Stratygrafia pyłkowa i historia roślinności interglacjału mazowieckiego i starszej części zlodowacenia liwca w zachodniej i środkowej części Wyżyn Polskich

Abstract

The goal of this work is to analyse vegetation changes during the Mazovian Interglacial and the older part of Liviecian Glaciation in the western and central parts of Polish Uplands (Figs 1—6). The investigation has been based on results of pollen analysis (Tab. 8—12, Figs 7—18) and examination of macroscopic remains of plants (Tab. 15—21, Figs 28—36) from six sites (Konieczki, Raków, Malice, Wielki Bór, Katowice and Białe Ługi) as well as additional results from archival sites prepared by other authors. Pollen successions in new sites represent all basic features, which were characteristic for the succession of the Mazovian Interglacial, the typical order of pollen culmination of particular trees, occurrence of yew (Taxus), interglacial increase in pine (Pinus sylvestris t.) values, coexistence of high values of hornbeam (Carpinus) and fir (Abies) pollen in the younger part of the interglacial period and occurrence of marker taxa, such as Pterocarya, Celtis and Azolla filiculoides. There have not been found any sediments representing the end of the San Glaciation 2, preceding the Mazovian Interglacial. The forest landscape in the oldest part of the interglacial was homogenous, without any significant regional variation. A high proportion of Betula alba t. pollen, in some samples reaching even 93% (Fig. 19), proves there were almost only birch forests then. Changes in the forest landscape were caused by expansion of pine (Pinus sylvestris t.) and later of spruce (Picea abies) and alder (Alnus). Further expansion of yew (Taxus) caused great changes in the upland forest landscapes, which were dominated by yew communities (maximum pollen proportion 62% in Konieczki, 53% in Malice, 52% in Raków and 46% in Wielki Bór, Figs 20, 21, 37). Later, the upland area became dominated by pine and birch communities, which was the result of cool climatic oscillation. Increase of importance of hornbeam and fir initiated further changes in the forest communities. At the end of the interglacial, importance of pine increased again and thermophilous trees retreated from the upland areas (Figs 24, 25). Changes of vegetation, which occurred due to climate worsening, have been recorded in sediments from all the sites. The succession of pollen was the most complete in the older part of the Liviecian Glaciation in the Wielki Bór profile (WB1 and WB2), where three cold and two warm oscillations of the climate, as stadial and interstadial, have been registered and in Raków (R1) site, two stadial and two interstadial ones have been found. The other sites (Konieczki, Malice 3, Katowice 1 and Białe Ługi 1, 2, 3 and 4 profiles) represent the fragment of the I stadial only (Figs 26, 27). Organic sediments in the older part of the Mazovian Interglacial are most frequently represented by alternative strata of silt and gyttja (Tab. 1—5) and they do not contain macroscopic plant remains. The remains appeared in larger amount starting from the III period sediments (Wielki Bór 1, Konieczki and Katowice 1) or the IV pollen period (Malice 3). Contents of the macroscopic plant remains, variety of green algae of the Pediastrum genus, and spore-pollen data emphasise significant changes of trophism in several lakes. Occurrence of Isoëtes lacustris spores (micro- and macrospores) in sediments in Białe Ługi (Fig. 35) proves oligotrophic conditions, which existed in the lake in the oldest and the youngest part of the Mazovian Interglacial and the oldest part of the Liviecian Glaciation. Occurrence of Isoëtes rugosa (micro- and macrospores) in sediments in Wielki Bór (Fig. 31) can be also correlated with the glaciation. Appearance of Aracites interglacialis seeds, the species characteristic for the interglacial, which has been determined in the sediments in Białe Ługi, seems to be quite significant. Similar course of pollen curves of the main taxa in the profiles of the upland areas have enabled to correlate most of the local pollen zones (L PAZ) with the regional pollen zones (R PAZ) after KRUPIŃSKI (1995 a, 2000) (Tab. 22). Pollen successions from the uplands have been compared with the successions from the Podlasie region, as it is the only area in Poland with a large number of sites of modern palynological studies and a dense net of profile sampling. Increase in the val-ues of Betula and Pinus pollen in the younger part of Alnus-Pices-Fraxinus zone (II pollen period, Fig. 20), is a local feature characteristic for the pollen successions in the sites in the Woźniki-Wieluń Upland (Konieczki, Raków, Malice and Wielki Bór). It was probably caused by drying of some of the habitats due to hydrological changes. Very high proportion of Carpinus pollen (39% and 49%), observed in Białe Ługi (BŁ1 and BŁ4) and Zakrucze profiles (Fig. 23), not recorded in any other sites of the Mazovian Interglacial, is an unexpected feature. Expansion of the tree probably occurred in the same time as the increase of pine importance in the Woźniki-Wieluń Upland (Pinus-Picea-Carpinus or Pinus-Carpinus zone, Fig. 22), which occurred in the beginning of the interglacial climatic oscillation, resulting from stronger influence of the continental climate. Climatic and vegetation changes during the interglacial climatic oscillation were probably stronger than it has been assumed so far. The period of the most substantial changes can be correlated with the Betula-Pinus zone, which has been determined so far only in Ossówka (KRUPIŃSKI, 1995 a), Woskrzenice (BIŃKA, NITYCHORUK, 1995) and Konieczki (NITA, 1996, 1999). Increase in the values of Betula and Pinus pollen and concurrent, quite drastic decrease in the pollen proportion of thermophilous trees of Betula-Pinus zone in Raków and Białe Ługi profiles (Fig. 36), proves that similar changes in the profiles from Konieczki and Podlasie region were not incidental and did not have a local character. Birch and pine forests expanded in most of the area of Poland and thermophilous trees almost completely retreated in that time. Only spruce (Picea abies) and alder (Alnus) among the trees, which had been previously dominating, remained in the forest landscape. Climatic optimum of the Mazovian Interglacial was a relatively long time period. Warm and humid climate already lasted during the expansion of yew (Taxus-Alnus zone) and later during the development of communities with hornbeam and fir (III pollen period according to JANCZYK-KOPIKOWA, 1991). Quite possibly, the contemporary average temperatures of July were slightly higher than during the yew zone, however the period was not stable as far as the climate was concerned. It is possible to agree with KRUPIŃSKI (1995 a, 2000), that the climatic optimum covered a relatively long time period from the expansion of yew till the development of communities with hornbeam and fir. Modern climates in the western part of Polish Uplands and Podlasie region vary much more significantly than in the Mazovian Interglacial. Influence of the oceanic climate reached further to the east than today. Differences in the pollen successions in both of the areas have been caused mainly by local factors such as: soils, hydrological conditions or microclimates. Low and very low pollen proportion of Carpinus and very high values of Abies, found in the younger part of the III pollen periods in the upland profiles (Figs 22, 23) might prove slightly longer influence of the oceanic climate than in the Podlasie region. However, even in that case influence of local factors cannot be omitted. Fir (Abies alba), as a „mountain” species, could have found more favouring expansion conditions in the upland.