Antropogénni vliv na změny krajiny a vegetace odrážející se v pylových spektrech ze středovýchodní Evropy.

Prezentovaná práce je zaměřena na vliv lidských společenství na změny vegetace a transformace krajiny v regionu střední Evropy. Hlavním cílem studie bylo zhodnotit, jak se minulé lidské činnosti odráží v pylových spektrech z různých typů a většinou malých lokalit. Člověk svou činností přispěl ke vzniku a šíření různých typů otevřených stanovišť, změnil složení vegetace introdukováním nových druhů, ovlivnil strukturu a složení lesů a podpořil zrychlení geomorfologických procesů, jako je eroze půdy a akumulace sedimentů. Změny ve složení vegetace vyvolané činností člověka se odráží v pylových spektrech. Za přímý důkaz lidské činnosti v pylových spektrech je považována přítomnost pylových zrn pěstovaných rostlin. Existuje také několik nepřímých stop indikujících lidský vliv na krajinu, jako je šíření sekundárních antropogenních indikátorů (apofyty), fluktuace v pylových křivkách dřevin jako důsledek změn v pokryvu krajiny nebo složení lesa, zvýšením množství mikro-uhlíků v důsledku lidmi založených požáru nebo erozní procesy způsobené lidskou aktivitou. V kapitole 1 se potvrdil předpoklad, že dopad neolitické lidské činnosti v krajině je v pylových spektrech téměř neviditelný, nicméně, několik nepřímých stop indikují přítomnost lidských komunit v těsné blízkosti místa studie. V kapitole 2 a 4 je...The present thesis focuses on the impact of human communities on postglacial vegetation changes and landscape transformation in the region of Central-Eastern Europe. The main aim of the study was to evaluate how past human activities are reflected in pollen spectra from different types of mostly small-sized sites. Since the Middle Holocene onwards, human impact contributed to the formation and spread of various types of open habitats, altered the vegetation composition by introducing new species, influenced forest structure and supported the acceleration of geomorphic processes such as soil erosion or sediment accumulation. Human-induced alteration of the landscape cover and vegetation composition is reflected in pollen spectra, but it is often difficult to identify. Considered as direct evidence of human activities are the presence of pollen grains of cultivated plants in pollen spectra. Besides, there are several indirect traces of human impact on the landscape such as the spread of secondary anthropogenic indicators (apophytes), fluctuation in pollen curves of trees as a consequence of change in landscape cover or woodland composition, increases of micro-charcoal particles due to human-induced fire or erosion processes. Chapter 1 presents confirmation of the assumption that Neolithic human...Department of BotanyKatedra botanikyFaculty of SciencePřírodovědecká fakult

Fire hazard modulation by long-term dynamics in land cover and dominant forest type in eastern and central Europe

Wildfire occurrence is influenced by climate, vegetation and human activities. A key challenge for understanding the risk of fires is quantifying the mediating effect of vegetation on fire regimes. Here, we explore the relative importance of Holocene land cover, land use, dominant functional forest type, and climate dynamics on biomass burning in temperate and boreo-nemoral regions of central and eastern Europe over the past 12 kyr. We used an extensive data set of Holocene pollen and sedimentary charcoal records, in combination with climate simulations and statistical modelling. Biomass burning was highest during the early Holocene and lowest during the mid-Holocene in all three ecoregions (Atlantic, continental and boreo-nemoral) but was more spatially variable over the past 3–4 kyr. Although climate explained a significant variance in biomass burning during the early Holocene, tree cover was consistently the highest predictor of past biomass burning over the past 8 kyr. In temperate forests, biomass burning was high at ~ 45% tree cover and decreased to a minimum at between 60% and 70% tree cover. In needleleaf-dominated forests, biomass burning was highest at ~60 %–65%tree cover and steeply declined at > 65% tree cover. Biomass burning also increased when arable lands and grasslands reached ~15 %–20 %, although this relationship was variable depending on land use practice via ignition sources, fuel type and quantities. Higher tree cover reduced the amount of solar radiation reaching the forest floor and could provide moister, more wind-protected microclimates underneath canopies, thereby decreasing fuel flammability. Tree cover at which biomass burning increased appears to be driven by warmer and drier summer conditions during the early Holocene and by increasing human influence on land cover during the late Holocene. We suggest that longterm fire hazard may be effectively reduced through land cover management, given that land cover has controlled fire regimes under the dynamic climates of the Holocene

