The question of the effect of warming of the cli-mate on trees has been raised before and the in-fluence of global warming on trees at mid- to high latitudes is becoming clearer now. Rapid climate changes can greatly influence tree metabolism and development, and climate-related traits of tree spe-cies, such as timing of growth and reproduction should be studied in that regard. The aim of this work was to study the effect of temperature on the activity of the photosynthetic apparatus of conifers during the autumn photoperiodic response and win-ter dormancy. As objects of the study we used one- year needles of Siberian fir (Abies sibirica Ledeb.), Scots pine (Pinus sylvestris L.), Siberian pine (Pinus sibirica Du Tour.) and Siberian spruce (Picea obovata Ledeb.). Chlorophyll fluorescence parameters were recorded on a fluorimeter JUN-IOR-PAM. The data show a significant influence of temperature on the regulation of the activity of the photosynthetic apparatus of conifers not only in the period of forced rest, but also in preparation for the transition to a phase of deep rest. Also we found out the differences significance of the temperature factor in the regulation of winter dormancy phase between the species. We conclude that all of the tree species studied were characterized by different depths of dormancy. Dark-needle species, espe-cially fir were characterized by a smaller depth of dormancy and a shorter duration of dormancy. Per-haps in the conditions of climatic warming the Abies sibirica trees emerge from the forced dormancy even during the brief winter thaws, which previously have not been typical for the studied area. Water losses that arise due to the resumption of photo-synthetic activity and gas exchange cannot be compensated in winter conditions due to frozen soils, which can result in desiccation and death of the needles.