Carbon balance of cultivated soil (loamy Phaeozems) under fallow was compared with that of soils abandoned 1, 5, 10, and 25 years converted naturally to permanent grassland (Moscow region, Russia). Carbon inflow or net primary production (NPP) was calculated as the sum of the above and below ground productivity of grassland ecosystems. The total C outflow was equal to the annual CO₂ fluxes from the soils and was estimated as CO₂ emission measured by the closed chamber method. Carbon balance (CB) was defined as the difference between respiration of heterotrophs and NPP. Botanical survey clearly showed that the vegetation of abandoned agricultural lands changed to permanent grasslands after 5 years of abandonment. Carbon inflow increased from 97 g C·m-2·yr^-1 in the arable soils to 1100 g C·m-2·yr^-1 in the 10-yr grassland. Total annual carbon losses from soils as CO₂ amounted to 347-845 g C·m-2·yr^-1. Heterotrophic respiration varied from 272 g C·m-2·yr^-1 in cultivated soil to 411 g C·m-2·yr^-1 in 25-yr grassland. Our estimations showed that 5, 10, and 25 yr grasslands act as carbon sink and their C balance constituted -217 g C·m-2·yr^-1, -778 g C·m-2·yr^-1 and -473 g C·m-2·y^-1, respectively. Arable soils under the fallow act as CO₂ source (CB = +175 g C·m-2·yr^-1). Carbon balance of the one-year grassland was close to zero. Hence, after 5 years abandonment former arable lands converted to permanent grasslands become a stable C sink.

Pressure fluctuations at the earth’s surface are caused by a variety of atmospheric phenomena. Examples include low frequency barometric pressure variations, high frequency atmospheric turbulence, atmospheric gravity waves, and quasi-static pressure fields created as wind blows over or around topographic features, like buildings, hills, wind breaks, etc. These naturally occurring pressure fields cause air to move in and out of soils, snowpacks, and other permeable media. Consequently, the uptake or release of trace gases from soils and snowpacks is a combination of molecular diffusion and advective flows caused by surface pressure fluctuations. Such pressure forcing has been found to influence the exchange rate of many trace gases from the underlying substrate to the atmosphere. Given the importance of these trace gases to understanding biogeochemical cycling and global change, it is crucial to quantify (as much as possible) any impact these advective flows can have on gas transport within soils and snowpacks. 

We measured components of ecosystem respiration and biomass from wood, foliage and roots in two stands in an old-growth hemlock-northern hardwood forest. Respiration was measured by the chamber method and upscaled to the stand level. Wood production was calculated from the increase in tree size. Foliage biomass was measured from litterfall. Root production was measured from in-growth root cores. Based on the measurements of respiration and biomass we calculated gross primary production (GPP) and net ecosystem production (NEP). The annual GPP was estimated as 1144 and 1089 g C m² y^-1 in the hardwood and hemlock stands, respectively. GPP was partitioned into 131, 115, 270, 168, 257, 203 g C m² y^-1 of wood, foliage, and root respiration, and wood, foliage, and root production, respectively, in the hardwood stand, and 206, 72, 155, 190, 139, 327 g C m² y^-1 of wood, foliage, and root respiration, and wood, foliage, and root production, respectively, in the hemlock stand. The percentage of GPP allocated to wood, foliage and roots for growth and respiration was 20%, 23%, and 57%, respectively, for the hardwood stand, and 31%, 14%, and 55%, respectively, for the hemlock stand. The ratio of net primary production (NPP)/GPP was 30% in the hardwood stand and 33% in the hemlock stand.

We partitioned the components of CO₂ flux by the chamber approaches for a 45-year-old larch forest in northern Japan. In 2003, annual soil-CO₂ efflux was averaged to 9.59 tC ha^-1, heterotrophic respiration was about 5.47 tC ha^-1 that accounted about 57% of the soil-CO₂ efflux, net annual CO₂ exchange of understory vegetation was about -0.39 tC ha^-1, annual aboveground woody tissue respiration was bout 0.75 tC ha^-1, and annual photosynthesis and respiration of the canopy was about -12.75 and 1.15 tC ha^-1, respectively. Annual GPP, NPP, NEP and ecosystem respiration for this forest was estimated to be about 13.49, 7.16, 2.04 and 11.45 tC ha^-1, respectively. The contribution of canopy respiration, aboveground woody respiration, root respiration and heterotrophic respiration to GPP was about 8.1%, 5.6%, 30.6% and 40.5%, respectively.

A Dynamic Global Vegetation Model SEVER [Venevsky, Maksyutov, 2005] was applied for the fourteen EUROFLUX sites [Valentini, 2003] with a large scale daily NCEP climate data as an input (0.5º x 0.5º degree spatial resolution) for years 1997-2000 and net ecosystem exchange (NEE) calculated and observed were compared. Requirements for accurate estimate of local daily NEE flux from a large scale climate data set were found.

We build upon a previous approach to predict C₃ and C₄ fractions on the land surface using new higher resolution satellite datasets on vegetation growth form and crop type coverage. The approach relies upon the near-universal restriction of C₄ photosynthesis to the herbaceous growth form and the differing performance of C₃ and C₄ plants in various temperature and radiation regimes. MODIS-derived data provide detailed information on growth form composition (%herbaceous, %woody, and %bare for each grid cell). Precipitation and temperature variations are derived from station data climatologies. Combining these data with MODIS-derived NPP fields from 2001, we predict latitudinal variations in C3 and C₄ photosynthesis for South America. These variations will be discussed in the context of the global carbon cycle and the difficulty they pose for interannual inversion studies using global CO₂ and d¹³C atmospheric data. 

The magnitude and spatial pattern of the emissions of CO₂, CH₄ and N₂O from China’s terrestrial ecosystems are poorly understood. In this study, we have used a coupled biogeochemistry model in conjunction with remote-sensing and field data to quantify spatial and temporal patterns of CO₂, CH₄ and N₂O fluxes in the terrestrial ecosystems of China since 1980. We have documented the patterns of land-use change across China from 1980 to present and quantified the consequences of land transformations on productivity in natural and managed ecosystems. We also examine how the fluxes of CO₂, CH₄ and N₂O have changed as a result of multiple stresses and interactions among those stresses including land-use change, climate variability, atmospheric composition (carbon dioxide and tropospheric ozone), precipitation chemistry (nitrogen composition), and fire frequency through using factorial simulation experiments with the coupled biogeochemistry model. The estimates of CO₂, CH₄ and N₂O emissions from the terrestrial ecosystems of China are evaluated through comparisons with the results of field studies within China.

Eddy covariance measurements of CO₂ were taken for five years above six forests distributed from the northern to southernmost main islands of Japan. These forests included cool- and warm-temperate deciduous and coniferous forests. The climate of Japan is characterized by apparent seasonal changes and adequate precipitation affected by the East Asian monsoon. In this report, we compared net ecosystem production (NEP) among forests using the eddy covariance method and analyzed the climatic factors that affect seasonal and inter-annual changes in NEP in relation to forest type. The observed annual NEP from 2000 to 2002 ranged from 286 to 566 gCm^-2yr^-1, and this basically increased with decreasing latitude. The observed maximum 10 days mean NEP was about 1.5 times larger in the deciduous sites, although the growing period was more than 2 times longer in the coniferous sites.

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.

A spatially-distributed model of net ecosystem production (NEP) was run over western Oregon for the period 2001-2003 at the 1 km spatial resolution and daily temporal resolution.  Inputs included MODIS-based FPAR, Landsat-based land cover and disturbance history, and distributed meteorology. Resulting NEP showed sensitivity to 1) areas of recent disturbance, such as a large forest fire in 2002, 2) areas of intensive management for timber production, 3) topographically-driven climatic gradients, and 4) interannual variation in climate. Validation measurements included a network of field plots and a chronosequence study.