Detection of the impact of early Holocene hunter-gatherers on vegetation in the Czech Republic, using multivariate analysis of pollen data (original) (raw)

2007, Vegetation History and Archaeobotany

This thesis took a long way to finish, and this would not be achieved without all scientific and mental support of all my colleagues, friends and family. First, I would like to thank to my supervisor Petr Pokorný for encouraging me to start with a very interesting but very incalculable topic, for keeping supporting me quite a long time, for fruitful discussions not only about palaeoeology and for friendship. Studying the Mesolithic would not be possible without cooperation with archaeologists. The one who had great influence is Petr Šída. I appreciate we could start cooperation on environmental topics concerning the hunter-gatherer populations. Another person I would like to thank is Dagmar Dreslerová, who supported me with fruitful discussions upon archaeological and palaeoclimatological topics, and who encouraged me when I was down. Another part of my work, which I really appreciate, is that I could join the team of Milan Chytrý working in southern Siberia. Milan is acknowledged for giving me great ideas, supporting me on expedition and for a great help during writing manuscripts. Barbora Luèenièová is thanked for cooperation during pollen determination and preparation of manuscripts. I am grateful to numerous members of Siberian vegetation-survey team. I thank to Vlasta Jankovská for general support and for providing her data. I am grateful to Marie Peichlová, Libor Petr, Petr Pokorný, Eliška Rybníèková and Helena Svobodová-Svitavská who also kindly provided data. During my Ph.D. studies I visited several times the group of palaeoecology at the IPS, University of Bern. I really appreciate a continuous support which gave Brigitta Ammann not only to me, but for the whole Czech palaeoecology. I also greatly thank to Jacqueline van Leeuwen and Pim van der Knaap for teaching me in the fields of palynology and palaeoecology, for many excursions we made (even the research trip to Galapagos) and for their friendship. I thank to Agnieszka Wacnik, Jacek Madeja and Ewa Wypasek all from Krakow for exchanging ideas, fruitful meetings and for making wonderful excursions, especially to the Great Masurian Lakes District. I am extremely grateful to my fellow colleagues Vojtìch Abraham, Radka Kozáková, Libor Petr for making a great atmosphere of inspiration. I also thank to Miloš Kaplan † who, hopefully, finally found peace. I acknowledge Tomáš Herben for continuous support for palaeoecology at the department and for encouraging me to start with it. I thank to Jan Zápotocký for giving me help with finalization and pre-print procedures of the manuscript. The research would not be possible without financial support of different projects. I was supported by long-term project of the Ministry of Education no. MSM0021620828, then by grants of the Grant Agency of the Academy of Sciences no. KJB6111305 and IAAX00020701. Parts of the research were financed under Ministry of Environment (project SE/620/7/03) and Grant Agency of the Academy of Sciences (project IAA6163303). Tímto bych chtìl podìkovat svým rodièùm, kteøí mì podporovali po celou dobu mého studia, aè jim musela pøipadat neúmìrnì dlouhá. Chronologically, the period of interest starts with the oxygen isotopic stage 2 (OIS 2; 30 ka B.P., according to Bond et al., 1997) and ends after the last cooling event 8200 cal. B.P. with the beginning of the Holocene climatic optimum. Culturally, this is the period of late Palaeolithic and Mesolithic hunter-gatherers, who finally vanished with oncoming neolitisation (Fig. 1). The late Pleistocene period, which had a huge significance for humans (Finlayson & Carrion, 2007), was traditionally depicted as harsh glacial maximum climate. But this, paradoxically, apply to a small fraction around 18 ka B.P. (21-21.5 ka cal. B.P.) only. Glacial climate before the last glacial maximum (LGM) and late-glacial climate after it was far less severe (van Andel & Tzedakis, 1996). The question remains how responded the vegetation to these changes. Modelling vegetation patterns during the glacial period is an issue since Frenzel (1968) proposed his concept. Even he suggests some forest vegetation in central-eastern Europe in the LGM. Recent simulations for the Interpleniglacial (OIS 3) place taiga vegetation to central Europe (Huntley et al., 2003). Even models for vegetation distribution in the LGM show boreal-forest or forest-tundra (Harrison & Prentice, 2003), however, pollen data from central Europe were missing for calibration of these models. Studying vegetation and climate changes has possible implications for understanding patterns of migration of human population during the OIS 2 as their adaptive responses (Svoboda, 2007). The afforestation process started due to warming and relatively stable climate at the beginning of the Holocene. New set of species immigrated and established climax broadleaf forests. The afforestation in central Europe was