Ecological and Syntaxonomic Analysis of <i>Pinus halepensis</i> Mill. in the Iberian Peninsula and Balearic Islands

This work aims to review the natural communities of <i>Pinus halepensis</i> in Spain. The methodology consisted of subjecting 400 phytosociological relevés to georeferencing and statistical, biogeographical, and bioclimatic treatment. We analyse the communities of <i>Pinus halepensis</i> on the Iberian Peninsula and Balearic Islands. Five syntaxa with association rank are described in several works and included in the alliances <i>Rhamno-Quercion</i> and <i>Oleo-Ceratonion</i>. <i>Ephedro-Pinetum halepensis</i> was initially proposed as a community by Torres et al. and subsequently raised to the rank of association by Rivas-Martínez et al. In this work, we have separated the plant communities dominated by <i>Pinus halepensis</i>, which was previously included in other syntaxa, and as a result, we propose four new associations and a new alliance for the Iberian Peninsula: ass. <i>Bupleuro rigidi-Pinetum halepensis</i>; ass. <i>Ephedro nebrodensis-Pinetum halepensis</i>; ass. <i>Rhamno angustifoliae-Pinetum halepènsis</i>; ass. <i>Rhamno laderoi-Pinetum halepensis; all. Rhamno lycioidis-Pinion halepensis</i>. In view of the fact that some of the communities have been published as edaphoxerophilous and climatophilous, we suggest separating the climatophilous from the edaphoxerophilous character in the diagnosis of the communities, and have therefore recently proposed the ombroedaphoxeric index I_oex (I_oex = P_p − e/T_p × CR), which considers positive precipitation P_p, positive temperature T_p, residual evapotranspiration (e), and water retention capacity CR (0.25, 0.50, 0.75). In conclusion, we propose the associations mentioned above, which will allow the implementation of a reforestation treatment in accordance with the natural environment.