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.

222 A phenological atlas of plants temperature drop (Elagin, 1976). The indicator of autumn air temperature decline in this case is the date since which steady cooling of mean and minimal daily temperatures is observed. 14. BEGINNING OF LEAF FALL, SENESCENCE IN HERBACEOUS PLANTS International phase code BBCH 93 (Growing stage.., 2001; Meier et al., 2009) Phase description The beginning of leaf fall is recorded on the day when the first au tumn-color leaves (needles) have fallen from 10% of plant specimens along the route. The first fallen leaves in birch, aspen, w illow are easy to see on the ground; the process in pine and spruce can be visualized by slightly shaking branches. The first specimens of senescing herbaceous plants appear in this period. Plants of some species die in the middle of the summer. In her baceous plants this phase is recorded on the day when 10% of specimens are dead to the ground. Leaf fall progress is promoted the most by heavy frost spells (down to -3 - -5°C) and wind, the process after these events being very intensive. Further info Elagin I. N. and Lobanov A.I. (1979): Autumn leaf fa ll usually begins simultaneously with leaf coloration, and in plants of genera Alnus, Populus it is since the fall of the first green leaves. Fenolog .rgo.ru : The pace of leaf fall varies among plants: quite gradual in some (birch), while rapid in others (aspen, willows). The day when the first autumn-colored leaves fall is considered the beginning of leaf fall. In the species that may not always have explicit autumn leaf col oration the beginning of leaf fall is identified by the first fallen leaves appearing on the ground under a tree or shrub (to be distinguished from summer leaf fall caused by drought or heat). Leaf fall begins soon after the beginning of leaf coloration and is at first rather inconspicu ous. If, however, warm autumn weather is all of a sudden replaced by