Reconstruction of vegetation transects for the Messinian–Piacenzian of Italy by means of comparative analysis of pollen, leaf and carpological records
Abstract The first comprehensive and comparative analysis of the main micro (pollen) – and macro (leaves, fruits and seeds) – palaeobotanical data from northern and central Italian sites, allows four transects of ancient vegetation for the Messinian to Piacenzian interval to be constructed. Standard criteria for the reconstruction of vegetation transects are established, so that our approach could be extended to other basins or regions bearing Neogene palaeofloras, and would permit readily comparable reconstructions of past vegetation to be obtained. Messinian to Piacenzian lowland plant communities, as reconstructed by means of this integrated and standardized approach, show the dominance of warm temperate forest taxa in northern and central Italy, with the highest floristic affinity to present day forests of the eastern part of central China. Some panholartic conifers, usually interpreted as “cool temperate” taxa in Neogene assemblages, are assigned to the upland vegetation; they are scarcely represented in Messinian and Zanclean pollen records (with the exception of some intervals characterized by increases in Picea and Cedrus ) and almost completely lacking in leaf and carpological ones; during the Piacenzian, notably from 2.8 Ma, the pollen percentage of such taxa, in particular Picea , progressively increased. The overall scantiness of non-aquatic herbs, not only in the macrofossil record, but also in the pollen one, indicates the absence of dry conditions and excludes long-lasting expansion of open vegetation. The type of vegetation (“subtropical humid forest”) reconstructed for the evaporitic Messinian (ca. 5.9 to 5.6 Ma) suggests that the Adriatic-Padane basin would have been under predominant moist conditions, even during the deposition of evaporites. Slightly drier phases in the post-evaporitic Messinian are suggested at first by the short period of increase of Lygeum , a steppe plant, close to 5.5 Ma, then by the ecological preferences of some unusual macrofossil taxa ( Cupressus , Medicago , Vitex ). These are, however, still associated with arboreal plants which require humid conditions, definitely indicating that forested environments persisted (“subtropical sub-humid forest”). The Zanclean and Piacenzian transects are extremely similar to the evaporitic Messinian one, and the mesic lowland (zonal) vegetation can still be defined as “subtropical humid forest”.