Determination of the nutritional state of soils by means of the phytosociological method and different statistical techniques (Bayesian statistics and decision trees) in Spain

The paper deals with the nitrophilous Hordeum leporinum pasture- lands peculiar to the olive groves of Jaén, Spain. The study first selects physio- gnomically homogeneous land plots and subsequently samples are taken where the relevant species is dominant. Simultaneously, an edaphic sample is taken and the different edaphic parameters are analysed. By means of phytosociologi- cal and statistical methods (cluster analysis) and co—location networks, we describe a new association, namely Anacyclo clavati—Hordeetum leporinum. With the aid of advanced statistical techniques and Bayesian networks, we carry out different analyses in order to find out plant—soil correlations, in particular, for Filago lutescens and Hordeum leporinum. The paper also provides a decision tree for Hordeum leporinum. In this decision tree the values of the different eda- phic parameters are checked against the values of the abundance—dominance index.