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.

A phenological atlas of plants More than 50% flowering of Heather microclimatic conditions in such sites modify the rates of phase transition as compared to other plants of the same species. On the other hand, such plants can be specially studied for the effect of microclimate on the development of trees and shrubs. Where a tree or shrub species is represented by just a few specimens (two or three), the date of phase onset is the day when traits of the phenophase are found in one specimen, and the phase peak is when the traits are found in a half of specimens. The number of specimens sampled should be specified in the records. Phenological observations on woody plants should be commenced on the day when daytime air temperature in the shade is near or slightly above 5°C. The onset of sap flow in downy birch may be timed to this day. To capture this event, the trunks of several trees are pierced on the south-facing side at around 1.5 m above the ground with a thick needle or awl to reach slightly into wood. The onset of sap flow is recognized by sap droplets emerging from the holes. Given the relevant temperatures, sap flow in birch in the Murmansk Region begins in April. By that time the soil had usually fully thawed. The rest of development phases in woody plants are determined by the following indicators: