Abstract: Two-year-old seedlings of Pinus massoniana were planted in acidified soils to explore the effects of acid rain and ectomycorrhizal fungi (EMF) on soil organic carbon content, soil aggregate composition and soil nutrient (N, P, K) contents. We set up three levels of simulated acid rain \[pH 5.6 (CK), pH 4.5, and pH 3.5\] and applied two ectomycorrhizal treatments (inoculated, noninoculated) in each level of acid rain. The pH 3.5 treatment significantly reduced the contents of available P, total P, available K, ammonium N, nitrate N and total N in soil, while inoculation with EMF effectively alleviated such negative effects of pH 3.5 treatment. Acidification treatment increased the content of microaggregates (<0.053 mm, 0.053-0.25 mm) and reduced the content of macroaggregate (0.25-2 mm). Compared with control (pH 5.6), the pH 3.5 treatment significantly deceased the contents of organic carbon fractions, especially those with 0.25-2 mm size aggregate. Inoculation with EMF significantly increased the content of organic carbon. Acidification treatment significantly decreased the contents of soil light-fraction organic carbon (LFOC) and heavy-fraction organic carbon (HFOC), whereas inoculation with EMF significantly increased the contents of LFOC and HFOC. Our results indicated that inoculation with EMF could alleviate the negative effects of acid rain stress on soil quality.

Key words: canopy phenology, digital camera, near-surface remote sensing, radiometer, spectrometer, vegetation index.