History and state of knowledge in phytosociology, and landscape phytosociology
The 2010 recurrence and celebrations of the phytosociology centenary, was an opportunity to trace the history and the evolution of this science (BIORET, 2010; GÉHU, 2010a,b, 2014; PIGNATTI, 2010; BIONDI, 2011). According to GÉHU (2011) vegetation sciences have their origins in the writings of Alexander VON HUMBOLDT (1805), considered as being the founder of the vegetation science for its descriptive analysis actually known of « Physiognomic » (or physionomic) type. He mentions, the Andean Cordillera landscapes, grouping plants communities in “societies” distributed attitudinally, according to the climatic gradients. In this context, von Humboldt was among the first scientists to recognize the ecological gradients, where species are replaced or altered in form along environmental gradients, such as a “cline” forming along a rise in elevation.
This “primordial” physiognomic approach tends very quickly to integrate two disciplinesŚ the phytogeography (FLAHAULT, 1901) and the plant ecology (REITER, 1885). From this multidisciplinary context, in ń8ř6, J. Paczoski replace the word “‑lorologie”, that he had created in ń8řń, by that of “Phytosociologie” (DASZKIEWICZ, 2004). Geographers, botanists, ecologists, geographers, cartographers and biologists have during this period discussed, evolved and placed strong bases on the sciences of vegetation and phytosociology. Between them we can mention: Beck, Binz, Blanc, Brunier, Cayer, Clements, Combres, Drude, Diels, Engler, Gadeceau, Ganong, Geiger, Ghiridon, Gradmann, Graebner, Grisebach, Harshberger, Hardy, Jaccard, Krassnoff, Leeuw, Litwinoff, Ludwig, Moss, Oliver, Schouw, Schimper, Tansley, Warming and Smith (DE WILDEMAN, 1910). The 1910s mark a turning point between the traditional phytogeography and the current phytosociology, with the definition of the plant association by Ch. Flahault and C. Schröter (GÉHU 2010a,b, 2014), and others proposals at the 1910 Brussels international congress of Botany (DE WILDEMAN, 1910), where the plant association was accepted as fundamental unit of the Synecology. The thesis of Braun-Blanquet (1915), focused especially on these study aspects representing a milestone in this science. According to VAN DER MAAREL (1975), PIGNATTI (1995); PIROLA (1999); CRISTEA et al., (2004); GÉHU (2006) and UBALDI (2012) we can assume that the modern Phytosociology takes place with the works of Braun-Blanquet which increase and elaborate the conceptual, methodological and typological framework basis and its applications (BRAUN-BLANQUET, 1915, 1921, 1928), establishing a Phytosociological school leading the International Station of Mediterranean and Alpine Geobotany “Station Internationale de Géobotanique Méditerranéenne et Alpine (SIGMA)”Ś a research center founded by W.C. De Leeuw and R. Combes initiative, and diriged by Braun-Blanquet from its foundation in 1930, until its disappearance in 1980 (GÉHU, 2010a). The ‐nglish version of this science name “Plant sociology” came from an American version of Braun-Blanquet book of Phytosociology (BRAUN-BLANQUET et al., 1932). This name was conceivably favoured by his collaborators of that book version (G.D. Fuller and H.S. Conard).
According to MOLINIER (1959, 1962) and BRAUN-BLANQUET (1964) the vegetation were approached statically for a long time, and the process of dynamics analysis rested on a fixist descriptive vision, often very subjective, emphasizing the difficulty of having a direct and complete perception of dynamics in plant associations during our lifetime, prejudices and others still critical issues (GUINOCHET, 1973; MUCINA, 2010).
