Effects of acid rain on mycorrhizal infection and N cycling in forest soils

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6943461

Stroo, H F

Increasing the acidity of simulated rain from pH 5.6 to 3.0 reduced the number of mycorrhizal roots on white pine seedlings by 20% after 16 weeks of exposure. Mycorrhizal infection of red oaks was 25% less at a rain pH of 3.5 than at pH 5.6. Simulated acid rain also caused increases in the N contents, net photosynthesis, and growth of seedlings, as well as decreases in root:shoot ratios and in the concentration of sucrose in the roots. To measure the effects of acid rain on N mineralization, nitrification, and total inorganic N, columns containing samples from the surface horizons of 12 forest soils were exposed to simulated rain at 3 times ambient deposition rates for 16 weeks. The effects on N mineralization varied between soils, with the greatest inhibitions being observed in soils with low organic matter contents. The apparent protection by organic matter was associated with an increase in short-term buffering capacity. The average amount of N mineralized after exposure was not significantly affected by rain pH. Similarly, nitrification was inhibited during exposure to simulated rain at pH 3.5, but was unaffected after exposure. Enrichments from an acid forest soil failed to show the presence of autotrophic nitrifiers, and the effects of temperature and selective inhibitors indicated that fungi were primarily responsible for nitrification in this soil. A fungus capable of heterotrophic nitrification at pH 4.0 was isolated and identified as Absidia cylindrospora Hagem.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 6943461
• Country of Publication: United States
• Language: English

Related Subjects

510200* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACID RAIN
ATMOSPHERIC PRECIPITATIONS
CARBOHYDRATES
CHEMICAL REACTIONS
CONIFERS
DENITRIFICATION
DISACCHARIDES
DISEASES
FORESTS
FUNGAL DISEASES
INFECTIOUS DISEASES
MYCORRHIZAS
NITRIFICATION
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
PH VALUE
PINES
PLANTS
RAIN
ROOTS
SACCHARIDES
SACCHAROSE
SEEDLINGS
SOILS
TREES