Reconstruction of the mid-to Late- Holocene history of vegetation and land- use in Petresiunai, north-east Lithuania: Implications from palaeobotanical and archaeological data

摘要

This study presents the results of multi-proxy investigations of mid-to late-Holocene vegetation dynamics and land-use history associated with the Petresiunai archaeological site, north-east Lithuania. Identified vegetation changes are discussed in the context of both natural and anthropogenic factors determined within the site and its surroundings. The initial stages of colonisation and the subsequent land-use dynamics are discussed by applying the results of biostratigraphical and archaeological-historical data. To explore these issues, a lacustrine sediment core obtained from the stand-scale sedimentary basin was studied using a microbotanical (pollen and microcharcoal) survey and C-14 and magnetic susceptibility (MS) measurements. Associations between proxies were statistically tested. In addition, archaeological excavations were conducted within the area of the Petresiunai hill fort. The results obtained show the presence of a heavily forested landscape with broad-leaved deciduous trees dominating the taxa existed in the area until approximately 4800-4700 cal BC. Low magnitude fire activity mainly caused by the natural factors was recorded. The expansion of spruce and the gradual decrease in thermophilous taxa suggests a local-scale climatic reversal started prior to the general decline of the HTM (Holocene Thermal Maximum). The decay of broad-leaved taxa followed by the pronounced culmination of Picea-dominated forest (2100-1500 cal BC) confirms the general re-organisation of the forest structure in the area. A small-scale vegetation stress, accompanied by an increase in fire interference suggestive of episodic Neolithic-Bronze Age human activity, was noted in the area at approximately 2800-2200 cal BC, 1800 cal BC and 1500 cal BC. Biostratigraphical and sedimentological data suggest agriculture practices and animal husbandry were introduced and the landscape was increasingly utilised between 1300 and 1000 cal BC, which preceded the archaeological record of the Petresiunai hill fort by a few hundred years. However, as indicated by pollen data, pastoral farming predominated the local economy until approximately 400 AD. The establishment of regular cultivation practices, including crop rotation, and the formation of permanent fields with introduction of winter cereals began in the surroundings of Petresiunai by the 6th - 7th c. AD. At that time, the secondary open Betula-dominant vegetation successions flourished in the area. A highly diversified landscape with large agriculture fields, open grounds, meadows and pastures culminated in the area between 1000 and 1300 AD. After this period, the intensity of the human-induced vegetation changes apparently decreased, which confirms re-organisation of the settlement pattern and land-use in this area.