ИСТИНА

Paleosols are a fundamental source of evidence for environmental processes that took place in the past, and, as such, they may also be used in models that aim on predicting future earth system reactions to changing environmental conditions. Thus, large numbers of papers on paleopedology are continuously being published, summing up to at least 142 papers in 2006, 152 in 2007, and 141 in 2008, if only the international journals listed in Scopus are considered. Many more papers have been presented on the web: 1510 papers in 2006, 1410 in 2007, and 1290 in 2008 (Google). Most contributions to this special issue of Quaternary International were presented in the paleopedology sessions held during the INQUA congress in Cairns, Australia, 28th July–3rd August 2007. They reflect several recent foci of paleopedological research, which may be grouped as follows: 1. Use of soil characteristics as palaeo-climatic proxies 2. Rates of pedogenic processes 3. Periglacial sediments, loess and dust 4. Use of pedogenic carbonates as palaeo-archives in interdisciplinary studies, including impacts of environmental changes on man 5. Concepts in paleopedology 6. Heritage soil documentation and protection 1. Use of soil characteristics as palaeo-climatic proxies A central aim of paleopedology is reconstructing palaeo-climate from paleosols. The first two papers of this volume (Pal et al.; Hu et al.) deal with the suitability of some chemical, micromorphological and magnetic soil characteristics for palaeo-climatic interpretation. Pal et al. present a Vertisol climosequence in India, which includes six pedons in a climatic range from warm humid (MAP: 3287 mm) to warm dry (MAP: 533 mm) conditions. Following the actualistic principle, the authors identify specific macro- and micromorphological features and chemical properties in the Vertisols, which they relate to different present climatic conditions in the different study areas. These climate-related soil properties are then used to reconstruct a Holocene transition from more humid to drier conditions. The paper of Pal et al. contributes to the important issue of determining the climatic ranges in which certain pedogenic features may occur in order to draw proper conclusions from these features when they occur in paleosols. Hu et al. try to link the magnetic susceptibility of Tertiary Red Clay (TRC) on the Chinese Loess Plateau to pedogenic processes. Magnetic susceptibility variations in Quaternary loess–paleosol sequences in the Chinese Loess Plateau are commonly used to reconstruct Quaternary palaeo-climatic cycles ( Liu, 1985 and An et al., 1991), whereby increased susceptibility is generally attributed to the formation of pedogenic superparamagnetic grains during soil development ( Zhou et al., 1990, Maher and Thompson, 1991 and Verosub et al., 1993). In recent years, attempts have been made to extend the magnetic record to the TRC that underlies the loess ( Ding et al., 1998, Ding et al., 1999, Sun et al., 1998a, Sun et al., 1998b, Guo et al., 2002, Liu et al., 2003 and Hao and Guo, 2007). Hu et al. report that the TRC of the Lingtai section in the Chinese Loess Plateau is generally more intensively weathered than the Quaternary paleosols in the overlying loess. However, magnetic susceptibility of the TRC is significantly lower than that of the Quaternary paleosols. The authors conclude that magnetic susceptibility cannot be used as a palaeo-climatic proxy in the TRC. They interpret lower contents of ferrimagnetic minerals and higher hematite and/or goethite contents in the TRC as a result of the transformation of ferrimagnetic minerals into hematite. Although the specific processes that lead to low magnetic susceptibility in the highly weathered TRC could not completely be identified, the paper points to a very important issue, i.e. the need to understand the processes behind magnetic susceptibility when using this parameter as a palaeo-climate proxy. 2. Rates of pedogenic processes Rates of pedogenic processes are commonly studied in soil chronosequences, which are usually established on sequences of river terraces (e.g. Torrent, 1976, Arduino et al., 1984, Arduino et al., 1986, Ajmone Marsan et al., 1988, Bain et al., 1993, Engel et al., 1996, Leigh, 1996, Vidic and Lobnik, 1997, Shaw et al., 2003 and Tsai et al., 2006), marine terraces (e.g. Muhs, 1982, Aniku and Singer, 1990, Markewich and Pavich, 1991 and Merrits et al., 1991Moody and Graham, 1995, Scarciglia et al., 2006, Tsai et al., 2007 and Wagner et al., 2007), beach ridges (e.g. Protz et al., 1984, Protz et al., 1988, Nieuwenhhuyse et al., 1993, Nieuwenhhuyse et al., 1994 and Sauer et al., 2007), moraines (e.g. Alexander and Burt, 1996, Evans, 1999, Righi et al., 1999 and Egli et al., 2001), or dunes of different ages (e.g. VandenBygaart and Protz, 1995, Lichter, 1998 and Stützer, 1998). Numerous soil chronosequence studies have been carried out in the last decades, particularly on the formation of Podzols (e.g. Barrett, 2001, Tonkin and Basher, 2001, Mokma et al., 2004 and Sauer et al., 2008) and Mediterranean soils (e.g. McFadden and Hendricks, 1985, Busacca, 1987, Diaz and Torrent, 1989, Alonso et al., 1994, Dorronsoro, 1994, Bech et