Description: We report the first findings of coexisting early Holocene Hässeldalen and Askja-S cryptotephras in a varved sediment record in Lake Czechowskie (Poland). A time span of 152 +11/−8 varve years between the two tephras has been revealed by differential dating through varve counting. This is in agreement within the uncertainties with calculations from radiocarbon-based age models from the non-varved Hässeldala port record in southern Sweden, but shorter than assumed from the non-varved lake record on the Faroe Islands. We discuss possible reasons for the observed differences in duration between the two tephras and provide a revised absolute age for the Askja-S tephra of 11 228 ± 226 cal a BP based on anchoring our floating varve chronology to the absolute timescale by using the Hässeldalen Tephra as dated in the Hässeldala port sediments (11 380 ± 216 cal a BP). This age agrees with radiocarbon age models with larger uncertainty ranges, but is slightly older than radiocarbon-based age models with narrow uncertainty bands and is even 200–300 years older than the age reported from the Faroe Islands record. In addition to these chronological issues we discuss the possible response of the Czechowskie sediment record to the Preboreal climate oscillation.

Description: High-resolution biological proxies (pollen, macrofossils, Cladocera and diatoms), geochemical data (μ-XRF element scans, TOC, C/N ratios, δ18Ocarb and δ13Corg values) and a robust chronology based on varve counting, AMS 14C dating and tephrochronology were applied to reconstruct lake system responses to rapid climatic and environmental changes of the Trzechowskie palaeolake (TRZ; Northern Poland) during the late Allerød – Younger Dryas (YD) transition. Palaeoecological and geochemical data at 5–15 years temporal resolution allowed tracing the dynamics of short-term shifts of the ecosystem triggered by abrupt climate change. The robust age control together with the high-resolution sampling allowed the detection of leads and lags between different proxies to the climate shift at the Allerød-Younger Dryas transition. Our results indicate (1) a water level decrease and an increase in wind activities during the late Allerød and the Allerød-YD transition, which caused intensified erosion in the catchment, (2) a two-decades delayed vegetation response in comparison to the lake depositional system. Comparison with the Lake Meerfelder Maar record revealed slightly different vegetation responses of the Trzechowskie palaeolake at the YD onset.

Description: Late glacial and Holocene environmental history of Lake Łukie and its catchment is reconstructed from the lake sediments. This shallow lake is situated in the marshy Polesie region in eastern Poland. Sediments began to accumulate in the lake in the Older Dryas. On the basis of macrofossils, pollen, and Oribatida remains, and with the use of Kohonen's artificial neural network (self-organising map, SOM), six stages (corresponding to subclusters X1, X2, X3 in cluster X, and Y1, Y2, Y3 in cluster Y) of the lake history were distinguished, and indicator taxa of each stage were identified from the indicator value (IndVal) index. During the transition period corresponding to the border between X and Y, the ecosystem transformed in the broad sense from the protocratic to mesocratic phase in a 5-point scale transformation of the landscape in the glacial–interglacial cycle. All the steps involved in post-glacial history succession during interglacial cycles include changes in climate, soil, and biotic interactions. Indicator taxa for the subsequent SOM subclusters X1, X2, and X3 are associated with the first phase of the protocratic glacial–interglacial cycle. The transformation that occurs on the level of cluster Y (subcluster Y1) is the mesocratic phase (ca. 9000–5000 14C age BP), which is characterised by high temperatures and development of closed forest (climax forest). Subcluster Y2 corresponds to the transformation of forest cover during the oligocratic phase (ca. 5000–3000 14C age BP), which is associated with decreasing forest share and deteriorating soils. Finally, subcluster Y3 can be associated with the telocratic phase, characterised by the influence of a more oceanic climate (from ca. 2500 14C age BP) with declining temperatures, higher humidity, and milder seasonal contrasts, which contributed to the development of more open vegetation and infertile soils. This stage also corresponds to an increased human activity and landscape transformation, such as from forests to cornfields and from wetlands to meadows. Interestingly, the currently strictly protected brittle naiad (Najas minor) was present in the lake during the Atlantic, Subboreal, and Subatlantic periods; however, this species is not listed as being part of the present vegetation and may have become extinct relatively recently.

