Phytocoenology

(also plant ecology), the study of plant communities, or phytocoenoses. Phytocoenology is a branch of geobotany (the two terms are often used synonymously) and of biogeocoenology. In the late 19th century, the study of the plant cover of numerous countries led to the concept of plant communities—uniform combinations of plants that grow together. This created a need to investigate plant communities as a special subject, and thus a new scientific discipline evolved. At first the discipline was called phytotopography (J. P. Norrlin), then florology (the Polish botanist J. Paczoski, 1891), later phytosociology (Paczoski, 1896; the Soviet botanist P. N. Krylov, 1898), and finally phytocoenology (the German geobotanist H. Gams, 1918; the Soviet botanist L. G. Ramenskii, 1924). The term “phytocoenology” became accepted in the USSR and several European countries, while in other countries the terms “phytosociology” and “plant ecology” are used.

Phytocoenology deals with the floristic, ecobiomorphic, and coenopopulation composition of phytocoenoses, that is, the interrelationships among plants. It also studies the structure, ecology, dynamics, distribution, classification, and history of phytocoenoses. Several trends were evident in the early years of phytocoenology. The geographic approach was introduced by A. von Humboldt, who in the early 19th century established the basic distribution patterns of vegetation by climate. The findings of Humboldt and his followers were synthesized by the German phytogeographer A. Grisebach, who in 1872 published The Vegetation of the World According to Its Climatic Distribution (Russian translation, 1874–77). The works of V. V. Dokuchaev exerted a great influence on the development of Humboldt’s theory.

The Soviet geobotanists G. N. Vysotskii, A. Ia. Gordiagin, and B. A. Keller studied vegetation from the point of view of soil conditions. The Danish botanist E. Warming wrote his Textbook of the Ecological Geography of Plants (Russian translation, 1901–02), which was significant for introducing ecology into the study of vegetation.

In the 19th century, a good deal was written on the structure (layers and mosaics) of phytocoenoses, for example, by the Austrian botanists J. Lorenz (1858) and A. Kerner (1863) and the Finnish botanist R. Hult (1881). Successions were also studied, especially in the USA by F. Clements. In the 20th century, the Third Botanical Congress (1910) recognized the association as an elementary unit of systematics, and various trends in phytocoenology emerged, distinguished by their methods of studying phytocoenoses and of identifying associations. The dominant theory held that the plant cover is composed of discrete, well delineated units. Another theory claimed that the world’s vegetation is continuous and that no sharp boundaries exist between phytocoenoses if growing conditions change gradually.

The theory of the continuity of vegetation and the related concept of the ecological individuality of plant species were substantiated independently by Ramenskii (1910, 1924), the American scientist H. Gleason (1926), the Italian G. Negri (1914), and the French scientist F. Lenoble (1926). At first the theory of the continuity of vegetation failed to receive recognition, but in the 1940’s it was developed successfully by American scientists, including J. Curtis and R. Whittaker; it was later recognized in other countries. Advocates of the theory synthesized the methods of ordination (community arrangement), identifying types of phytocoenoses on the basis of their susceptibility to environmental change, for example, in amount of moisture and level of soil fertility. Ordination has also been used successfully by those who advocate the theory of noncontinuous phytocoenoses, for example, V. N. Sukachev, who arranged the groups of forest associations he had identified into ecological phytocoenological series.

Ecological studies of the earth’s vegetation were synthesized by H. Walter in his monograph Vegetation of the Globe: An Ecological-Physiological Description (Russian translation, 1968–75). A theory formulated in the USSR and later in the USA held that vegetation could be used as an indicator of plant growth conditions; adherents of the theory included B. Keller (1912) and F. Clements (1920). Methods were later developed to devise ecological scales based on vegetation composition, for use as an environmental indicator; significant work in this area was done by Ramenskii (1938; with co-workers, 1956) and H. Ellenberg (1950, 1952, 1974). The Soviet botanist S. V. Viktorov and other scientists also proved that vegetation could be used as an indicator in geological and hydrological research.

The biological trend in phytocoenology, established by the Swiss botanist A. De Candolle (1820, 1832), became highly developed after the publication of Darwin’s On the Origin of Species in 1859. The adherents of De Candolle and Darwin believed that the composition, structure, and dynamics of plant communities are determined not only by climate and soil conditions but also by mutual relations among plants. In the 1870’s and 1880’s this trend was further developed by the Russian scientists N. F. Levakovskii and S. I. Korzhinskii. In the 20th century it was studied by G. F. Morozov and V. N. Sukachev. Sukachev and A. P. Shennikov conducted experiments in the mutual relations among plants in phytocoenoses, thus leading to another field of study, experimental phytocoenology.

A new approach to phytocoenology that evolved in the 1940’s perceives plant communities as components of more complex biologically stagnant systems; this school is based on the concept of biogeoceoenoses (ecosystems) advanced by Sukachev and the British botanist A. Tansley. Comprehensive research has been conducted at observation posts by botanists, zoologists, microbiologists, soil scientists, and climatologists. Their studies have dealt with the amount of organic matter and energy (primary output) produced by phytocoenoses, the role of phytocoenoses in flows of energy and the transformation of matter, the importance of consortia, and the relations of autotrophic plants with one another and with heterotrophic organisms. These investigations reveal the species composition of phytocoenoses (for example, vascular plants, mosses, lichens, algae, fungi, and bacteria, including actinomycetes), as well as the composition of coenopopulations and the structure and dynamics of plant communities, including changes caused by human activity. Such research also indicates which conditions promote maximum productivity from phytocoenoses, including the establishment of artificial high-yield phytocoenoses. Mathematical methods are being used more widely in phytocoenology, especially mathematical models; mathematical statistics has also been introduced.

Soviet botanists have made a major contribution to the development of phytocoenology. They have studied the vegetation of one-sixth of the earth’s surface and have worked out theoretical problems and methods of studying phytocoenoses. Prominent among them are V. N. Sukachev, G. F. Morozov, and A. Kaiander in forest phytocoenology; B. N. Gorodkov, V. B. Sochava, V. N. Andreev, and B. A. Tikhomirov in tundra vegetation; L. G. Ramenskii and A. P. Shennikov in meadow vegetation; and V. V. Alekhin and E. M. Lavrenko in steppe vegetation.

Phytocoenology provides the theoretical foundation for the protection and proper exploitation of natural and planted phytocoenoses and helps increase their productivity. The results of phytocoenological research are used for the beneficial development of natural areas, including forests and meadows, and are employed in geology, hydrogeology, and other disciplines.

Phytocoenological research is conducted in botanical, ecological, geographical, and other specialized scientific institutions in many countries of the world. Phytocoenology is also taught in specialized higher educational institutions.

Articles on phytocoenology are published in botanical, ecological, and general biological journals, for example, the Soviet publications Botanicheskii zhurnal (since 1916), Biulleten’ Moskovskogo obshchestva ispytatelei prirody: Otdel biologicheskii (Bulletin of the Moscow Society of Naturalists: Biological Division, since 1829), Ekologiia (since 1970), Lesovedenie (Forestry, since 1967), and Zhurnal obshchei biologii (since 1940). Major foreign journals include Journal of Ecology (London-Cambridge, since 1913), Ecology (New York, since 1920), Ecological Monographs (since 1931), Vegetatio (The Hague, since 1948), Folia geobotanica et phytotaxonomica (Prague, since 1966), and Phytocoenologica (Berlin, since 1973). The Institute of Biology of the Academy of Sciences of the USSR also publishes works on phytocoenology in the series Geobotanika (since 1932) and Geobotanicheskoe Kartirovanie (edited by V. B. Sochava; since 1963).