al., 1997, Garcia Marcos and Santos Frances, 1997 and Costantini et al., 2002). Sauer et al. present in this volume the first chronosequence of Albeluvisol formation, which has been established on Holocene loamy marine sediments in the humid-temperate climate of southern Norway. Preliminary results of the study have been published by Schülli et al. (2007). The authors report that in this area, clay illuviation starts in less than 1650 years. E horizons become lighter with age, but their lower boundary stays around 40 cm for more than 10,000 years. Albeluvic tongues start to develop between 4600 and 6200 years. Fed/Fet ratios of the soils show a clear linear increase with soil age. The following paper of Zielhofer et al. presents rates of soil formation in a Holocene Mediterranean floodplain. The authors previously reported palaeo-environmental reconstructions for the area, based on paleosol–sediment sequences of floodplains ( Zielhofer et al., 2002, Zielhofer et al., 2004, Zielhofer et al., 2008, Faust et al., 2004 and Zielhofer and Faust, 2008). Their new paper focuses on the quantification of soil development stages in this type of palaeo-archive. In particular, the authors demonstrate that the profile development index, introduced by Harden (1982) and Harden and Taylor (1983), modified by Birkeland (1999), correlates well (R2 = 0.8) with the independently determined duration of soil formation periods. The overall aim of this approach is to make use of this correlation for estimating the duration of soil formation periods from profile development indices in cases, where no other chronological control is provided. Knowledge on the duration of soil formation periods is an important issue in the interpretation of alluvial archives, because they indicate periods of decreased flooding and low sedimentation rates (Zielhofer et al., 2002). 3. Periglacial sediments, loess and dust It is well known that paleosols on loess and other dust sediments are among the most favourable objects in paleopedological research, because mobilization and sedimentation of dust are strongly controlled by climatic factors and are often interrupted by periods of stability and soil formation. Four papers of this volume are related to loess–soil interaction in various regions: Terhorst et al. (Austria), Makeev (Russia), Cattle et al. (Australia) and Costantini et al. (Italy). In spite of the fact that studied soils are widely spread geographically and chronologically, the papers have much in common, as they focus on surface and near surface loess and/or periglacial sediments, influenced by pedogenesis and morphodynamic processes. The following issues arise from the nature of the materials: 1. Identification of loess sediments is usually an important part of research, because they could be considerably altered by pedogenesis, periglacial processes and/or mixed with underlying or cover sediments by slope processes and bioturbation; 2. The sources of dust material could be local, distal, or mixed; 3. Dating of loess and related sediments is required; 4. Reconstruction of initial dust sediment features and thus the rate, degree and stages of their transformation by pedogenesis and slope processes is needed; 5. The role of sediment and pedogenic features in slope stability, must be assessed; and, based on this, 6. Forecasts of landscape stability in present environments and in the case of future climate changes can be attempted. The study of soil and loess features is an essential part of research in the paper of Terhorst et al., revealing slope evolution in conjunction with other geomorphic parameters, where phases of erosion, redeposition, sedimentation, and soil formation demonstrate stages of activity and stability under varying climatic conditions. Pleistocene and Holocene sediments and processes are differentiated, based on the concept of periglacial cover beds. Distribution of periglacial cover beds, loess and modern soils allows reconstruction of the original Pleistocene slope and sediments. Soil features, critical for assessment of slope movement, such as soil mechanical stability criteria or signs of waterlogging, are discussed and form the base for predicting slope movements in the study area, especially with regard to intensive human activities. There was no problem of loess identification in the paper of Makeev, because the area belongs to the Northern fringe of East European loess belt with thick loess strata. The paper focuses on reconstructing stages of final loess sedimentation during the Late Pleistocene, partly within profiles of surface soils. Sequential sedimentation is not obvious in the homogeneous loess strata on the main surfaces, but becomes clear in corresponding loess layers within paleocryogenic depressions, where dust accumulation was accompanied by slope and cryogenic processes and hydromorphic pedogenesis. Comparing loess sediments within and outside of depressions confirmed pedogenic alteration of primary dust sediments on the main surfaces under cold arid environments that left no developed soil profiles. Transformation of loess within depressions caused considerable degradation of initial features (leaching of carbonates, partial loss of