Effect of acid rain on soil microbial process
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Effects of soil acidity on microbial decomposition of organic matter and transformation of N in an acid forest soil were investigated. In the oak-leaf-amended pH-adjusted acid soils, CO2production in 14-and 150-day preincubated samples decreased by about 6 and 37%, respectively. In the control (unamended) acidified soils, reductions in CO2 production of 14% in 14-day preincubated samples and of 52% in 150-day samples were observed.
Ammonia formation in the pH-adjusted acid soil was about 50% less than in the naturally acid soil. Increased rates of ammonification and nitrification were observed in the pH-adjusted neutral soil. Little autotrophic and heterotrophic nitrifying activity was detected in naturally acid and acidified forest soils.
The rate of denitrification was rather slow in acid soils, and at greater acidities N2O was the predominant end product.
The abundance of N-fixing free-living bacteria was very low in acidic and acidified forest soils, and N gains by asymbiotic bacterial fixation in an acid forest ecosystem may be insignificant. These results suggest that further acidification of acid forest soils by addition of H2SO4 or by acid precipitation may lead to significant reductions in the leaf litter decomposition, ammonification, nitrification, and denitrification and thus reduce nutrient recycling in the forest ecosystem.
Ammonia formation in the pH-adjusted acid soil was about 50% less than in the naturally acid soil. Increased rates of ammonification and nitrification were observed in the pH-adjusted neutral soil. Little autotrophic and heterotrophic nitrifying activity was detected in naturally acid and acidified forest soils.
The rate of denitrification was rather slow in acid soils, and at greater acidities N2O was the predominant end product.
The abundance of N-fixing free-living bacteria was very low in acidic and acidified forest soils, and N gains by asymbiotic bacterial fixation in an acid forest ecosystem may be insignificant. These results suggest that further acidification of acid forest soils by addition of H2SO4 or by acid precipitation may lead to significant reductions in the leaf litter decomposition, ammonification, nitrification, and denitrification and thus reduce nutrient recycling in the forest ecosystem.
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