From the 1970s, the context of classical Sigmatic Phytosociology (also called synphytosociology or landscape phytosociology) widens conceptually (RIVAS-MARTÍNEZ, 1976; BÉGUIN et al., 1979; TÜXEN, 1979; GÉHU & RIVAS-MARTÍNEZ, 1981; SCHWABE, 1989;
GILLET et al., 1991; THEURILLAT; 1992a, 1992b; LAZARE, 2009; BIONDI et al., 2011). Works multiplied worldwide, to improve the knowledge of the vegetation, and also the ways to do, supported by various critics, additions, proposals and adjustments based on different experiences related to schools and study areas. According to PEDROTTI (2013), from the same period, studies of plant communities mainly take novelty within the integration of vegetation dynamics in time and space (TÜXEN, 1973, 1978; FALISKI, 1986, 1998, 1999; FALISKI & PEDROTTI, 1990). The dynamico-catenal phytosociology has made possible to better integrate vegetation dynamics by describing more finely the trajectories of vegetation series.
Phytosociology, plant map and the dynamico-catenal approach
Phytosociology is the science of plant communities, so the plant sociology. The basic studies unit of the classic phytosociology is the « plant association » (also called Phytoassociation), that constitutes a homogeneous plant community in a homogeneous environmental unit (floristically homogeneous community in a ecological homogeneous surface). The Phytoassociation constitute the first level analysis of the plant landscape, according to GÉHU (1986, 1991a, 2006b). Plant association directional dynamics is then considered when progressive (such as: primary or secondary succession and regeneration) and regressive directions (such as: degeneration, and regression) in terms of time sequence. The former are conceived to tend from actual condition toward the hypothesized higher environmental equilibrium; the latter on the contrary tend to move away from this higher equilibrium (FALISKI, 1986, 1991, 1994, 1999).
Recalling BRAUN-BLANQUET (1915) the plant Association is a plant community, more or less stable (non static, but in terms of clear identity and repeatability), and in equilibrium with the environment. Thus, it will be characterized by a determined floristic composition in which certain exclusive elements, or almost the characteristic species, reveal by their presence aparticular and autonomous ecology. Braun-Blanquet continued that the in-depth study of plant associations have to take into account all the synecological phenomena and consider each association from every point of view. The description must be followed by an ecological part including the enumeration of the biological forms, of the biology, geography, genetic and other characteristics which include the origin and the evolution of the plant assemblages (grouping, community…). Thus, contemporary phytosociology is the science of plant groupings, that is to say, syntaxa (GÉHU 2014).
Bio-evaluation, biodiversity and heritage assessment of the vegetation
Bio-assessment is the assessment of the ecological or environmental quality of an environment or ecosystem, based on ecological or biological criteria » (DA LAGE & MÉTAILIÉ, 2015). It brings together all the methods and techniques that allow an evaluation of the different elements of the environment, and which can contribute to a hierarchy of natural heritage and decision support tools (BIORET et al., 2009). We can divide bio-assessment following the natural-cultural heritage value, the productivity and products of an agro-ecosystem, the anthropization/wilderness, or just the quality in terms of pollution, species or community’s presence…. The assessment type and monitoring depends a lot to what is the level of reference (i.e.: ecosystem, landscape, species and plant community of reference). Within any level the bio-evaluation depends also on the environmental values choice and to the reference choices (number of species per unit area; number of communities per unit area; number of genotypes per unit area; wilderness; productivity; pollution; urbanization; flowering or other aesthetic factors; cultural-historical issues; perception or affection…). The environmental quality of a plant landscape can be assessed by using one or more criteria such as naturalness (or conversely, artificialization), resilience, threats, rarity, diversity…).
The same land could have a positive and negative feedback at the same time depending on evaluation choices and observer subjectivity. For that ways the bio-assessment techniques had some critics and evolution during the time, leading to the proposal of new indices or evaluation scales: trying to establish more objective criteria and status of references .
