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A Guide to Information on Greenhouse Gases and Ozone Depletion
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FROM VOLUME 9, NUMBER 2, FEBRUARY 1996

PROFESSIONAL PUBLICATIONS...
CARBON CYCLE

Item #d96feb25

"Increased Biological Productivity and Export Production in the Glacial Southern Ocean," N. Kumar (Sch. Intl. & Public Affairs, Columbia Univ., New York NY 10027), R.F. Anderson et al., Nature, 378(6558), 675-680, Dec. 14, 1995.

The results of this study bear on the recent suggestion that atmospheric CO₂ levels could be reduced by deliberately stimulating biological activity in certain ocean regions by adding iron. Examination of radionuclides in marine sediments shows that during glacial periods over the past 140,000 years, biological productivity in the Southern Ocean was associated with an increased supply of iron to surface waters, carried by winds from the Patagonian deserts.

Item #d96feb26

Three items from Global Biogeochem. Cycles, 9(4), Dec. 1995:

"Terrigenous Fe Input and Biogenic Sedimentation in the Glacial and Interglacial Equatorial Pacific Ocean," R.W. Murray (Dept. Earth Sci., Boston Univ., Boston MA 02215), M. Leinen et al., 667-684. Examines the role of terrigenous iron input in regulating atmospheric CO₂ levels, by analyzing sediment cores that record deposition through the last six glacial cycles (~600,000 years). Overall, results show no relationship between terrigenous iron input and sedimentary sequestering of carbon in this region of the ocean.

"Toward a Global Estimate of Black Carbon in Residues of Vegetation Fires Representing a Sink of Atmospheric CO₂ and a Source of O2," T.A.J. Kuhlbusch (US EPA, 960 College Sta. Rd., Athens GA 30605), P.J. Crutzen, 491-501. Black carbon produced in fires is very resistant to microbial decay and may represent a substantial carbon sink. This study arrives at estimates of black carbon production from various types of biomass fires, based on laboratory experiments. Results show that carbon sequestration in this form reduces estimates of net carbon flux due to changes in land use by up to 25%.

"On the Contribution of CO₂ Fertilization to the Missing Biospheric Sink," D. Friedlingstein (NASA Goddard Inst. Space Studies, 2880 Broadway, New York NY 10025), I. Fung et al., 541-556. Estimates the biospheric contribution to the carbon cycle over the industrial period using a global biospheric model, which is much more comprehensive than the type of model previously applied to the problem. Results suggest that about two thirds to three fourths of the 1850-1990 integrated missing carbon sink is due to the CO₂ greening of the biosphere. The remainder may be due to the increased level of nitrogen deposition starting around 1950.

Item #d96feb27

"Gas Diffusivity and Production of CO₂ in Deep Soils of the Eastern Amazon," E.A. Davidson (Woods Hole Res. Ctr., POB 296, Woods Hole MA 02543), S.E. Trumbore, Tellus, 47B(5), 550-565, Nov. 1995.

Estimates show that 20-30% of CO₂ flux from the soil surface is produced below a depth of one meter by root respiration and microbial decay, indicating that deep-soil processes are a significant component of carbon cycling in these deep-rooted ecosystems. About 1% of the stock of soil carbon found in the 1-8 meter layer turns over annually; land-use changes that affect rooting depth could significantly affect deep soil carbon stocks over decades to centuries.

Item #d96feb28

"Carbon Dioxide Uptake by an Undisturbed Tropical Rain Forest in Southwest Amazonia, 1992 to 1993," J. Grace (Inst. Ecology, Univ. Edinburgh, Edinburgh EH9 3JU, UK), J. Lloyd et al. Science, 270(5237), 778-780, Nov. 3, 1995.

Previous studies suggest that the terrestrial biosphere may be undergoing fertilization as a result of increasing concentrations of CO₂ combined with higher deposition of nitrogen. Extended measurements of CO₂ flux over an undisturbed tropical rain forest presented here lead to an estimate of net carbon absorption by the ecosystem of 8.5 moles per square meter per year.

Item #d96feb29

"Carbon Balance in the Tundra, Boreal Forest and Humid Tropical Forest During Climate Change: Scaling up from Leaf Physiology and Soil Carbon Dynamics," Y.P. Wang (Div. Atmos. Sci., CSIRO, P.B. 1, Mordialloc, Victoria 3195, Australia), P.J. Polglase, Plant, Cell, Environ., 18(10), 1226-1244, Oct. 1995.

Calculations based on a general model of ecosystem carbon fluxes show that, several times during the past 140 years, tundra and boreal forest biomes have alternately been carbon sources and carbon sinks. More recently, high latitude warming during 1988 and 1990 caused tundra and boreal forests to be net sources. Humid tropical forests have generally been a carbon sink since 1960. Under projected CO₂ and temperature increases, the tundra and boreal forests will emit increasingly more carbon, while the humid tropical forests will continue to store carbon.

