107 Ferrantia • 44 / 2005 P. Pokorný & P. Kuneš Holocene acidification process recorded in pollen profiles, Czech Republic Holocene acidification process recorded in three pollen profiles from Czech sandstone and river terrace environments Petr POKORNÝ Institute of Archaeology, Academy of Sciences of the Czech Republic Letenská 4, CZ-118 01 Praha 1 pokorny@arup.cas.cz Petr KUNEŠ Department of Botany, Charles University in Prague Benátská 2, CZ-128 01 Praha 2 cuneus@natur.cuni.cz Introduction Late Quaternary climatic changes had dramatic effect on the terrestrial biosphere. In temperate mid-latitude regions of the Northern Hemisphere, vegetation belts migrated over several thousands of kilometers. These macroscale vegetational changes were accompanied (and were partly in response to) changes in soil properties. The ways in which soil-vegetation relationships have evolved, and particularly the response of vegetational and pedogenetic processes to climatic change, are of fundamental importance in understanding the dynamics of contemporary ecosystems. Viewed in this light, acidification is a long-term natural process that occurs especially during warm phases of Quaternary climatic cycle (Iversen 1958; Birks 1986). It is characterized by loss of cations (namely bivalent bases - Ca 2+ and Mg 2+ ) that are normally bound to clay minerals in the soils. Under wet and warm conditions, bases are leached from these complexes, being dissolved in percolating water and transported out of the ecosystem (and finally through the rivers to the sea). This process results in change in species composition and produc- tivity of the ecosystems. The dynamics of acidifi- cation is seriously modified by climatic changes, biotic influences, and, during the Holocene, also by human intervention (Bell & Walker 1992). Antropogenic activities contribute to the acidi- fication through removal of biomass (grazing, mowing, woodcu�ing, harvesting without subse- quent manuring) and through triggering the soil erosion. Positive backbound mechanisms may play an important role in case of biological control of acidification. To give a simple example from Central Europe: At the first stage of acidification, coniferous trees (namely Pinus sylvestris, Picea abies, and Abies alba) spread within broadleaf forests. During the decomposition of coniferous falloff, humic acids are produced in great quantities. Organic compounds in soils change from mull to mor humus. This efficiently speeds up further acidification and soils structure is changed in the process called podzolisation. Usually also upper layer of underlying bedrock is being leached and decalcified. Due to its long long-term nature, acidification processes can be best studied in secular to millennial time scale. Pollen analysis is appro- priate tool for this as it enables to record time scales long enough and because vegetation corre- sponds directly to local geochemical changes. The pollen and sediment chemistry evidence Soils developed on relatively acidic bedrock are o�en more sensitive to loss of nutrients than those on calcareous substrata. This is why best evidence for Holocene acidification in the Czech Republic comes from sandstone regions and from river environment with extensive cover of acidic sands and gravel. In the following, we will give three examples of profiles, where acidification process can be studied (location of profiles indicated in Fig. 1). Anenské údolí, Broumovsko sandstone region The site, a topogenic mire in the bo�om of a valley at 645 m a.s.l. altitude, is surrounded by dramatic