( s in a test plot to replicate soil cond...)Acid rain causing decline in sugar maples, say researchers

Nitric and sulphuric acid in acid rain leaches calcium from the soil. Calcium is the second most abundant plant nutrient (after nitrogen). In addition, the loss of calcium leads directly to more acidic soils. When soils become too acidic, such trees as sugar maples become stressed and have a harder time growing or producing seeds and seedlings.

"Because of the detailed measurements for the last 50 years, we know almost exactly how much calcium was removed by acid rain," said Fahey. "Our treatment was designed to replace just that amount of calcium to bring the system to what it was like prior to the acid rain era."

The study used two 10-hectare (25-acre) watersheds. On one 25-acre site, a calcium-rich mineral called wollastonite was spread in pellet form by helicopter in October 1999. The other site served as a control.

While the pellets dissolve slowly over five to 10 years, the researchers were surprised to find that by summer 2002, the soil acidity in both the top and lower layers of the test plot neutralized from being highly acidic to more acceptable levels for sugar maples. The researchers also found that by the second year, calcium levels in the maples' leaves had risen.

Acid rain also increases levels of the trace nutrient manganese in the soil, which can be toxic to trees in higher doses. By year four and five, manganese in the leaves had declined to healthier levels. In addition, seed production and the density and size of sugar maple seedlings all increased in the few years following treatment, compared with the untreated neighboring plot.

The researchers also found that the communities of mycorrhizae -- soil fungi that help provide more nutrients to plant roots -- were substantially greater around the roots of both seedlings and mature sugar maples in the treated plot. Future research wi
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Source:Cornell University News Service