Sink For Atmospheric Carbon Research Articles

The Carbon Budget of the Canadian Forest Sector: Phase I

An assessment of the contribution of Canadian forest ecosystems and forestry activities to the global carbon budget has been undertaken. The first phase of this study consisted of the development of a computer modeling framework and the use of pub lished information to establish the sector's current role as a net source or a net sink of atmospheric carbon. The framework includes age-dependent carbon sequestration by living forest biomass, net detrital litter fall of carbon to the forest floor, subsequent accumulation and decomposition release in three soil compartments, retention of carbon in manufactured products derived from harvested forest biomass, and burning of forest biomass for energy. There is explicit representation of the role of ecosystem disturbances, such as fire, insect-induced stand mortality, and harvesting (clear-cutting, clear- cutting and slash burning, and partial cutting), as they affect carbon releases and transfers to the forest floor and to the forest product sector. Regrowth of biomass and changes in soil decomposition processes following disturbance are also simulated within the model. In the first phase of the work, national and provin cial data bases were used to provide the first compre hensive estimates of the net carbon exchange between Canadian forest ecosystems and the atmosphere for the reference year 1986.

Potential effect of no-till management on carbon in the agricultural soils of the former Soviet Union

Agricultural soils act as both a source and a sink for atmospheric carbon. Since the onset of cultivation, the 211.5 million ha of agricultural soils in the former Soviet Union (FSU) have lost 10.2 Gt of carbon. No-till management represents a promising option to increase the amount of carbon sequestered in the agricultural soil of the FSU. No-till management reduces erosion and sequesters additional carbon in the soil by lowering the soil temperature and raising soil moisture. To determine the carbon sequestered under no-till management, a data base containing precultivation estimates of soil carbon for the seven major classes of soil found in the agricultural areas of the FSU was used to establish an equilibrium carbon content for each soil. Other published data provided a method to quantify the change in soil carbon brought about by converting to no-till management. Soils suitable for no-till management were analyzed and estimates of changes in carbon storage were made. No-till management is not suitable in areas where crop production is limited by cold, wet soils. Based on the results of a geographic information system analysis using maps of climatic factors and soil characteristics, 181 million ha in the FSU were identified as climatically suitable for no-till management (almost 86% of all agricultural land). Complete conversion of all climatically suitable land to no-till management would sequester 3.3 Gt of carbon. This represents a 10% increase in carbon in the agricultural soils of the FSU. This estimated accumulation of carbon is associated with a new soil carbon equilibrium condition. Accumulation of carbon in the soil produced by a conversion from conventional to no-till management is expected to take at least 10 years. The carbon accumulation produced by conversion to no-till management is not a continuing process; once a new no-till equilibrium condition has been reached, additional quantities of atmospheric carbon will not be sequestered in agricultural soils through continued no-till management.

Tropical forests as sinks of atmospheric carbon

Changes in land use and rates of carbon accumulation by land use including mature, logged, and fallow tropical forests, and degraded tropical lands are used to estimate the role that the tropical landscape serves as sinks of atmospheric carbon. Results indicate that in 1980 tropical lands may remove between 1.5 and 3.2 Pg C from the atmosphere. We excluded from the analysis some 900 million ha of open tropical forests that could also be removing carbon from the atmosphere and an additional 0.5–0.6 Pg C year−1 sink associated with carbon export by rivers and in wood products. Our analysis challenges assumptions about the steady-state condition of the carbon budget of mature tropical forests and suggests that large areas of the tropical landscape are recovering from disturbance and act as atmospheric carbon sinks. We focus attention on sinks of atmospheric carbon only. In 1980, the estimated accumulation of carbon in the recovering landscape was equal to the net carbon flux due to tropical deforestation.

Comments on the role of oceanic biota as a sink for anthropogenic CO2 emissions

In a letter published in Issues in Science and Technology, Revelle [1990] comments that one of the principal sinks for atmospheric carbon is probably phytoplankton production in the ocean. Revellegoes on to state (p. 21‐22).This process (that of phytoplankton growth and death, followed by settling of organic carbon out of the surface ocean to depth; the so‐called “biological pump”) could account for the sequestration of at least a billion tons of carbon of the total of five billion or six billion produced annually by fossil fuel consumption and biological activity.

Atmospheric Carbon Particles in the Detroit Urban Area: Wintertime Sources and Sinks

The sources and sinks of organic carbon (OC) and elemental carbon (EC) were studied in the Detroit area during the 1983–1984 and 1984–1985 winters. Based on fuel usage and emission estimates, the largest carbon source was residential wood burning, which contributed 60% of OC emissions and 49% of EC emissions. Diesel vehicles contributed another 6% of OC emissions and 2% of EC emissions. Commercial and residential coal burning also contributed 27% of OC and 13% of EC. The sinks of atmospheric carbon were determined by measuring the carbon content of atmospheric particles, wet deposition and dry deposition. Carbon levels in air particles averaged 5.6 μg/m3 OC and 2.2 μg/m3 EC. Precipitation concentrations averaged 760 μg/L OC and 160 μg/L EC. The OC/EC ratio was higher in precipitation (4.7) than in ambient particles (2.5), indicating that a high OC/EC ratio increases the hygroscopicity of the particles, and hence, their removal by precipitation. Based on the known oxidation rate, insufficient EC is availab...

Wintertime concentrations and sinks of atmospheric particulate carbon at a rural location in Northern Michigan

Particulate elemental carbon, organic carbon, and SO 2− 4 wintertime atmospheric concentrations were determined at a rural site in northern Michigan during two winters. Examination of the concentrations, based on both surface-wind direction and backward-trajectory analysis, indicated that concentrations were significantly influenced by the long-range transport of pollutants. Measurements of the wet- and drydeposition rates of elemental carbon showed that it is removed primarily by wet deposition at this site. The dry deposition velocity of elemental carbon to a snow surface averaged <0.2 cm s −1 during most of the study, but was considerably higher for one period during which it appeared to be influenced by large particles from local sources. A comparison of the scavenging ratios of SO 2− 4 and elemental carbon shows that snow removes SO 2− 4 at least twice as efficiently as elemental carbon. This difference implies that the atmospheric residence time of elemental carbon in the winter will be considerably longer than that of SO 2− 4, if precipitation occurs. In the absence of precipitation, the estimated residence time of elemental carbon is at least 6 days. These results suggest that elemental carbon can be transported long distances and, thus, may degrade visibility and have other effects over wide regions.

Biomass of tropical tree plantations and its implications for the global carbon budget

To determine the present and future role of tropical tree plantations in the global carbon budget, data on rates of plantation establishment and their commercial volumes, by species groups and age-classes, were gathered and converted to biomass and ultimately to carbon fluxes. The rate of plantation establishment has increased dramatically since the 1940's, resulting in an area in 1980 of about 11 × 106 ha with more than 60% of this area planted during the last decade. Total biomass of plantations is estimated to range from 0.65 × 109 to 2.22 × 109 t or about 1% of the biomass of natural forests. Most of the biomass (79%) is in the 6- to 30-year-old plantations. We estimate that tropical plantations are a small sink of atmospheric carbon of 0.03–0.11 × 109 t C/year, most of which occurs in the two youngest age-classes. Although this flux is small, it may be sufficient to balance the small source of carbon from harvesting forests and other land-use changes in the temperate zone.