Forest Biota under Changing Concentration in Acidifying Compounds in the Air and Their Deposition

Effects of acid deposition on forest ecosystems despite a drastic decrease in sulphur emission and deposition at the end of the 1990s are still among the most significant ecological issues. The key reason for this is that atmospheric concentrations of ammonium and nitrate which have a tendency to increase in the last period became the main acidifying compounds of precipitation. These changes in acid deposition resulted in main objectives of the presented study which were to estimate the effect of rain acidity and atmospheric deposition of pollutants on crown defoliation and diversity of soil microarthropods, stream macrobenthos and small mammals (rodents) on territories under changing regional pollution level. Investigation was carried out in 3 Lithuanian Integrated Monitoring Stations over the period 1994-2004. The obtained data indicated that lower life forms were more affected than higher. Acid deposition was shown to have the most significant effect on pine tree defoliation as well as on the diversity of soil microarthropods and diversity of stream macroinvertebrates and least on the diversity of small mammals. These results have indicated that regional pollution level which is below critical level for forest ecosystem has a significant effect on the biota.