structure, hydromorphic features). The paper of Cattle et al. describes loess-derived (parna) soils in south-eastern Australia, where red clayey calcareous dust material was deeply transformed in the course of 10,000–50,000 years of pedogenesis. To confirm the aeolian nature of sediments, the authors provide a model of aeolian mobilization and depositional cycles. To determine the pedogenic impact of initial windblown sediments and to link variable loessic soil features with initial windblown sediments, the authors demonstrate a broad climosequence along the “wind tube”, the main dust transport route, with annual precipitation ranging from 443 to 654 mm and elevation ranging from 125 to 635 m a.s.l. Research is supplemented by the study of two soil profiles within soil catena to demonstrate the impact of local landscape processes on loessic soil features. Special attention is given to the role of sediment and pedogenic features in landscape stability, on the bases of morphological, physico-chemical and structural stability attributes. Well-drained soils will have little impact on landscape instability, whereas in the lower landscape positions degradation of loessic features in the course of pedogenesis leads to transformation of structure, salinisation and/or sodification, increasing the risk of erosion. Recognition of Holocene loess sediments, never mentioned before in central Italy, is the main focus of the paper of Costantini et al. The problem of loess identification is explained by its spatial distribution, small thickness (sometimes only an admixture of separate aeolian grains), admixture of underlying sediments and alteration by pedogenesis. Application of a set of morphological (including light and electron microscopy), mineralogical, and geochemical methods, supplemented by pollen analyses and age estimation, allowed thorough characterization of loess horizons in polycyclic profiles of the Elsa basin. Comparing the features of loess with that of local sediments helped to exclude distant sources and confirmed that the prevalent source of dust was local, with dust particles bearing signs of both aeolian and hydrodynamic transport. The stages of increased colluviation were established in older deposits and correlated with the Heinrich events. The study of loess soil features and pollen spectrum allowed Costantini et al. to recognize aridization, caused both by climatic change and increased human activity in the mid-Holocene. Increased arid conditions in the course of climate change could trigger a new cycle of slope denudation, wind erosion and loess deposition. 4. Use of pedogenic carbonates as palaeo-archives in interdisciplinary studies, including impacts of environmental changes on humans Another issue of interdisciplinary studies in the last decades is related to environmental changes during the Holocene, particularly those having consequences on the history of humanity. A major aim of these studies is improving the understanding of relationships between climatic changes, environmental processes and human adaptation and reaction. Links between soil processes and the development and collapse of civilizations, as well as migration of populations, have been known for a long time. These issues are of utmost relevance today, as pressure of man on the natural resources, in particular water, soil, and vegetation, increases. However, there are still many uncertainties with regard to the resilience capacities of both, natural resources and human communities operating on them (Blum et al., 2006). Moreover, earth system feedbacks to climatic variations can be non-linear, but determined by thresholds. Crossing such thresholds may lead to abrupt non-linear changes, even if the causative climatic transitions are not abrupt. The work of Riehl et al. presented in this volume deals with consequences of Holocene climatic changes on agriculture and human occupation in the Fertile Crescent in the Near East. The authors test the reconstruction of environmental changes obtained from pedogenic carbonate coatings on stones with other palaeo-environmental archives: i) plant macroremains from archaeological sites, ii) stable carbon isotope composition of plant macroremains, and iii) modelled Holocene precipitation and temperature changes. Pedogenic carbonates are valuable indicators of palaeo-climate and -environment. Their formation is part of the soil development in semi-arid to sub-humid climates, and their isotopic composition reflects the environmental conditions during the formation of the paleosols in which they occur. Carbon isotope ratios in pedogenic carbonates are governed primarily by that of soil CO2, oxygen isotopes by that of atmospheric precipitation. Pustovoytov et al. (2007) used pedogenic carbonate coatings on stones to reconstruct late Quaternary environmental changes in northern Mesopotamia. A similar approach enabled Bettis et al. (2009) to document the environmental conditions at the time when Homo erectus spread through Southeast Asia during the early Pleistocene. Kovda et al. (2009) found that carbonate morphologies and distribution in paleosols of Russia reflect wet–dry and cold–warm cycles. They observed several generations and multiphase formation of carbonate pedofeatures in a loess–paleosol pedocomplex. Pedogenic carbonates have been extensively used as environmental and dating proxy in a number of other recent works on Holocene paleosols ( Khokhlova et al., 2001 and Frank et al., 2006), as well as Plio–Pleistocene (Levin et al., 2004), up to Permian and Triassic paleosols (Tabor et al., 2004), which demonstrates the potential of pedogenic carbonates as palaeo-archives. Further development may include the development of quantitative models of pedogenic carbonate formation under different environmental conditions. 