February 28, 2007
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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 4, APRIL 1999
Transferring Soils from High- to Low-Elevation Forests Increases
Nitrogen Cycling Rates: Climate Change Implications, S. C. Hart and
D. A. Perry,Global Change Biology 5 (1), 23-32 (1999).
Intact soil cores were transferred from a high-elevation, old-growth
forest to a forest 800 m lower with a mean annual air temperature 2.4°
C higher and a mean annual soil temperature 3.9° C higher. Soil
nitrogen mineralization and nitrification more than doubled, and
inorganic-nitrogen leaching also increased.
Changing Sources of Nutrients During Four Million Years of Ecosystem
Development, O. A. Chadwick et al.,Nature 397,
In humid environments, rock-derived nutrients are leached out of the
soils, leading to nutrient depletion. However, the productivity of
rainforests in Hawaii has remained constant because of nutrient inputs
from the atmosphere. Needed cations are supplied by marine aerosols, and
phosphorus is supplied by airborne dust that is blown to Hawaii from more
than 6000 km away in central Asia.
Three Decades of Observed Soil Acidification in the Calhoun
Experimental Forest: Has Acid Rain Made a Difference? Daniel
Markewitz et al.,Soil Sci. Soc. Am. J. 62 (5), 1428-1439
For the past 30 years, the hydrogen-ion budget for the Calhoun
Experimental Forest in South Carolina was studied, and the accumulated
nutrients, tree-root respiration, and organic acids produced from the
breakdown of litter were measured. Acid rain was found to accelerate the
acidification of forest soils, stripping the soil of nutrients and
minerals and hampering the soils ability to buffer trees from toxic
substances. Soil acidification was found to increase by 38% at the Calhoun
Forest during the observation period. Soil pH decreased by as much as one
unit in the top 14 in. of soil and by half a unit in the next 14 in. A
decrease in soil sulfate levels over the past decade was also found and
was attributed to stricter air-quality standards.
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