(b. Coire, Switzerland, 3 August 1884; d. Montpellier, France, 20 September 1980),
plant sociology, ecology, botany.
Braun-Blanquet founded the Zürich-Montpellier school of plant sociology (or phytosociology). The school was so named because Braun-Blanquet studied at Zürich University in Switzerland, but carried out most of his research in the French city of Montpellier. The school spread rapidly in south and central Europe and became the dominant European approach to phytosociology (alongside the Physionomic-Ecological, Uppsala, and Russian Schools). It identified adaptations to environmental factors not brought to light by traditional methods, thus playing an important part in the history of ecology. In 1930 Braun-Blanquet established the “Station Internationale de Géobotanique Méditerranéenne et Alpine” (SIGMA, International station for Mediterranean and Alpine geobotany). This school of phytosociology also became known by the neologism sigmatism. In 1974 Braun-Blanquet was awarded the Gold Medal of the Linnean Society of London.
Background and Education. Born Josias Braun in Switzerland in Coire (Chur in Alemannic dialect), the regional capital of the Grisons canton, the scientist came from a humble background: His father, Jakob, was a state employee and his mother, Elizabeth Kindschi, was a housewife. After business studies he began his own study of botany in the Swiss Alps before studying the subject at Zurich University, where he was taught by the renowned Helvetian botanists Eduard Rübel (1876–1960) and Carl Schroeter (1855–1939). In Geneva, where he stayed in 1907 and 1908, he was taught by Casimir de Candolle (1836–1918), son of Alphonse de Candolle (1806–1893) and grandson of Augustin-Pyramus de Candolle (1778–1841), and by John Briquet (1870–1931), then director of the Geneva Botanical Conservatory and Gardens. Briquet was also behind the adoption of the botanical nomenclature international rules. This interest in systematics was consistent with Braun-Blanquet’s subsequent studies on plant community taxonomy. It had long been of interest to ecologists. The general appearance of a plant community is the outcome of the particular look of each plant. It is therefore related to the growth-forms of plants that compose vegetation. Now, as growth-forms represent the state of the adapted plants, any physionomical classification of plant communities takes on an ecological significance more or less evident, according to the advancement of biological forms studies.
Birth of Plant Community Study. In 1805, in his Essai sur la géographie des plantes, Alexander von Humboldt (1769–1859) had described Calluna heath vegetation in the following way: “Heathers, this association of Erica vulgaris,Erica tetralix, Icmadophila and Hoematomma lichens, spread between the most northern extremity of Jutland up to 52° N, through Holstein and Luneberg” (p. 17). This reasoning amounted to defining a plant community by its main floristic components. Humboldt also geographically localized the extension of this “association” (in contemporary terms, “plant formation”) in relation to climate. In 1822, the Danish botanist Joakim Frederik Schouw (1789–1852) proposed a method for defining associations: He recommended adding the suffix -etum to the root of the dominant plant’s name. Thus, Fagetum denoted an association of which the dominant species is the beech (Fagus sylvatica), and Quercetum an association where the oak (Quercus) is dominant. According to this method, the dominant species provides the name of the association, but this does not imply an exhaustive floristic survey of the community.
