Considérations sur la distribution structurale d'un peuplement de pin sylvestre d'un marais oligotrophe (Roumanie)

Summary

In the present paper the authors are undertaking to show the correlation that exists, between the age, density of the trees and the coefficient of aggregation of a population of pines studied in the Lucs bogs-reservation of the Harghita Mountains (Rumania). The pines which have been studied are relics and a number of arctic elements (Sparganium minimum, Potamogeton alpinus, Betula nana) had survived with them. A geobotanical survey showed that the micro-distribution of the pine population presents, in spite of the uniformity of the ecological and phytosociological conditions, fluctuations of density as well as of aggregation which thus reflect the existence of some intense phytosociological processes in the apparently stationary structure of the trees. The coefficient of aggregation of the population under study has been determined by the Hopkins-method, based on some linear measurements carried out between the points determined at random (by chance) and the nearest vegetal individuals as well as between pairs of individuals chosen at random.

The measurements have established that the structure of the trees which presented initially an aggregated dispersion, evolve together a natural elaquating towards the achievement of a normal dispersion. The calculation of the entropy of spatial distribution based on a determination of the probability of frequency of each of the calculated distances shows a significant growth of the entropy of spatial distribution of the constituent elements; this shows that the spatial structure of the population analysed evolves towards the stage of the highest probability, this being identical with the condition of statistical stability in which, however, the evolution of phytosociological processes continued.