Storia del paesaggio vegetale e dell’impatto antropico nell’area del Gran Sasso d’Italia (Abruzzo) in base a polline, palinomorfi non pollinici e microcarboni (sondaggi di Piano Locce 1225 m slm)

The study presents a palaeoenvironmental reconstruction based on pollen, no-pollen palynomorphs (= NPPs) and microcharcoals analyses on samples of two cores (PL1 e PL2) taken at Piano Locce ( 1225 m a.s.l., Barisciano, L'Aquila - Italy), within a multidisciplinary programme. Piano Locce is a tectono-karstic depression on the southern side of the “Massiccio del Gran Sasso d’Italia” mountain and it is a hollow that trapped the sediments eroded from the soils of the sorrounding mountains and the wind carried pyroclastic ashes. Methods – Core PL1, drilled in 2003, 80 m long without reaching the limestone at the base, was sampled for pollen analysis following the stratigraphy to obtain an ample vegetational/climatic reconstruction. Core PL2, drilled in 2008, 10 m long, was sampled approximately every 5-10 cm to obtain a detailed reconstruction of the floristic-vegetational/climatic events and of human impact during the Late Pleistocene and the Holocene. For this study 91 of the 260 samples taken from the two cores were studied: 10 from PL1 core (from 0 to 5.14 m) and 81 from PL2 core. The finds analysis, the data exposition and the results interpretation principles followed the current standards. For microcharcoals a particle-count method that divides them in 5 classes was carried out. Chronology – Two datings based on chemical analysis of volcanic minerals are available: core PL1 is dated 170.000-200.000 years BP at the bottom and core PL2 is dated 36.000 years BP at 5 m depth. Results, Discussion, Conclusions – Pollen analysis of Piano Locce series (46.150 pollen finds in the two cores) provides the history of vegetal landscape from 36.000 years BP, plus former data. The finding of high percentage of Artemisia pollen, with Chenopodiaceae and Poaceae and low percentage of arboreal plants suggests, for the lower part of the sequence, a steppe vegetation environment referable to the Last Glacial. In this part some zones may be included in the Last Glacial Maximum (minimum of woody plants pollen), in the interstadial Bolling-Allerod (low Artemisia, relative increase and differentiation of trees/shrubs) and in the Younger Dryas (arboreal plants decrease and Artemisia rise). The transit from the Last Glacial to the Holocene is testified by an arboreal plants increase and the affirmation of mixed Oak-wood (at about 1.50 m depth in PL2). Data suggests that in the area a grass-land grazed quite precociously persisted during the time. Wood always remained far from Piano Locce depression and it was formed alternatively by conifers and broadleaves and subsequently by the predominance of Oak-wood broadleaves. Beech-wood is little represented, probably due to local climatic factors. The combination of Cultivated/cultivable plants begins to be significant in the Medium Holocene and it is obvious in the Upper Holocene. This is testified by Castanea, Juglans, Olea, Vitis e cereals. Prunus dulcis was found in the most superficial samples. NPPs (1.797 finds identified in PL2 core) in the Upper Pleistocene show mainly algal microremains (Pediastrum and Botryococcus colonies and Spirogyra spores) attesting a lacustrine sedimentation, while coprophilus fungi spores appears in good percentage during the Holocene, in a terrestrial environment with periodical water puddles. This fungi presence, like Sporormiella-type, Sordiaria-type, Apiosordiaria and Valsaria-type, in levels caracherized by Cichoriodeae, Asteroideae, Cirsium-type, Galium-type, Ranunculaceae, Stellaria-type pollen suggests the hypothesis that Piano Locce depression was exploited as a grazing area, first by wild animals, then by domestic ones. Microcharcoals (analyzed in PL2 core) are less represented in the lower part of the sequence, maybe due to the presence of humans living in caves and shelters settled in areas at lower quotes than Piano Locce. The presence of bigger sized particles testifies nearer fires, natural or caused by the hunter-gatherers that hunted in the area. During the Holocene the sum of microcharcoals increases, according to the evidence of anthropization provided by pollen and no-pollen palynomorphs.