Untersuchungen zur Pflanzensoziologie und Ökologie im Naturschutzgebiet Hohgant (Berner Voralpen)

Hegg, Otto (1965). Untersuchungen zur Pflanzensoziologie und Ökologie im Naturschutzgebiet Hohgant (Berner Voralpen). Beiträge zur geobotanischen Landesaufnahme der Schweiz: Vol. 46. Bern: Hans Huber

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A floristic analysis of the phytosociology of an area must, as a principle, use as f ar as possible floristic facts given within this area. That needs three steps of research:
1. determination of the sociological signification of all species
2. determination and description of the occurring plant communities
3. analysis of the interrelations between the communities ( ordination in a system), and eventually
4. comparison of the results of steps 1 to 3 - actually only valuable for the given area - with those of other areas.
The main purpose of the present paper lies on the often-neglected step 1: the sociological signification of every species within the total vegetation of the examined area as the only base of the subsequent work.
To find the sociological characterization of a species we made a statistical analysis. We compared the joint occurrences of all species in homogeneous, small relevés distributed in the whole working area (p. 34), numerically measured with the association index (Bindungsquotient)
D = number of relevés with both species / number of relevés with the rarer species of the pair
The determination of these association indices of all 231 species with all others considered in the analysis could be clone on an electronic computer.
Basing on all association indices we could draw a sociological schema in a polar coordinate system (Fig. p. 115). In this schema, any species has a fixed place according to its sociological signification demonstrated by its swarm of associated species (Bindungsschwarm, p. 36, Fig. p. 117-121), which gives a good characterization of the sociology of the species (p. 43). - Some species show high association indices to each other and similar tendencies in their swarms; they are called sociological groups. The total swarm of associated species of these sociological small groups (Kleingruppen) is used for the definition of the community type (p. 58 ff, Fig. p. 124-157). These are centers within the whole vegetation. They allow to group most of the stands, and most of the relevés can be related to them. They are the smallest units of vegetation definable with statistical groups and their swarm of associated species.
We consider this method as qualified and sufficient for the detection of all community types occurring in an area (p. 98). Fora separation of subordinate types other methods are needed, but the know ledge of the sociological significance of every species within the whole vegetation gives a good base.
The sociological schema contains also a sociological system. Some community types show ·more relations to each other (like the species of the small groups) and are related by a superior sociological group. That results in an ordination of the community types into a purely floristically defined sociological system, which shows nevertheless many facts concerning habitat.
The schema as it is drawn, in only two dimensions, is strongly abstracted. By using a third dimension (for every vegetation-zone an own schema, p. 104) it could ev. demonstrate the relationships between species and con1munity types in a better way, but it would be much less clear.
The resemblance of our results with those arrived at according to the methods of BRAUN-BLANQUET was shown on p. 100.
Besides this sociological research, we made some habitat-observations. In a great part of the relevés used for the statistical analysis we determined the pH of the uppermost horizon of the soil, a mathematic-astronomical index of the insolation (p. 11), height above sea level, exposition, inclination and the geological ground. For most of the described community types, we analysed a soil profile and determined pH, total content in organic matter, in carbonate, the electrical conductance of a soil extract (p. 17) and the colloidal dissolvable humus. These ecological results facilitate the description of the community types defined statistically and give a rough characterization of their habitat.

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