Following the previous authors, we can assume that in the field of plant landscape bioassessment,
the dynamico-catenal phytosociology proves to be a useful tool to bring essential information to the territory planning and allowing the implementation of land plans, conservation and management, programs thanks to its predictive nature based on phytoassociation and series (LOIDI, 2008). According to GÄRDENFORS et al. (2001) and IUCN species redlists, generally the vegetation biodiversity assessment mainly focuses on rare species presence. In any case, the species related criteria (scarcity, threats, uses, appearance…) could also be applied to higher levels of plant organization, for the elaboration of red lists of plant communities at many levels. From plant communities (RODWELL & COOCH 1998), including phyto-associations (GÉHU, 1991c; BIORET et al., 2011; LAZARE, 2013b), synusiae to biotopes and complexes of biotopes (BLAB, et al., 1995; HELCOM, 1998).
Table of contents :
1.3 The CarHAB Project framework
1.4 Research questions and hypotheses
2 – GENERAL CONCEPTS AND PRINCIPLES
2.1. History and state of knowledge in phytosociology, and landscape phytosociology .
2.1. Vegetation and mapping principles
2.1.1. Phytosociology, plant map and the dynamico-catenal approach
2.1.2. Terroir and Territory biogeographical definition
188.8.131.52. Large territories
184.108.40.206. Small territories
2.2 Vegetation mapping of plant complexes
2.2.1 Plant communities between small and large scales
2.2.2 Integrated plant mapping approach
2.2.3 Bio-evaluation, biodiversity and heritage assessment of the vegetation
2.3 Principles of geography, morphology and other ecological aspects of Estuaries
2.3.1 Main geographical and abiotic aspects
2.3.2 Morphological types
2.3.3 General ecological and synecological aspects
2.3.3 Global environmental risks, natural resources, human ecology, land uses, and threats
3. STUDY AREA
3.1. Atlantic French Estuaries
3.1.1. General description
220.127.116.11. Location and distribution
3.1.3 Principles and State of knowledge on vegetation
3.1.4 Human impact, modification of land forms, and historical uses
3.2 General description per Estuary
3.2.1 Largest estuaries
3.2.2. Smaller estuaries
18.104.22.168. Brittany estuaries
22.214.171.124 Other estuaries
126.96.36.199.1 The Hâvres of Cotentin (Lower Normandy)
188.8.131.52.2 Estuaries from Picardie and Nord-Pas-de-Calais
184.108.40.206.3. Other estuaries of Aquitaine
4.1. Main bioclimate, biogeography and abiotic aspects
4.1.2. Ombrothermic diagrams
4.2. Plant landscape methodology
4.2.1 Methodological approach to define vegetation series and vegetation series complexes
4.2.2. Potentiality, phytodynamics and vegetation tendencies analysis
4.2.3. Field relevés
4.2.4. Transect pointing and spatialisation
4.3. Cartography, generalization, modeling and extrapolation
4.3.1. Time and surface scale
4.3.2 The scale problem and resolution factor
4.3.3. Sampling: choice of test points, relevés, synrelevés/géosynrelevés, and transects .
4.3.4. Mapping series and geoseries according to the dynamico-catenal approach
4.3.5. Semiotics: the choice of colors in plant mapping
4.3.6. Map restitution and the geographic information system
5. DATA ANALYSIS AND RESULTS
5.1. Theoretical Ecological compartments scheme of an estuary
5.2. Bioclimate mapping
5.2.1. Bioclimatic map of Atlantic phytoregion
5.2.2. Bioclimatic characterization of selected estuaries
5.2.3. Ombrothermic diagrams of estuaries
5.3.1. Table of associations, and plant groupments
5.3.2. Description of plant associations
5.4. Synphytosociology and Geosynphytosociology
5.4.1. Series description
5.5. Plant communities’ diversity and organization
5.6. Vegetation models
5.6.1. Vegetation Series maps
220.127.116.11. Aulne estuary
18.104.22.168. Laïta estuary
22.214.171.124. Loire estuary
5.6.2. Transects from minor to major River bed
5.7. Theoretical Series/Catenas scheme of an estuary
6.3.4. Plant landscape representation at smaller scale
7. CONCUSION AND OUTLOOKS