Illustrazione ed Esemplificazione sui Querceti delle Langhe di un Metodo Biocenotico Proposto da e. Schmid

Summary

The A. describes a biocoenological method, proposed by E. Schmid, applying it to the study of Quercus communities of the Langhe (southern Piedmont.)

Two fundamental notions are placed as a basis for the method, viz.; the vegetation belt, a notion of chorological nature, defined and introduced by E. Schmid in 1936, and the biocoenosis, a notion of biocoenological nature, proposed by Möbius in 1877 and successively applied to the study of plant communities, or phytocoenosis. Both the notions are shortly illustrated and discussed by the A.

The main purposes of the method are; to build up models of the phytocoenosis, to which the concrete objects of the research, viz the plant communities in nature, may be referred to; to show the boundaries and the gradual transitions among different phytocoenosis, through the comparison of their respective models; to refer the phytocoenosis to the vegetation belts.

It is first of all, necessary to establish the floristical pattern of the phytocoenosis and then to analyse every species as follows:

Floristical analysis. By examination of the taxonomic position, of the phylogenetic, genetic, chorological and epiontological characters, a floristical species-pattern is built up for every species; with similar species-patterns, floristical types are built up, which are then recorded in a spectrum (spectrum of floristical types); by means of this spectrum the phytocoenosis may be referred to the vegetation belts.

Ecological analysis. For every species the morphological characters are examined, the requirements of light, temperature and humidity, the nutrition, the ways of propagation, the spreading out of seeds and fruit, the abiotical enviromment, the special correlations and the antropogenical influences are recorded. Such an analysis gives ecological species-patterns, by which ecological types are formed; the latter are recorded in a spectrum (spectrum of ecological types).

Biocoenological analysis. In the plant communities to be studied, a square area is choosed; the initial area is gradually enlarged, till the curve constructed with the relation between the numbers of the species and the sizes of the squares turns into the horizontal line (in many instances an area 25 mq. wide is sufficient); the square area choosed is subdivided in little squares with a side of 20 cm.; the species found in every little square are recorded. The technique described allows an exact recording of the structural peculiarities of the studied area and the getting of very exact frequency values for every species.

With the spectra of the floristical and ecological types the models of the phytocoenosis are built up, by which the differentiation of the phytocoenosis is allowed and the transitions and fluctuations in the structure of vegetation, may be followed.

Having applied this method to the study of Quercus communities of the southern Langhe, the A. thinks to be entitled to come to the following conclusions: α) the studied phytocoenosis belongs to the marginal parts of Quercus pubescens vegetation belt and more precisely to that part, where Quercus pubescens and Quercus Tilia Acer vegetation belts are overlapping; the Quercus communities of the northern Langhe instead, are to be referred to Quercus Tilia Acer vegetation belt. The existence of a gradual structural transition from the phytocoenosis of the central parts of the area of Quercus pubescens vegetation belt to the marginal ones, may be pointed out; the studied phytocoenosis is to be considered as a term of such a transition.