Seasonal changes of pH and buffer capacity of aqueous homogenates of Vaccinium vitis-idaea and Vaccinium myrtillus leaves

The newly formed leaves of both Vaccinium species show in June and July the lowest pH values, 3.4-3.7, which gradually increase up to 4.6 in November. The bi- and triennial leaves of Vaccinium vitis-idaea are less acid and show much morę limited seasonal decrease of acidity. The buffer capacity against acid of the current year leaves ,of the two species shows in summer a high level of values (a constant one for Vaccinium myrtillus), It decreases in autumn to achieve that of bi- and triennial leaves of Vaccinium vitis-idaea. The buffer capacity values are influenced to a limited extent by the increase in air-pollution, much smaller than that noticed for Pinus silvestris co-existing with Vaccinium in the same ecosystems