Макарова, О. А. Фенологический атлас растений / Н. В. Поликарпова, О. А. Макарова ; М-во природ. ресурсов и экологии Рос. Федерации, Федер. гос. бюджет. учреждение «Гос. природ. заповедник «Пасвик» ; [худож.: Хохлов В. А. ; пер.: Кислова О. С.]. - Рязань : Голос губернии, 2016.

Descriptions of principal plant phenophases 219 with autumn-colored leaves visible from afar, so called “yellow flags". Autumn phases in pine and spruce are less conspicuous, since only part of the foliage gets discolored: on 2-3-year-old branches in pine, on 5 -7 -year-old branches in spruce. Needle coloration in pine in the High North begins in the second half of August on lower parts of branches. In spruce this phase begins later, most often in late September or early October, and is less pronounced than in pine. The weather is an important factor influencing the course of leaf col oration and leaf fall. On a warm and dry autumn foliage would begin to change color earlier; the hues would be brighter (“golden autumn"). On a wet and sunless autumn leaf coloration would be delayed and less colorful. If however air temperature rises significantly in mid to second half of September, many trees and shrubs would still change foliage color quickly and sometimes fully. In some cases, leaf coloration, especially in birch, may be due to dis ease (pathogenic fungi - rust), and may begin earlier than usual. Such yellowing of the leaves should not be confused with the natural coloring to avoid recording a distorted course of events and complicating the statistical analysis of long-term data. Large-scope rust damage may sometimes recur, affecting vast areas again after a 2-3 year pause. The foliage would be colored dirty brownish yellow. Leaf fall would begin earlier in this case, but the trees still have enough time to pass through the phase of ‘true’ autumn yellowing. Thus, fungal damage of leaves and needles should also be recorded as such, but is not to be confused with natural leaf coloration and leaf fall. Further info Fenolog. rgo.ru- . End of vegetative development. The monitoring of leaf coloring and leaf fall in autumn is to cover the entire tree crown. Autumn events are comparatively slow and not concurrent even within the same species. This is very often observed in birch, aspen, willow. Aspen trees with foliage colored in red in autumn particularly stand out. Their leaves change color and fall quicker than in trees with yellowing leaves. The timing of autumn phenological events in woody species is controlled not only by the weather, wintering environment or the plants’ development