CHANGES IN THE CONTENT OF WATER-SOLUBLE SUGARS IN NEEDLES OF SCOTS PINE AND SIBERIAN SPRUCE GROWING IN THE SOUTH OF EASTERN SIBERIA

Abstract

Scots pine (Pinus sylvestris L.) and Siberian spruce (Picea obovata Ledeb.), which are common for the south of Eastern Siberia, differ from each other in their ecophysiological characteristics. Scots pine is more thermophilic and drought-resistant, while Siberian spruce is more hydrophilic and tolerates cooling better. In different seasons, both species accumulate water-soluble sugars (WSS) in their needles, which are one of the factors of cold and drought resistance of needles. The level of WSS accumulation in needles can be influenced by both factors determined by the tree species and territorial ones, associated with the climate of the growing region. For the first time, this study introduces a comparison of changes in WSS content in Scots pine and Siberian spruce growing in the south of Eastern Siberia during two annual cycles. During the observation period, winter 2015-2016 was colder than winter 2016-2017, and the growth period 2015 was warmer and wetter than the same period in 2016. WSS content in Scots pine needles was found to be less subject to fluctuations and, according to the results of most of the observations made, to be higher than in Siberian spruce needles both in more favorable and less favorable conditions for the physiological activity. The exception was the period of November-February 2015-2016 (when WSS content in the needles of both species was the same) and March-April 2016 (when it was higher in Siberian spruce needles). The ability of Scots pine to maintain higher WSS reserve in its needles is possibly one of the mechanisms that allow trees of this species to successfully compete with Siberian spruce and occupy larger territories under the extreme conditions of the south of Eastern Siberia.