Ecophysiological study of the growth of conifers in Korea in acidified soil with elevated CO2: The role of ectomycorrhizal infection

Several Pinaceae species (Pinus and Larix sp.) in northeastern Asia, especially Korea, show symptoms of decline due to soil acidification and air pollution. In the industrial area of northwest Korean, growth and physiological activities of Pinus koraiensis and P. rigida are adversely influenced by increased deposition of fluorine (F), chlorine (CI) and Manganese (Mn), involving both wet and dry deposition; these also have harmful effects on the ectomycorrhizal status. The ectomycorrhizal infection level at the damaged site was 30% less than at a control site. To determine the role of ectomycorrhizal symbiotic association with seedlings of P. densiflora, P. koraiensis, P. rigida and Larix kaempferi during progressive soil acidification, the relation between relative total dry mass (TDM) and the molar ratio of base cation to aluminum (BC/Al) was examined. The TDM of P. koraiensis and L. kaempferi seedlings was approximately 40% at a BC/Al ratio of 1.0, but that of P. rigida and P. densiflora was approximately 50% at the same BC/Al ratio. With increasing amount of Hsup(+) added to the soil, the water-soluble concentrations of Ca, Mg, K, Al and Mn increased, especially below a soil pH of 3.8. Development of ectomycorrhizae, i.e. Pisolithus tinctorius (Pt), Ectodrench (EC) or Cenococcum geophilum (Cg) in all four test species was significantly greater in the 10 and 30 mmolHsup(+)/kg treatments than in control treatments. Ectomycorrhizal development in the 60 and 90 mmolHsup(+)/kg treatments was significantly lower than the other treatments. Atmospheric CO2 increases yearly that may affect mycorrhizal growth and diversity in forest ecosystems through host plant physiology. The ectomycorrhizal development of each species was significantly higher under elevated CO2 concentration (720micromol/mol) than at ambient levels (360micromol/mol) in the present study. The P concentration in needles and roots following inoculation with Pt, EC or Cg was significantly higher in all species than without inoculation, at both CO2 concentrations. Furthermore, no photosynthetic down-regulation was found in any species when inoculated with Pt, EC or Cg, and photosynthesis was significantly higher than in non-inoculated seedlings at both CO2 concentrations. Stomatal limitation in each species at each CO2 concentration was less than in non-inoculated seedlings.