In 1863, the Austrian botanist Anton Kerner von Marilaün (1831–1898) reversed the traditional relationship between plant communities and environment. Instead of starting from environmental factors in order to define communities, he described communities according to their own characteristics of physionomy and floristic composition. This reasoning provided a foundation for modern plant sociology, as it made possible discovery of adaptations to environmental factors previously obscured by communities classed according to environmental criteria. Until then, plant communities had been described on the basis of their appearance, or physiognomy, and therefore in terms of one or several dominant species, as stated in the historical definition by the Göttingen botanist A. H. R. Grisebach (1814–1879) in “Ueber den Einfluss des Climas auf die Begränzung der Natürlichen Floren” [On the influence of climates on the discontinuities of natural floras]:
I would name phytogeographical formation a group of plants with a definite physionomic character like a meadow, a forest, etc. It is sometimes composed of an only species, sometimes of a complex of dominant species belonging to the same family, sometimes finally of a species aggregate which, although different, take on some common particularity in their organization; thus alpine meadows are almost exclusively composed of perennial grasses. (Linnea 12, p. 160)
This definition dates back to 1838, and would encourage research and controversies lasting almost a century. Indeed, being both rich and imprecise, it paradoxically played an important part in the evolution of plant community study, as plant sociology was born in the 1910s out of this work and scholarly confrontations. It is rich because it is derived from both the physionomic tradition that dates back to Humboldt’s geobotany, and the floristic tradition, in which plant groups are defined in terms of their floristic composition. If the formation had an essentially physionomical value for Grisebach, it was characterized by the dominant species, which does not necessarily determine the physionomy of the community, thus requiring a thorough floristic survey. Because of this very duality, Grisebach’s definition is also imprecise. Juxtaposing physionomy and floristics, it discouraged accurate distinction between formations (physionomical criteria) and associations (criteria gradually becoming floristic). To establish this distinction became more and more urgent during the nineteenth century as vegetation studies advanced. It was indeed most important to go beyond physionomical criteria, as they did not allow botanists to decisively distinguish between formations physionomically identical but floristically different—such as the tropical rain forests of Amazonia, Nigeria, and Malaysia.
The Importance of Characteristic Plants. In 1913 Josias Braun studied in Montpellier, attracted by the teaching of the renowned botanist-forester Charles Flahault (1852–1935). Braun had already published several scientific papers, including a contribution to the Flora des Graubündens (1904) and a study of the nival-level vegetation in Rhetic Alps—a massif of the Central Alps spreading over Switzerland (Grisons), Italy (Lombardia and Alto Adige), and Austria (Tyrol). He then, under Flahault’s supervision, began to write a doctoral thesis in which he studied the plant groups of southern Cévennes, in the south of France. But in this same year, he transformed the study of plant communities with publication of “Remarques sur l’étude des groupements de plantes” [Remarks on the study of plant groups], authored with another advanced student, Ernst Furrer (1888–1976) in the Bulletin de la Société Languedocienne de Géographie.
The authors broke the impasse between physiognomic and floristic approaches by stressing not only the importance of the complete floristic inventory of an association (an approach that had not yet been systematically explored), but also and above all the importance of the “character species.” Returning to a definition first proposed by Flahault and Schroeter at the Third International Congress of Botany (Brussels, Belgium, 1910), and according to which “The association ... is a plant group with a definite floristic composition and a uniform physionomy, growing in homogeneous station conditions” (Actes du III.e Congrès International de Botanique, p. 152), they added: “and possessing one or several character species,” which are “species almost exclusively localized in a given association” (Remarques sur l’étude des groupements de plantes, p. 21). Braun and Furrer acknowledged the limits of their point of view, as botanists are not able to distinguish all associations solely by means of character species when they are in the presence of mixed groups or associations. Therefore, they followed Flahault, who had recommended since 1900 that the study of the association include a complete floristic inventory. These “Remarques sur l’étude des groupements de plantes” had great repercussions, including the origin of the Zürich-Montpellier school.
Braun met Gabrielle Blanquet in Flahault’s laboratory where she was also studying botany. He married her in 1915, bearing from then on the name of Braun-Blanquet in accordance with a Swiss onomastic custom, in order to associate his spouse to his scientific activities. Back in Zürich in 1916, he became assistant to Eduard Rübel, then lecturer at the University of Zürich (1922–1926).
Although World War I had ruined botanical research in Europe, by 1925 a revised edition of the Vocabulaire de sociologie végétale (Plant sociology glossary) was published. The authors were Jules Pavillard (1868–1961), who was about to replace Flahault, and Braun-Blanquet. The first edition had been very rapidly translated into English, Polish, and Russian, illustrating its international reception. This publication was of interest historically as it expressed pedagogic intentions, a tangible sign of success in the development of a scientific theory.
