Quantifying ozone uptake and its effects on the stand level of common beech (Fagus sylvatica L.) in Southern Germany

Stand level O3 fluxes were calculated using water balance calculations for 21 Common beech (Fagus sylvatica L.) stands and O3 data from 20 monitoring stations in Southern Germany. For this intention, the daily loss of water by evapotranspiration per stand area was set against the daily O3 uptake. During the last 30 years, O3 uptake ranges between 0 and 187 mmol ha−1 d−1 per stand area. Cumulative O3 uptake (CUO3), ranging between 0.1 and 0.7 mmol m−2 yr−1 per stand area, shows increasing trends since 1971 with considerably greater values at high altitudes. Effects in radial growth were used to derive an initial approximate critical threshold value for O3 impacts on the vitality and growth of mature beech stands in Southern Germany. It is concluded that this concept of O3 flux estimation in combination with dendroecological analyses offers both a site specific and regional applicable approach to derive new critical levels for O3.