New Study Casts Doubt on CO_2 Uptake by Trees

摘要

A recent study by researchers at two national laboratories and two universities concludes that the potential for forest soils to soak up atmospheric carbon is highly dependent on the lifespan of the forest's tree roots. As a result, some species of trees likely will do a better job than others in absorbing carbon dioxide, the key greenhouse gas, and transferring it through roots to soil. The study, published in the November 21, 2003 edition of Science magazine, said large differences in root replacement rates among two observed tree species suggests that current predictions of how carbon absorption by soil will act to ameliorate global warming may have to be reconsidered. The study was performed by researcher's at the Energy Department's Argonne andOak Ridge national laboratories, Duke University and the University of Illinois at Chicago and primarily funded by the Department of Energy's Office of Science. The study used a new technique to measure the longevity of roots-the source of some of the carbon that would be transferred by decay into the soil-in trees growing in forest plots infused with a computer-controlled flow of carbon dioxide (CO_2). The flow was metered to maintain the higher atmospheric CO_2 levels predicted by many scientists tooccur in the middle of the century Such an increase in CO_2, primarily caused by the combustion of fossil fuels and clearing of the world's forests, underlies the global warming that these scientists say has already begun.