Ambient ozone phytotoxic potential over the Czech forests as assessed by AOT40

Ambient ozone (O3) represents one of the most prominent air pollution problems in Europe. We present an analysis on O3 with respect to its phytotoxic potential over Czech forests between 1994 and 2008. The phytotoxic potential is estimated based on the exposure index AOT40 for forests calculated from real-time monitoring data at 24 rural sites. Our results indicate high phytotoxic potential for most of the Czech Republic (CR) with considerable inter-annual and spatial variability. The highest AOT40 values were 38-39 ppm·h. The critical level for forest protection (5 ppm·h) was usually exceeded early in the growing season, generally in May. In years with meteorological conditions conducive to ozone formation, the critical level was exceeded by 5-7 folds as compared to years with non-conducive conditions; nevertheless, all sites consistently exceeded the critical level since 1994. In the extremely hot and dry year 2003, the critical level for forests was exceeded over 31 % of the Czech forested area. More research is needed to translate these exceedances into forest injury in the CR

Nitrogen deposition and its impact on forest ecosystems in the Czech Republic - change in soil chemistry and ground vegetation

A repeated soil survey (1995 and 2006) on 66 ICP Forests pair plots in the Czech Republic revealed a significant relationship between modeled nitrogen deposition and nitrogen concentration in the soil. Nitrogen deposition was modeled for the years 1995, 2004 and 2006. We found a more significant relationship between deposition data in 2004 and soil data in 2006 than between deposition and soil data from the same year 2006. Concentration of total nitrogen in forest soil increased from 1995 to 2006. Forest soil showed effects of increased nitrogen input from the humus layer to around 20 cm depth of mineral soil. The occurrence and cover of nitrophilous species in the herb layer increased from 1995 to 2006 in 25% of the analyzed plots, which corresponds to the nitrogen increase in forest soil. The results suggest that nitrogen deposition still represents a threat for Czech forest ecosystems