Description: While of higher plant origin, a specific source assignment of sedimentary leaf wax n-alkanes remains difficult. In addition, it is unknown how fast a changing catchment vegetation would be reflected in sedimentary leaf wax archives. In particular, for a quantitative interpretation of n-alkane C and H isotope ratios in terms of paleohydrological and paleoecological changes, a better understanding of transfer times and dominant sedimentary sources of leaf wax n-alkanes is required. In this study we tested to what extent compositional changes in leaf wax n-alkanes can be linked to known vegetation changes by comparison with high-resolution palynological data from the same archive. We analyzed leaf wax n-alkane concentrations and distributions in decadal resolution from a sedimentary record from Trzechowskie paleolake (TRZ, northern Poland), covering the Late Glacial to early Holocene (13360–9940yrBP). As an additional source indicator of targeted n-alkanes, compound-specific carbon isotopic data have been generated in lower time resolution. The results indicated rapid responses of n-alkane distribution patterns coinciding with major climatic and paleoecological transitions. We found a shift towards higher average chain length (ACL) values at the Allerød–Younger Dryas (YD) transition between 12680 and 12600yrBP, coevaled with a decreasing contribution of arboreal pollen (mainly Pinus and Betula) and a subsequently higher abundance of pollen derived from herbaceous plants (Poaceae, Cyperaceae, Artemisia), shrubs, and dwarf shrubs (Juniperus and Salix). The termination of the YD was characterized by a successive increase in n-alkane concentrations coinciding with a sharp decrease in ACL values between 11580 and 11490yrBP, reflecting the expansion of woodland vegetation at the YD–Holocene transition. A gradual reversal to longer chain lengths after 11200yrBP, together with decreasing n-alkane concentrations, most likely reflects the early Holocene vegetation succession with a decline of Betula. These results show that n-alkane distributions reflect vegetation changes and that a fast (i.e., subdecadal) signal transfer occurred. However, our data also indicate that a standard interpretation of directional changes in biomarker ratios remains difficult. Instead, responses such as changes in ACL need to be discussed in the context of other proxy data. In addition, we find that organic geochemical data integrate different ecological information compared to pollen, since some gymnosperm genera, such as Pinus, produce only a very low amount of n-alkanes and for this reason their contribution may be largely absent from biomarker records. Our results demonstrate that a combination of palynological and n-alkane data can be used to infer the major sedimentary leaf wax sources and constrain leaf wax transport times from the plant source to the sedimentary sink and thus pave the way towards quantitative interpretation of compound-specific hydrogen isotope ratios for paleohydrological reconstructions.

Description: In recent decades, it has been observed that most forest fires in Europe were caused by people. Extreme droughts, which are more often prolonged, can increase the risk of forest fires, not only in southern Europe but also, in Central Europe. Nonetheless, catastrophic fire events are not well recognized in the Central European Lowlands (CEL), where large forest complexes are located. Knowledge of past fire activity in this part of Europe is scarce, although several fires have occurred in this area during the previous millennia. Large coniferous forest monocultures located in the CEL are highly susceptible to fires and other disturbances. Here, we present a case study from the Tuchola Pinewoods (TP; northern Poland), where large pine monocultures are present. The main aim of this study is to document the potential effects past land management has on modern day disturbance regimes using state-of-the-art paleoecological data, historical documents and cartographic materials. We then present a protocol that will help forest managers utilize long-term paleoecological records. Based on paleoecological investigations, historical documents, and cartographic materials, our results show that, in the past 300 years, the TP witnessed not only disastrous fires and but also windfalls by tornados and insect outbreaks. A change in management from Polish to Prussian/German in the 18th century led to the transformation of mixed forests into Scots pine monocultures with the purpose to allow better economic use of the forest. Those administrative decisions led to an ecosystem highly susceptible to disturbances. This article provides a critical review of past forest management as well as future research directions related to the impacts of fire risk on land management and ecosystem services: (a) habitat composition and structure (biodiversity); (b) natural water management; and (c) mitigation of climate changes. Designated forest conditions, management, and future fire risk are a controversial and highly debated topic of forest management by Forestry Units. More research will allow the gathering of reliable information pertinent to management practices with regard to the current fire risks. It is necessary to develop a dialog between scientists and managers to reduce the risk of fires in projected climate change.