Hydrological variability of middle European peatland during the Holocene, inferred from subfossil bog pine and bog oak dendrochronology and high-resolution peat multiproxy analysis of the Budwity peatland (northern Poland).

Subfossil pine and oak tree trunks were excavated during exploitation of the Budwity peatland in Northern Poland. Based on dendrochronological analysis, the woodland successions in peatland were reconstructed and correlated with moisture dynamics of the peatland ecosystem inferred from the high-resolution multi-proxy analysis of the peatland deposits. From the results of dendrochronological analysis and the 14C wiggle matching methods, four floating pine chronologies (5882-5595; 5250-5089; 3702-3546; and 2222-1979 mod. cal BP) and two oak chronologies (4932-4599 and 4042-3726 mod. cal BP) were developed. The organic sediments of the peatland (6 m thick) were deposited over approximately nine thousand years. The lower complex (525-315 cm) comprises minerogenic peat, while the upper complex (315.0-0.0 cm) is composed of ombrogenic peat. Subfossil tree trunks are distributed across various peat horizons, which suggests multiple stages of tree colonisation followed by subsequent dying-off phases. Multiproxy sediment analyses (lithological, geochemical and δ13C stable isotope, pollen, plant macrofossils, Cladocera, diatom, and Diptera analyses) indicate that the two earliest phases of pine colonisation (5882-5595 and 5250-5089 mod. cal BP) and the two stages of oak colonisation (4932-4599 and 4042-3726 mod. cal BP) were associated with periodic drying of the peatland. Conversely, tree dying-off phases occurred during periods of increased water levels in the peatland, coinciding with stages of increasing climate humidity during the Holocene. The two most recent phases of pine colonisation occurred during the ombrogenic stage of mire development. Remnants of the dead forest from these phases, marked by subfossil trunks still rooted in the ground, were preserved and exposed presently during peat exploitation, approximately 2.5 m below ground level. The identified phases of tree colonisation and subsequent dying-off phases show correlation with analogical phenomena observed in the other investigated European peatlands.

Changing natural conditions and their impact on the Mt. Snieznica landscape, Outer Western Carpathians - Reconstruction of the Holocene environment based on geochemical indices and radiocarbon dating.

Environmental changes during the Holocene impacted the development of all civilizations, and it is important to understand the power of this influence through, for instance, the reconstruction of these changes. However, when the climate and environmental conditions of the deep past are analyzed, researchers need to rely on various types of proxy data that are only approximations of the required information. In addition, this type of information is often absent or has several gaps (hiatuses). In the present study, we analyzed a 4.4-m deep core excavated from the fen formed within the landslide body on the northern side of Mt. Snieznica in the Wyspowy Beskidy Mountains, the Outer Western Carpathians, southern Poland. In total, we analyzed 405 samples in terms of 29 geochemical components (e.g., nitrogen (N), carbon (C), sulfur (S), and the total organic carbon (TOC)) and physical properties, namely particle-size distribution, loss on ignition (LOI), and microcharcoal content. Additionally, to establish geochronology, we dated 27 samples of different biological materials using the Accelerator Mass Spectrometry radiocarbon method. A detailed examination of plant macrodetritus and wood anatomy supported our interpretation based on the geochemical data. The Mt. Snieznica landslide probably formed ca. 14,000 cal BP in the first phase of the Allerød Interstadial. For almost 9000 years, there were no appropriate terrain conditions for the long-term accumulation of organo-mineral materials. At ca. 4400 cal BP, peat accumulation commenced. The beginning of peat accumulation correlates with the global 4.2 Bond event of cold climate conditions. After another ca. 2000 years, the core sediments were dominated by limnetic mud, suggesting aquatic conditions in the landslide depression. This sudden shift in the characteristics of sedimentation is loosely linked to the boundary between the Subboreal and Subatlantic phases (ca. 2500 cal BP). The apparent dichotomy of the depositional record agrees with the reconstructed climatic conditions during the second part of the Holocene. Up to 3000 cal BP, the regional climate was warm and humid, which allowed fast biomass production and hillslope stabilization by trees. Forest fires occurred only at the beginning and end of this period (4400-3000 cal BP). After 3000 cal BP, the regional climate became cool and dry. In this period, we found evidence of intensified erosion, but it was unrelated to forest fire activity.