soil respiration during the growing season. Relative contributions from leaf litter decomposition ranged from a low of ~1 ±3% of total soil respiration (6 ±3 mg C m^-2 hr^-1) when leaf litter was extremely dry, to a high of 42 ±16% (96 ±38 mg C m^-2 hr^-1). Total soil respiration fluxes varied with the strength of the leaf litter decomposition source, indicating that moisture-dependent changes in litter decomposition drive variability in total soil respiration fluxes. Root/rhizosphere respiration accounted for 16 ±10% to 64 ±22% of total soil respiration, with highest relative contributions coinciding with low overall soil respiration fluxes. In contrast to leaf litter decomposition, root respiration fluxes did not exhibit marked temporal variation ranging from 34 ±14 to 40 ±16 mg C m^-2 hr^-1 at different times in the growing season with a single exception (88 ±35 mg C m^-2 hr^-1). Radiocarbon signatures of root respired CO₂ changed markedly between early and late spring (March vs. May), suggesting a switch from stored nonstructural carbohydrate sources to more recent photosynthetic products.

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.

A land surface model (Biosphere-Atmosphere Interaction Model Ver.2: BAIM2) can estimate not only the energy fluxes, but also the carbon dioxide flux between terrestrial ecosystems and the atmosphere. The photosynthesis processes for C₃ and C₄ plants are adopted in the model. The carbon storage of vegetation is divided into five components (leaves, trunk, root, litter, and soil), and the carbon exchanges among the components of vegetation and the atmosphere are estimated in each time step of the on-line model integration. The values of morphological parameters using in the model are derived from the carbon storage values of the components, and the phenological changes of vegetation are reproduced by the model. The BAIM2 was incorporated into a spectral general circulation model, and was connected on-line to the atmospheric model. Using this climate model, an experimental control time integration was performed under the actual global vegetation condition. After the control time integration, the vegetation types of Southeast Asia were changed to the C₄ grass, and the vegetation change impact integration was performed. The results of the impact experiment were compared with the results of the control. In the Indochina Peninsula area, by the vegetation change from the tropical seasonal forest to the C₄ grass, year mean values of the NPP generally increased, and those of the NEP also increased. On the other hand, in the maritime continent area, by the change from the tropical rain forest to the C₄ grass, the NPP values generally decreased, and the NEP values also decreased. It was considered that the differences of phenological changes of vegetation in these areas and the differences of climatic impact of vegetation changes induced the different change phenomena of the carbon cycles. There is a possibility that the influences of the vegetation changes (deforestation) on the carbon cycles are different in the area where the original vegetation types are different.

The present research is an attempt to examine and investigate the impact of land use land cover changes on the environmental sustainability and livelihood security of the local community in the Upper Kullu Valley of the Western Himalaya. Research is based on both the primary as well as secondary data sources. For the primary data were collected through Direct Field Investigation Technique (DFIT) based on Stratified Random Sampling (SRS) Technique. The secondary data were colleted from various Governmental as well nongovernmental offices working in the field of Himalayan environment and sustainability.

Measurements of net ecosystem CO₂ exchange using continental tower flux networks provide a critical constraint in models of regional and global carbon budgets. Uncertainty exists in these measurements due to the effects of complex terrain and vegetation gradients. Using an array of seven towers distributed across a mountain landscape, we estimated that a significant error exists in the five-year record of measured net ecosystem CO₂ exchange. The error was due to the previously ignored influence of advective CO₂ fluxes. When this error was rectified by explicit consideration of the advective flux components, the forest was predicted to exhibit a 38% higher potential for carbon sequestration than previously thought.

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.