DETERMINATION OF PHENOLOGICAL PERIODS OF TREES BY THE METHOD OF CONDUCTOMETRY

The electrical conductivity of the near-cambium layer of four tree species in the Southern Baikal region was measured for two years: Pinus sibirica Du Tour., Abies sibirica Ledeb., Betula pendula and Picea obovata var. coerulea Malysh. The electrical conductivity of all the selected species has been established to vary from almost zero level to values above 20 μS depending on the season. This conductivity variation interval has two distinct ranges: 1) 0 - 13 μS; 2) 14 - 22 μS. The first range is typical for trees that are in the stage of induced or deep dormancy, the second – for a period of a high physiological activity. Changes from one to the other range are associated with the onset of different natural seasons and usually occur quite rapidly. During the periods of the winter rapid thaw (the period of the induced dormancy), the level of electrical conductivity, which we conventionally accepted as a criterion characteristic of the spring-summer vegetation, does not significantly exceed 20 μS in all trees, but it can enter the “start” boundary of the spring phase change in fir and cedar.