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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 12, NUMBER 3, MARCH 1999

JOURNAL ARTICLES...
SOIL EMISSIONS

Item #d99mar5

“Diurnal and Seasonal Variation of Carbon Dioxide Exchange from a Former True Raised Bog,” J. P. Nieveen, C. M. J. Jacobs, and A. F. G. Jacobs,Global Change Biology 4 (8), 823-833 (1998).

A shallow peat layer overlain with vegetation (largely Molinia caerulea) released 97 g C/m2-y to the atmosphere. Uptake outpaced release during June, July, and August, only. Leaf area index and temperature were the determining factors for net exchange of CO₂; temperature was the controlling factor of soil respiration.

Item #d99mar6

“Model Estimates of Methane Emission from Irrigated Rice Cultivation of China,” Yao Huang, R. L. Sass, and F. M. Fisher, Jr.,Global Change Biology 4 (8), 809-821 (1998).

Methane emission from rice paddies was modeled as functions of cultivated area, growth duration, grain yield, soil texture, and temperature. The model was validated and calibrated for China. Results on a provincial scale indicated that methane emission is most sensitive to latitude and growing season (early, main, or late). Estimated emissions for the different provinces ranged from 0.15 to 0.86 g/m2 and were in close agreement with observed emissions.

Item #d99mar7

“Carbon Dioxide Fluxes in Moist and Dry Arctic Tundra During the Snow-Free Season: Responses to Increases in Summer Temperature and Winter Snow Accumulation,” M. H. Jones et al.,Arctic and Alpine Research 30 (4) 373-380 (1998).

Summer air temperature was artificially increased about 2°C in moist-tussock and dry-heath tundra in arctic Alaska, and winter snow accumulation was artificially increased, shortening the growing season about four weeks. Ecosystem CO₂ flux was measured weekly to quantify carbon gain or loss during the snow-free season. The elevated temperatures increased the carbon emitted during the snow-free season 26 to 38% in ambient snow and 112 to 326% in artificially deep snow. When winter carbon losses were also factored in, the data indicated that the ecosystems examined are net sources of atmospheric carbon and that global warming would increase carbon losses.

Item #d99mar8

“Litter Decomposition Rates in Canadian Forests,” T. R. Moore et al.,Global Change Biology 5 (1), 75-82 (1999).

The decomposition of plant tissues in 11 litter types from 18 sites across Canada was found to be strongly related to the mean annual temperature and precipitation at the sites, and the ratio of Klason lignin to nitrogen in the original litter was found to be the most important variable in determining litter quality. Climate change is expected to increase current decomposition rates 4 to 7% because of higher temperatures and precipitation. This effect will be slightly offset by the higher lignin-to-nitrogen ratios produced by elevated CO₂ concentrations.