Der Austausch von Carbonylsulfid (COS) zwischen Vegetation und Atmosphäre unter erhöhter CO 2-Umgebungskonzentration

The responses of photosynthetic plant gas exchange, COS uptake and carbonic anhydrase (CA) activity were studied on Quercus ilex (Holm oak), and beech Fagus sylvatica L

grown under ambient (350 ppm) and elevated (800 ppm) CO2 levels for three years. Both growing CO2 conditions resulted in a linear relationship between the consumption of COS and the ambient COS concentration. Under COS free conditions no release of COS was detected. The dependence over the entire measurement range with a linear regression was not possible; therefore a no linear approximation on basis of the parameters Deposition velocity (vD) and compensation point was developed. Under elevated CO2-levels the response of the vegetation is not uniformly, since the parameters (vD) and compensation point (KP) are highly scattered under elevated CO2 concentration. COS uptake and the activity of the enzyme carbonic anhydrase (CA)

which is the enzyme for the COS uptake, was significantly reduced in Quercus ilex L measurements while there was no significant trend in Fagus sylvatica L measurements. Both species react differently under elevated CO2-concentration at constant conditions. This work identifies relevant errors in the existing model for the determination of the global sink strength for COS of the vegetation. These errors are in the range of 200 % [195 %... 500 %] According to the results of this investigation a new model for the estimation of the global vegetation sink for COS was developed. Based on this result the global COS uptake of the vegetation was estimated to be 0,909 -2,750 Tg/a. Under elevated CO2 concentration the global COS sink strength of the vegetation is about 0,687-2,561 Tg/a. Finally this model is modified and abstracted this way, which it can be applied to model the gas exchanges between vegetation and atmosphere that are correlated to each other and which have influence on the composition of the chemistry of the atmosphere. So generally the model can be used to represent the participation of the vegetation on climatic processes.