Item #d96feb30

"Land Use Change and the Carbon Cycle," R.A. Houghton (Woods Hole Res. Ctr., POB 296, Woods Hole MA 02543), Global Change Biol., 1(4), 275-287, Aug. 1995.

A commissioned review. Compares various estimates of net carbon flux between land and the atmosphere, showing that much of the variability results from differences in approach. If evaluated carefully, these differences may help increase our understanding of the net carbon balance in terrestrial ecosystems.

Item #d96feb31

"Soil and Biomass Carbon Pools in Model Communities of Tropical Plants Under Elevated CO₂," J.A. Arnone III (Dept. Botany, Univ. Basel, Sch?nbeinstr. 6, CH-4056 Basel, Switz), Ch. K?rner, Oecologia, 104(1), 61-71, 1995.

Reports experiments conducted in greenhouses with somewhat nutrient-limited model communities of moist tropical plant species. Finds that: enormous amounts of carbon can be deposited in the ground that are not normally accounted for in estimates of net primary productivity and net ecosystem productivity; any enhancement of carbon sequestration under elevated CO₂ may be substantially smaller than is currently believed; species dominance in plant communities is likely to change under elevated CO₂, but changes may be slow.

Item #d96feb32

"Role of Russian Forests in the Global Carbon Balance," T.P. Kolchugina (Dept. Civil Eng., Oregon State Univ., Corvallis OR 97331), T.S. Vinson, Ambio, 24(5), 258-264, Aug. 1995.

The absence of a common approach to quantifying terrestrial carbon has resulted in substantial discrepancies in regional, national and global estimates. One of the most dramatic examples is flux estimates for Russian forests, which differ by two orders of magnitude. This paper presents a comprehensive system of accounting which shows that the sequestration of carbon in Russian forests is substantial, about 0.66 Pg carbon per year in the late 1980s and early 1990s. About a third this amount was returned to the atmosphere through logging and forest fires.

Item #d96feb33

Two related items in Nature, 376(6543), Aug. 31, 1995:

"Is the Ocean Losing Nitrate?" L.A. Codispoti (Ctr. Coastal Phys. Oceanog., Old Dominion Univ., Norfolk VA 23529), 724. Discusses how the following paper adds to the evidence that the present-day ocean is losing fixed nitrogen, which implies lower plant productivity and lower oceanic uptake of CO₂. Increased denitrification could result if schemes to fertilize the ocean with trace metals led to an increased flux of organic material to deep layers.

"Large Changes in Oceanic Nutrient Inventories from Glacial to Interglacial Periods," R.S. Ganeshram (Dept. Oceanog., Univ. British Columbia, Vancouver BC V6T 1Z4, Can.), T.F. Pedersen et al, 755-758. Nitrate is an oceanic nutrient that can be regulated by changes in the rate at which it is degraded by bacteria (denitrification) in oxygen-deficient subsurface waters. Nitrogen isotope ratios in marine sediment cores taken from the eastern tropical North Pacific Ocean show that water-column denitrification was greatly diminished during glacial periods. A consequent increase in the oceanic nitrate inventory could have contributed to the well-documented decrease in atmospheric CO₂ during glacial periods.

Item #d96feb34

"Diurnal Changes in the Partial Pressure of Carbon Dioxide in Coral Reef Water," H. Kayanne (Dept. Geog., Univ. Tokyo, Hongo, Tokyo 113, Japan), A. Suzuki, H. Saito, Science, 269(5221), 214-216, July 14, 1995.

Coral reefs are considered to be a source of atmospheric CO₂ because of their high calcium carbonate production and low net primary production. However, direct measurements of partial pressure on a Japanese island reef show that the reef flat area is a net sink for CO₂, suggesting that the net organic production exceeded net calcium carbonate production during the observation periods.

Item #d96feb35

Two items from Chemosphere, 29(5), Sep. 1994:

"Prehistoric Anthropogenic Wildland Burning by Hunter-Gatherer Societies in the Temperate Regions: A Net Source, Sink or Neutral To the Global Carbon Budget?" M.K. Anderson (Hall Ctr. for Humanities, Univ. Kansas, Lawrence KS 66045), 913-934. Demonstrates the need for more intense multi-disciplinary study of prehistoric "hunter-gatherer" burning patterns in temperate regions, using California as an example. Presents an approach for better defining patterns of anthropogenic wildland burning in various regions of North America at the time of Euro-American contact. Physical, social and biological scientists should work together to examine global warming in a broader historical context to explore this question, which has profound implications for global warming mitigation policies.

"Biomass Utilization in Households and Industry: Energy Use and Development," D.O. Hall (Div. Life Sci., King's Coll., London W8 7AH, UK), F. Rosillo-Calle, J. Woods, 1099-1119. The historical importance of biomass-related carbon releases through human activities is increasingly recognized, but the available data are insufficient for full evaluation. This paper re-examines the role of past and present biomass energy use (including its relation to population and environment), and potential anthropogenic carbon releases from biomass, with particular attention to land use changes, biomass burning, and industrial uses.