这些松针给土壤增加了很多酸性。

Those needles add a lot of acid to the soil.

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酸雨现象不但导致湖泊酸性提高，使许多鱼类繁殖能力下降；而且随着土壤里酸性物质的增加，树木的生长速度开始放慢，对疾病的抵抗力下降。

The result is increased acidity in lakes, which has curtailed the ability of many fish to reproduce, and in the soil, which has slowed the growth of trees and increased their vulnerability to disease.

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