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.

Measurements of CO₂ flux were made by the eddy correlation method over a sub-arctic black spruce forest in interior Alaska. Observed CO₂ budget were sinks of -531~-247 and -219~0 g CO₂ m^-2 year^-1 during 2003 and 2004, respectively. The broad range is caused by uncertainty regarding assessment of the nocturnal fluxes. The sequestration of CO₂ during 2004 was limited by high temperature, drought or low light intensity conditions. The net CO₂ flux is in a delicate balance between two large terms, which would shift from sink to source due to global warming.

Model simulations indicated that Canada’s forests and wetlands acted as a carbon (C) sink of 112 Tg C
yr^-1 averaged during 1901-1998. Wetlands was a crucial contributor to this sink (50 Tg C yr^-1). Disturbance history determined the decadal temporal pattern of C balance. Nondisturbance factors enhanced C accumulations in Canada’s forests and wetlands in the last century. The enhancement of each nondisturbance factor on C uptake changed temporally.

A process model was used to simulate changes in the carbon fluxes and stocks at a site that was transformed a grassland to a plantation at Qian Yanzhou. The total carbon storage of the zonal vegetation (evergreen broadleaf forest) was simulated and taken as the saturated carbon storage value of that site. The simulated vegetation density and soil organic carbon (SOC) were compared with the observed. The simulates indicate that after 20 years planting of the needle leaf forests (Pinus Massoniana, Cunninghamia lanceolata and Pinus elliottii ect) on ex-grassland, the net carbon storage increase in the plantation was 8.03 kg C/m²，in which the vegetation carbon storage increased 8.5334 kg C/m² and the soil carbon storage decreased 0.518 kg C/m². The total carbon storage of 20 years plantation is 58.6％ of the saturated value. The study also shows that between 0 and 7 years of land use change the soil carbon was decreased and between 7 and 20 years it was predicted to increase slowly.