Sunday, November 13

UCR News: Acid rain threatens forests in more ways than previously thought

UCR News: Acid rain threatens forests in more ways than previously thought: "Acid rain threatens forests in more ways than previously thought
(July 8, 2002)

RIVERSIDE, Calif. -- UC Riverside Earth Scientist Martin Kennedy and colleagues report in the Proceedings of the National Academy of Sciences that acid rain, by leaching essential metal nutrients (such as potassium, calcium, and magnesium) from topsoil, may pose a far graver threat to forests than has been previously estimated. This result would especially interest ecologists, biologists, geologists, and policy makers.

'Our work shows that in unperturbed natural ecosystems a very small pool of these nutrients is available and this comes from the atmosphere, mostly as dilute amounts dissolved in rain that then get deposited in topsoil,' said Kennedy. 'The tight budget of these nutrients is a concern because if the budget is perturbed, the forests are at risk.'

If deprived of a certain critical nutrient, such as calcium, a tree faces the risk of dying. In parts of Germany, for example, trees are already dying not from the direct effects of the acid, but from magnesium deficiency, this magnesium loss from the soil stemming from leaching by acid rain. Such leaching results in the loss of topsoil nutrients to groundwater and eventually to rivers.

Kennedy noted that plant roots cannot access all nutrient elements in the soil; some elements are bound in minerals and rocks. 'In our study, we were attempting to determine what fraction of the total elements available in the soil the plants could access. We found it was a very small proportion.'"

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