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the study of seasonal phenomena in nature, including the time and causes of their occurrence. The term “phenology” was proposed by the Belgian botanist C. Morren in 1853. Phenologists study the seasonal phenomena of the plant and animal kingdoms (biophenology) and record the dates of climatic changes, for example, the appearance and disappearance of the snow cover, the first and last frosts, and the freezing over of bodies of water and the breaking up of the ice.
In phytophenology, the phenological study of plant life, the seasonal phases of development are recorded, including the swelling and opening of buds, leaf growth, the beginning and end of blossoming, the ripening of fruit and seeds, autumn coloration of leaves, and leaf fall. In zoophenology, which deals with animal life, important phenomena observed among mammals include the end of hibernation, beginning of mating, appearance of young, and seasonal shedding and migrations. Among birds, the basic phenomena observed are nesting, laying and hatching of eggs, the first flight of fledglings, and the spring and fall flights of migratory species. The main stages observed in the life of arthropods include the end of winter dormancy, hatching of larvae, appearance of adult insects from cocoons, egg laying, development of larvae and cocoons, appearance of new generations, and diapauses.
Biophenological research is conducted on individual organisms, populations, biological communities of domestic and wild animals, and the biosphere as a whole. Geographical research in phenology deals with seasonal changes in entire natural complexes, including their biological and nonbiological components. Research is conducted within individual natural boundaries, landscapes, provinces, countries, and natural regions. Annual cycles in geographical complexes and biological communities are subdivided into natural (phenological) seasons and subseasons.
Historical sketch. Observations of seasonal phenomena were made in ancient times during the period of gathering, hunting, and primitive agriculture. Modern scientific phenology first developed in the 18th century. Peter I the Great, concerned about the choice of sites for parks in the environs of St. Petersburg, wrote to A. D. Menshikov in 1721: “When the trees begin to open, order leaves of them sent to us each week, glued on paper, with an inscription telling the date, so that we can learn where spring begins earliest” (cited in I. N. Beideman, Metodika feno-logicheskikh nabliudenii pri geobotanicheskikh issledovaniiakh, 1954, p. 6). In 1734 the French scientist R. de Reaumur began studying the relationship between temperature and the seasonal development of grains and insects. C. Linnaeus began a series of phenological observations at the Uppsala Botanical Garden in 1748 and organized the first network of observation posts in 1750. By the mid-19th century, phenological observations were being made throughout the major countries of Western Europe and in Russia. A. I. Voeikov and D. N. Kaigorodov played an important part in the development of phenology in Russia. In the 20th century the field was studied in all the countries of Central Europe and in the USA and in other countries, including India.
Methods and tasks. The traditional methods of phenology are visual observation and the recording of seasonal phenomena. The publication of works on observation procedure (including methodological instructions) and of atlases indicating plant phases and seasonal phenomena in the animal kingdom facilitate the comparison of observations conducted by different persons.
The observations made at phenological posts are compiled and studied to establish geographical patterns, which are depicted on phenological maps. The average long-term progression of seasonal phenomena by latitude, longitude, and elevation (mountains) varies in different geographical regions, at different seasons, and for different groups of phenomena. In the central regions of the European USSR, the stages of spring and summer plant development progress from south to north at an average rate of about 40–50 km a day, and birds migrate at a rate of about 50–60 km a day. The rates of the longitudinal movement of seasonal phenomena are determined primarily by a given region’s proximity to the Atlantic Ocean. For example, spring begins earlier in western regions than in more continental regions at the same latitude. However, the transition from winter to summer in the continental interior occurs more rapidly than along the ocean, and, despite the late spring, grain planted in the Volga River valley ripens earlier than grain planted in France. In the mountains, spring and autumn phenomena are delayed an average of three days for each rise in elevation of 100 m. In some years, seasonal phenomena deviate significantly from long-term averages, making the management of agriculture and other seasonal economic sectors more difficult.
Ecological phenology is the study of the endogenic and exogenic factors that determine the onset of seasonal phenomena. Endogenic factors are hereditary. For example, snowdrops bloom in early spring, while asters and chrysanthemums bloom in late summer, and rooks arrive in early spring, while cornrakes do not arrive until early summer. Exogenic factors are determined by the environment. One or two factors are crucial in each geographical region, for example, humidity in the tropics, the thermal regime in the temperate zones, and the radiation and thermal regimes in the arctic. Different groups of seasonal phenomena depend on environmental factors to varying extents. The resumption of growth in spring is determined primarily by thermal conditions, while the fall of the leaves in autumn depends on radiation (the number of hours of daylight) as much as it does on the thermal regime. Phenological spectra provide one method of presenting phenological observations of plant life. The occurrence of seasonal phenomena among animals is often related to feeding conditions. For example, insectivorous birds arrive when a sufficient number of insects appear in the spring. Specialists in ecological phenology formulate models that help clarify the relationship between the onset of seasonal phenomena and the total of endogenic and exogenic factors. This work is essential for phenological forecasting.
Organization of observations. In addition to its importance in biological and geographical research, phenology is valuable in improving the efficiency of applied scientific services.
Most countries have established networks of phenological observation posts to identify geographical phenological patterns. The USSR began operating such a network in 1924 under the auspices of various regional-studies organizations; in 1939 the network was put under the authority of the Geographical Society of the USSR. Between 1965 and 1975, approximately 3,500 volunteer corresponding members had joined the society. The observation posts are supervised by the society’s phenological division, with the help of local organizations in Moscow, Vilnius, Riga, Krasnoiarsk, Irkutsk, and other cities. The results of long-term phenological observations at a specific location are published in calendars of nature in the form of a table or graph with average times of local phenomena observed over the course of years. The calendar of nature is a valuable reference source for studying the occurrence of many seasonal phenomena. Phenological research is conducted by botanical, zoological, and geographical institutions, including institutes of the Academy of Sciences of the USSR. Geographical institutions conduct comprehensive research on the structure of geographical complexes and ecosystems. State preserves also conduct comprehensive research by compiling chronicles of nature.
Economic importance. Phenological patterns are of great importance in compiling regional calendars for several sectors of the economy, such as agriculture, the timber industry, and hunting. These calendars are used to develop measures for the protection of nature and to control pests and diseases of plants, as well as parasites and transmissible diseases of humans and livestock. They are also used in apiculture and sericulture. Phenology also informs the aviation industry of massive bird migrations and indicates the best seasons for telemetering the earth’s surface by helicopter, airp.ane, and rocket.
Phenological research is used in selecting sites for sanatoriums and houses of rest, as well as tourist routes and excursions. Phenological maps, especially large-scale maps, are essential for planning seasonal production. Phenological observations help identify local natural indicators that can be used to determine seasonal phenomena and predict the character of the current growing season. They are especially important when introducing new plant and animal species and developing new territories.
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Ibid., book 2. Moscow, 1949.
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