In this study, soil CO₂ effluxes determined from CO₂ concentration gradients were compared to effluxes obtained with automated chamber measurements. The CO₂ concentrations showed a diurnal pattern following the soil temperature the concentrations increasing with increasing soil depth. Both methods gave comparable CO₂ effluxes indicating that the gradient method provides an alternative method for monitoring soil CO₂ effluxes.

Based on satellite imagery for the 1988s and 2001s, land-use/cover change and associated carbon stock and flux as a result of changes were estimated in Mamlay watershed of Sikkim Himalaya, India. The total area of forest was decreased by 28%, whereas open cropped area increased by more than 100%. The conversion of forests into other land-uses resulted in a remarkable decline in the C densities. Across the land-use/cover, total mean C densities ranged from 46 t ha^-1 in open cropped area temperate to a high of 669 t ha^-1 in temperate natural dense forest. The heavily converted areas lost an estimated 55% of their total 1988 C pools, whereas the low impacted area lost only 0.12%. Changes in land-use released 7.78 tC ha^-1 yr^-1, demonstrating that land-use changes significantly affected C flux. Therefore, the conversion of forest to agriculture land should be reversed.

Forestry and Forest Products Research Institute erected a CO₂ flux observation tower at a Japanese beech forest, and have measured CO₂ flux with closed-pass eddy covariance method for 5 years. During the observation period, 2003 was the most CO₂ absorbed year, and the amount was 1.9 times larger than 2004, which was the least CO₂ absorbed year. To investigate the cause of the smaller CO₂ absorption in 2004, we referred some meteorological factors in 2003 and 2004.  Solar radiation (during green-leaved season) was larger in 2004 than 2003, in contradiction to CO₂ absorption.  On the other, air temperature was higher in 2004 than 2003 (both in green-leaved and defoliated season). We assumed that larger respiration in 2004 effected the depression of annual CO₂ absorption.  At our research site, annual mean air temperature in 2004 was 0.95 degree centigrade warmer than 2003.  The result of this study suggests the tendency that warmer climate may cause less CO₂ absorption in this Japanese beech forest.

The development of agriculture responding to increasing demand for food raises the question of the role of cultivated land in relation to carbon sources and sinks, their spatial patterns and temporal variability.

The influence of nitrogen fertilizing on carbon accumulation and decomposition in arable soils of different fertility – gray forest soil and chernozem was investigated in greenhouse experiment with corn. Growing of plants without N application on rich chernozem favored the considerable (about 1% of С_org) C growth, and on poor gray forest soil contributed to C decrease. Soil organic matter (SOM) decomposition in both soils under unfertilized plants was the same. N usage on gray forest soil resulted in increase of C accumulation due to the substantial increase of C input with roots of fertilized plants and as organic matter active phase of this soil was stable against decomposition under N. N application on chernozem in reverse significantly increased SOM decomposition and affected plant productivity to a lesser degree. Thus, N fertilizing favors C sink in arable soils of low fertility and can reduce soil C accumulation in arable soils of high fertility.

In this paper we briefly introduce our results of soil CO₂ concentrations in an arable field in the campus of NIAES, a grass field and a pine forest in central mountaneous area in Japan.  The soil CO₂ concentrations seasonally variated with soil temperature changes at all the three sites.  Temporal variations in CO₂ concentrations in the arable and the grass field were more linked to changes in soil moisture than those in the forest. Soil CO₂ concentrations were generally largest in the grass field. CO₂ concentrations at the grass field and pine forest under snow cover showed positive relationship with snow depth.

Two major disturbances of forests in western North America are fires and insect outbreaks.  Much research has focused on the effects of fires on the carbon cycle; little research to date has occurred about outbreaks.  We are using observations, including field measurements and remotely sensed imagery, together with ecosystem and insect population modeling improve our understanding of these disturbances on carbon cycling. 

Annual and seasonal dynamics of total soil respiration (TSR) of sandy Albeluvisols and clay Phaeozems under forest, grassland, and arable were studied in situ (Russia, Moscow Region). Measurements of soil CO₂ emission were carried out by closed chamber method from November 1997 through October 2003 weekly. The highest mean TSR (806+86 g C·m^-2·yr^-1) was observed for sandy Albeluvisols under grassland. It significantly exceeded the annual CO₂ fluxes from soils of other ecosystems (P< 0.1). The lowest value of mean annual TSR was observed for arable clay Phaeozems (361+55 g C·m^-2·yr^-1). It was reliably lower than in soils of the other cenoses (P<0.5). No significant differences were found between annual amounts of CO₂ emitted from Albeluvisols under forest and Phaeozems under forest and grassland. The interannual variability of TSR caused by the difference of weather conditions was 30% on average and ranged from 25-26% (forest and grassland ecosystems on Albeluvisols) to 37% (agroecosystem on Phaeozems). We found that TSR in natural ecosystems positively correlated with the total annual precipitation and sum of precipitation for the spring season (R=0.73-0.90, P<0.1). The share of the cold period (November-April) to the annual CO₂ flux was substantial and averaged 22-25% and 17% for natural and agricultural ecosystems, respectively. Therefore, emission of CO₂ during the cold period was an essential part of the annual CO₂ fluxes from soils of sub-boreal zone, which should be taken into account while calculating the carbon budget for the whole year.