Photochemical Air-pollutants—a Threat to Mediterranean Coniferous Forests and Upland Ecosystems

Abstract

Photochemical smog in the densely-populated coastal region of Israel often results in temporary atmospheric ozone concentrations in excess of 0.1 ppm. In view of the rapid growth in urban—industrial development, energy consumption, and motorized traffic, these concentrations are increasing from year to year and the same is presumably true for other Mediterranean countries suffering similar conditions.Moreover, as in California, these photochemical air pollutants can be transported inland under suitable meteorological conditions and may lead to ozone concentrations well above 0.05 ppm even in remote mountain regions with forested slopes. This is the case in the Shaar Hagai canyon leading to Jerusalem, where more than 0.2 ppm oxidant concentrations have been measured and where widespread decline and mortality of Pinus hale-pensis is occuring, accompanied by severe infestation by Matsucoccus josephi scales and Scolytidae beetles. Earlier stages of this decline can also be observed in other planted pine forests in Israel.