After taking a close new look into soil chemistry and where calcium comes from, scientists said Wednesday that acid rain may be doing less damage to forests than anticipated.

In a report published in Nature, researchers from six institutions said that some trees, especially spruce and firs, cooperate with soil fungi to dissolve calcium directly from a mineral called apatite.

The important point is that this alternate source of calcium may account for what has been seen as excess calcium that scientists see leaving the forests via streams. In the past, the extra calcium flow was blamed on acid rain, corrosive enough to leach out the mineral nutrient.