Quantification of ozone uptake in a Pinus canariensis stand in Tenerife, Canary Islands by means of sap flow measurements

Wien

2006

Unselbständiges Werk

200134496

Ozone uptake was studied in a pine forest in Tenerife, Canary Islands, an ecotone with strong seasonal changes in climate. Ambient ozone concentration showed a pronounced seasonal course with high concentrations during the dry and warm period and low concentrations during the wet and cold season. Ozone uptake by contrast showed no clear seasonal trend. This is because canopy conductance significantly decreased with soil water availability and vapour pressure deficit. Mean daily ozone uptake averaged 1.9 nmol m-2 s-1 during the wet and cold season, and 1.5 nmol m-2 s-1 during the warm and dry period. The corresponding daily mean ambient ozone concentrations were 42 and 51 nl 1-1, repectively. Thus we conclude that in Mediterranean type forest ecosystems the flux based approach in more capable for risk assessment than an external, concentration based approach. In 1990 and 1991 data from about 20 sites were available. Since 1992 data from about 40 sites were used.