probably at the highest level that time. However, there are different views whether it was complete or there still existed a lot of open spaces (see Lo ek, 2004; Sádlo et al., 2005; Vera, 2000). This is especially important considering this period as the time of last hunter-gatherers. Human populations started to be less mobile and probably affected local environments more intensively. Although ecosystems are still considered as naturally evolved, humans could play very significant role in supporting survival of some steppic species in generally forested landscape. They also could act supporting intentional or unintentional migration of some species. On the other hand, humans probably contributed to final extinction of megafauna in central Europe, namely mammoth, rhinoceros or European bison (Burney & Flannery, 2005; Wroe et al., 2006). All of them were big herbivores and their dismissing could play very important role in vegetation development. Since, it is very difficult to find any significant traces of hunter-gatherers in central-European ecosystems by mean of palaeoecological methods, we find very useful, and this is a specific aim of the present thesis, to search for traces of human impact. Reconstruction and interpretation of various stages of glacial and early postglacial vegetation, climatically induced development of no-analog communities and evolution of human impact, which finally led to evolution of cultural landscape, are very important questions in palaeoecology. Vegetation during of the last glacial and early Holocene in central Europe Traditional views depicted vegetation development in central Europe since the pleniglacial to the Holocene as a final dominance of forest over treeless steppe or tundra vegetation. Cold glacial period was determined as treeless landscape, while warming up forced immigration of trees from the south at the end of the glacial. However, recently we have more sophisticated information about the glacial climate, which led to numerous suggestions and models, that central European landscape and vegetation did not suffer that much from such severe conditions during the whole glacial. Most recent views about the last glacial and early postglacial vegetation in central Europe are briefly described below. Vegetation and climate during the OIS 3 (Fig. 1) was widely studied by the OIS Three Project (Cambridge, 2003). It suggested that during the warmer interstadial phases central Europe could harbour parkland vegetation with coniferous trees, even with some admixture of broadleaf trees. These models were so far hardly supported by very few palaeobotanical data. Some records come from Western Europe and southern Poland. Palaeobotanical finds from Moravia and Hungary are discussed in Chapter 3. What we find crucial is correct interpretation of these finds. Even during the coldest stages of the pleniglacial there could still exist isolated populations of tree species in periglacial landscape (Lang, 1994). Their habitats could be most probably situated along rivers (already proposed by Frenzel (1968)) or in protected intermontane valleys (see Chapter 3). This also supports new theories about no-existent/discontinuous permafrost during warm/cold stages of the pleniglacial (Alfano et al., 2003). Although we have only modelled data for the LGM in central Europe, there exist records from southern and eastern Europe interpreting vegetation as glacial steppe (Elenga et al., 2000; Tarasov et al., 2000). Question is whether trees survived the LGM in central Europe? One positive answer can bring comparison of climate, which did not differ that much between warm and cold periods, and BIOME model of vegetation during the LGM (Harrison & Prentice, 2003). Another answer can bring new palaeobotanical finds presented in Chapter 3, showing that trees massively occurred in early late-glacial pollen records. Generally we may assume that climate during the OIS 3 and 2 most probably had large local or regional discrepancies, which influenced vegetation distribution and possible existence of local refugia. During the last interstadials in late Pleistocene, taiga vegetation developed. It retreated during cool stadial phases and spread again at the beginning of the Holocene. This is well documented by several pollen assemblages in central and central-eastern Europe (see (Williams & Jackson, 2007), compositionally unlike of any found today, and with no-analog climate conditions (lowered CO2, seasonality insulation or persistent ice-sheet). These assumptions can also influence possible convergence or divergence in relationship between vegetation and assemblages. Errors can arise from such sources in analog analysis. Scheme and main questions of the work Chapter 1 brings the general assumptions and introduction to the problem, which is being resolved in particular studies. They are sorted in this work chronologically. Chapter 2 'The relationship of modern pollen spectra, vegetation and climate along a steppe-forest-tundra transition in the Western Sayan Mts., southern Siberia, explored by decision...