Stomatal ozone flux and visible leaf injury in native juvenile trees of Fagus sylvatica L.: a field study from the Jizerske hory Mts., the Czech Republic
Abstrakt
The study was carried out at six sites in the Jizerskehory Mts. in the north of the Czech Republic. At all these sites, ranging in altitude between 460 and 962 m a. s. l., and during the period from June to September in 2008, O-3 concentrations and environmental parameters important for accumulated stomatal O-3 flux (AF(st)) into Fagus sylvatica leaves were measured.
At five sites, visible injury on Fagus sylvatica L. juvenile tree leaves was observed. A combination of actual O-3 levels in the Jizerkehory Mts. and environmental conditions, though relative air humidity and air temperature significantly limited stomatal conductance, has been sufficient enough to cause O-3 uptake exceeding the critical level (CL) for forest ecosystems.
The AFst values ranged between 13.4 and 22.3 mmol O-3 m(-2). The CL for the accumulated stomatal flux of O-3 above a flux threshold 1.6 nmol m(-2) s(-1) (AF(st)1.6) was exceeded at all sites from ca 45 to 270 % (160 % on average).
The CL of 5 ppm h(-1) for AOT40 (accumulated O-3 exposure above threshold of 40 ppb) was exceeded at four sites. The relationship between visible injury on O-3 indices was found.
The conclusions based on AOT40 and AF(St) are not the same. AF(St) has been determined as better predictor of visible injury than AOT40.