Yet by 1926 conflicting opinions were evident. Leonid Grigorievitch Ramensky (1884–1953) and Henry Allen Gleason (1882–1975) linked the individuality of associations to the single plants that compose them, and particularly to seed scattering: Fortuitous but constant, scattering introduces species that should not be “normally” found in these associations. Hence, they considered heterogeneousness in the pattern of an association to be a coincidence; it was not to be considered a phenomenon inherent to natural vegetation dynamics, but the outcome of accidents or external environmental circumstances.
Between 1923 and 1927 Braun-Blanquet was Privat Dozent(a professor authorized to deliver free lectures) at the École Polytechnique Fédérale de Zürich. When he resigned from his post, Pavillard, who had replaced Flahault in 1927, immediately offered him the position of head of a laboratory in the Institute of Botany. In 1928, on Pavillard’s recommendation, the Faculty of Sciences Council granted him the right to teach in the University.
The Zürich-Montpellier School. In 1928, Braun-Blanquet published in Berlin his magnum opus: Pflanzensoziologie. The book was translated into English by 1932 and has been republished many times. Ecologists still refer to this comprehensive survey of theory and method. An important topic of the book was precisely the question of vegetation discontinuity, and focused on the minimal area, the area beyond which the number of new species met ceases to increase rapidly. Delimitation of the minimal area, through appropriate sampling methods, provides an objective basis for identifying a vegetation discontinuity: When the number of new species met again increases rapidly, the phytosociologist is in the presence of a new community.
The reasoning is schematically the following: The minimal area being far smaller than the analyzed community, the phytosociologist establishes floristic sample plots at least equal to the minimal area. Then he or she carries out, through various statistical methods, a floristic comparison of the samples from the community at issue. Certain species are found in every sample: This identifies them as constant species. Others show lower degrees of presence. When one compares samples belonging to different communities, one observes that certain species have a strong preference for particular groups. Such selective species are of great diagnostic value for the characterization of a community, and so are called “character species” (Becking, 1957, p. 444) because of their fidelity. This method is based on analysis of the entire species composition of a plant group.
The phytosociologist is then faced with the problem of their designation. Braun-Blanquet rejected the dominant species criterion, as the dominants are too often ubiquitous, and hence their presence is not ecologically informative. Moreover, as dominance is not necessarily linked with abundance, the criterion was considered too subjective, being physionomical in the final analysis. Braun-Blanquet finally chose the fidelity criterion. The association was therefore named after the character species (Charakterpflanzen), generally the most constant in a community. Following Schouw, the associations were named by the suffix -etum appended to the gender name of the character species, while the species name was written in the genitive: thus, the association characterized by the yellow flatsedge Cyperus flavescens L. was named Cyperetum flavescentis. The associations were grouped together in higher or lower taxa—that is, alliances, orders, and subassociations.
Braun-Blanquet’s system was quickly recognized in countries where it was hytogeographically suitable. The Cracow school developed on Zürich-Montpellier basis: Worked out in the Alps, the system could also be applied in the Tatras mountains. Within three decades the same phenomenon occurred in Hungary, Bulgaria, Czechoslovakia, Austria, the Netherlands, and Belgium. Indeed, in Europe—apart from Soviet ecologist Vladimir Nicolayevich Sukachev (1880–1967), who, like the Americans Henry Chandler Cowles (1869–1939) and Frederic Edward Clements (1874–1945), linked closely the slow variation of the Russian forest communities with gradual transitions in environmental factors—only the school of the Uppsala (Sweden) botanist Gustav Einar Du Rietz (1895–1967) developed an alternative approach to that of Braun-Blanquet. As Scandinavian and Arctic vegetation is relatively poor in species for a Zürich-Montpellier analysis, Uppsala phytosociologists elaborated a complex system founded on the analysis of a layered vegetation. Such an approach proved to be also appropriate in the uniform vegetation of the tropics. At the very beginning, Du Rietz defined the association as a vegetal society endowed with definite constant plants and physiognomy. This perspective was adapted to this terrain: In regions richer in species than Scandinavia, it would have revealed too many communities. It is indeed plausible that, at the time, numerous theoretical confrontations between schools of phytosociology were caused by the fact that researchers worked on different ground covers.