5. Concepts in paleopedology The paper of Iriondo presented in this volume introduces a “Multisol” concept, to advance a three-dimensional approach in studies of paleosols and associated sediments. A Multisol is defined as a soil body that, maintaining an identifiable continuity, bifurcates in two or more layers located at different levels of the sedimentary column, and connotes a sedimentary body. The general issue of studying paleosols as part of three-dimensional landscapes has received interest for several decades. In the “Conclusions of the working group on the origin and nature of paleosols”, adopted in Amsterdam in 1970, it was stated that “both partial and complete profiles should be traced laterally in the landscape to determine their spatial variation” (Yaalon, 1971). Linking stratigraphic, geomorphic, and pedological observations has been a main element of the methodological approach of many paleopedological studies (e.g. Blecker et al., 1997, Retallack, 1998, Scarciglia et al., 2005, Jacobs and Mason, 2007 and Terhorst, 2007). New possibilities in “Landscape Paleopedology” have recently been opened up by the development of Geographical Information Systems (GIS) and related software, which enables modeling of the present and past topography and pedostratigraphic levels. Modeling allows reconstruction of morphodynamic processes as response to tectonic and climatic variability (Napoli et al., 2006, Costantini et al., 2007a, Costantini et al., 2007b and Miller et al., 2009) as well as understanding differences in pedogenesis as a result of mineralogical heterogeneity of the parent material (Delarue et al., 2009). Further developments are expected by new interdisciplinary approaches, integrating geographic, pedometric, pedological, and geochemical methods, which may enable (e.g.) modeling of soilscape development over time. Some recent studies already point in this direction, combining models of rock weathering with soil formation and soil distribution in the landscape (Minasny et al., 2008 and Samouëlian and Cornu, 2008). 6. Heritage soil documentation and protection Paleosols store information about the environmental conditions during their genesis and thus reflect the natural and cultural heritage of the landscape. This particular nature of paleosols, referred to as “soil memory” (Targulian and Goryachkin, 2004), makes them particularly valuable among the various earth soil bodies. The work of Costantini and L'Abate published in this volume points to the “cultural or natural heritage” of soils. The growing interest in this concept is reflected by the recent decision of the International Union of Soil Sciences to set up a Working Group on Rare Soils and Heritage Soils. The Council of the European Union considers preservation of soil as a part of natural heritage by the document “Council Conclusions on Integrated Soil Protection” (Brussels, 18 July 2002) and by the final document “Thematic Strategy for Soil Protection” submitted in September 2006. In addition, the protection of the soil's cultural heritage is closely linked with the European Landscape Convention of the Council of Europe which aims on preserving historical landscape elements. Several local governments, organisations and scientists have started research on soil heritage (see e.g. Costantini et al., 2007a, Costantini et al., 2007b, Towers et al., 2008, Vancampenhout et al., 2008 and Ibáñez et al., 2009). During the last decades, however, the area of heritage soils in Europe has dramatically decreased, mainly because land use planners and policy makers do not know about their existence and because no tools to indicate the value of heritage soils are available. A tool to evaluate and manage heritage soils is thus required to enable protection of these soils in Europe. The paper by Costantini and L'Abate presents a methodology to evaluate heritage soils of Italy, and to establish a specific geodatabase, which may be used also in other countries. The issue of heritage soil preservation is closely related to that of pedodiversity, which is defined as the variation of soils in an area (41a, McBratney, 1992, Ibañez et al., 1995, Phillips, 2001, Phillips and Marion, 2005, McBratney and Minasny, 2007 and Guo et al., 2003). As demonstrated in the paper of Costantini and L'Abate, paleosols form an important part of pedodiversity of a country, which underlines the importance of making their existence public. It is therefore recommended that an international scientific effort is made towards evaluation, documentation, awareness raising and protection of heritage soils and pedodiversity.