The Reading Palaeofire Database : an expanded global resource to document changes in fire regimes from sedimentary charcoal records

Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using IntCal20 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1676 records (entities) from 1480 sites worldwide. The database (RPDv1b - Harrison et al., 2021) is available at https://doi.org/10.17864/1947.000345.Peer reviewe

Anthropogenic impact on landscape transformation and vegetation changes reflected in pollen spectra from Central-Eastern Europe.

The present thesis focuses on the impact of human communities on postglacial vegetation changes and landscape transformation in the region of Central-Eastern Europe. The main aim of the study was to evaluate how past human activities are reflected in pollen spectra from different types of mostly small-sized sites. Since the Middle Holocene onwards, human impact contributed to the formation and spread of various types of open habitats, altered the vegetation composition by introducing new species, influenced forest structure and supported the acceleration of geomorphic processes such as soil erosion or sediment accumulation. Human-induced alteration of the landscape cover and vegetation composition is reflected in pollen spectra, but it is often difficult to identify. Considered as direct evidence of human activities are the presence of pollen grains of cultivated plants in pollen spectra. Besides, there are several indirect traces of human impact on the landscape such as the spread of secondary anthropogenic indicators (apophytes), fluctuation in pollen curves of trees as a consequence of change in landscape cover or woodland composition, increases of micro-charcoal particles due to human-induced fire or erosion processes. Chapter 1 presents confirmation of the assumption that Neolithic human..

Abrupt vegetation and environmental change since the MIS 2: A unique paleorecord from Slovakia (Central Europe)

Research on past abrupt climate change and linked biotic response is essential for understanding of the future development of biota under changing climatic conditions, which, in turn, is necessary for adequate progress in ecosystem management and nature conservation. The present study presents the first comprehensive reconstruction of local and regional environment at the Western Carpathian/Pannonian Basin border, including a first chironomid-based paleoclimate reconstruction and d18O and d13C records from travertine, to investigate abrupt biota and climate shifts since the Marine Isotope Stage (MIS) 2. A range of biotic and abiotic proxy data in organic-calcareous sediment sequence were analysed using a multi-proxy approach to produce a detailed reconstruction of past ecosystem conditions. The results illustrate that the most prominent abrupt change in the local environment occurred directly at the MIS 2/ MIS 1 transition at 14,560 cal BP as a consequence of increased precipitation and an increase in reconstructed mean July temperature by ~2.2 C. Abrupt changes in local environment during the early Holocene were closely linked to travertine precipitation rate around thermal springs and thus indirectly to the climate until the arrival of the Late Neolithics around 6400 cal BP. Regional vegetation response (derived from pollen data) to the climatic fluctuations lagged, with the most prominent changes around 14,410 cal BP and 10,140 cal BP. Our data suggest the presence of a steppe-tundra ecosystem with evidence for low amounts of temperate broadleaf trees during the MIS 2, indicating close proximity to their northern glacial refugium. We demonstrate the ability of d18O and d13C stable isotope record from travertine to reflect abrupt climatic and environmental changes. The study provides evidence about benefits using travertine deposits coupled with high-resolution paleoecological data to investigate past biotic and abiotic responses to abrupt climate change

Pollen counts

Pollen counts extracted from the Czech Quaternary Palynological Database (https://botany.natur.cuni.cz/palycz/) on 2 November 2017 covering the entire study area. Pollen taxonomy follows Beug (2004). Age is given in the calibrated age scale in BP (0 cal BP = 1950). Regions are defined as in Kuneš et al. (2009)