Foundation of SIGMA. How can historians of ecology assess the importance of Braun-Blanquet’s plant sociology in the elaboration of a systematic conception of plant communities? On the one hand, phytosociological groups have a significant ecological value: Through vegetation analysis and cartography, ecologists are able to pursue ever more accurate research on environmental factors. On the other hand, certain communities can be interpreted as indicators (sometimes of environmental gradients), and this was significant in ecological and agroecological researches during the interwar years. This is true of all phytosociological systems, but the success of the Zurich-Montpellier school has, if not overshadowed, at least relegated other systems to the background.
By 1929 Braun-Blanquet’s influence and activities were such that his laboratory had become obviously inadequate. The Scottish biologist and sociologist Sir Patrick Geddes (1854–1932) untangled the situation. He offered to Braun-Blanquet, for a symbolic rent, an entire floor of the Collège des Ecossais (Scots College), an international school for traveling scholars he had founded in Montpellier. This was the first headquarters of the Station Internationale de Géobotanique Méditerranéenne et Alpine (SIGMA), which eventually become known throughout the world among botanists. SIGMA was founded in 1930 by the Dutch botanist W. C. de Leeuw (1881–1964) and Raoul Combes (1893–1964), teacher of plant physiology at the Sorbonne (Paris). Braun-Blanquet was appointed director. It was financed by indirect international subsidies: Certain countries rented in the SIGMA space for their doctoral students or researchers and subscribed to the institution’s numerous scientific publications. After the death of Geddes, the rental lease could not be extended and the SIGMA had to be transferred to another site, acquired thanks to the generosity of another sponsor, Fritz Alleman von Albertini (1895–1971). Braun-Blanquet remained in charge of the SIGMA until he reached the age limit. After the death of his wife in 1966, his daughter, Mireille Braun-Blanquet, teacher at the Montpellier Faculty of Medicine, resumed the institution’s tradition of hospitality. The founder of the Zürich-Montpellier school died in 1980 at the age of ninety-six.
WORKS BY BRAUN-BLANQUET
With Ernst Furrer. “Remarques sur l’étude des groupements de plantes.” Bulletin de la Société languedocienne de Géographie (1913).
With Jules Pavillard. Vocabulaire de sociologie végétale. Montpellier, 1922.
Pflanzensoziologie. Berlin: Springer, 1928.
Plant sociology. Translated and edited by Henry S. Conard and George D. Fuller. New York: McGraw-Hill, 1932.
With L. Emberger and R. Molinier. Instructions pour l’établissement de la carte des groupements végétaux. Montpellier, 1947.
La végétation alpine des Pyrénées-Orientales. Etude de phytosociologie comparée. Barcelona: La Estación de Estudios Pirenaices y del Instituto Español de Edafologia, Ecologia y Fisiologia Vegetal, 1948.
“Essai sur la végétation du Mont Lozère comparée à celle de l’Aigoual.” Bulletin de la Societe botanique de France, 80e sess. extr. S.I.G.M.A., Com. 127, Tom. 100 (1953): 47–59.
Pflanzensoziologie, 3rd ed. Vienna: Springer Verlag, 1964.
Becking, Rudy W. “The Zürich-Montpellier School of Phytosociology.” The Botanical Review 23(7) (1957): 411–488. An essential reading.
Gleason, Henry Allan. “Braun-Blanquet’s Plant Sociology.” Ecology 14(1) (1933): 70–74. A rather critical look at the Zürich-Montpellier school of phytosociology.
Guinochet, Marcel. “Josias Braun-Blanquet (1884–1980).” Bulletin de la Societe botanique de France 129