Hans-Rudolf Bork

Quantifying historical gully erosion in northern Bavaria

The Wolfsgraben is one of many ravines that cut into the silty–sandy material of the Triassic benchlands of northern Bavaria, Germany. Within the research area, a gully—several meters in depth—has carved in to a bluff 500 m west of the upper Main valley. An analysis of 17 exposures and 30 drillings was conducted within the gully and its colluvial fan in order to reconstruct the soil formation, extreme rainfall events and land use changes throughout history. Detailed field studies, chemical soil analysis, dating methods of charcoal and pottery, as well as written documents were combined to produce a high-resolution stratigraphy. Nine main phases of landscape evolution, caused by extreme rainfall, runoff and soil erosion in agriculturally used areas, have been identified since the medieval period. The highest amount of soil loss occurred during 14th, 18th and 19th centuries, a result of intensive land use. Climate changes affected the intensity of rainfall and the magnitude of soil loss during these periods. D 2003 Elsevier Science B.V. All rights reserved.

Prehistoric and early historic agriculture at Maunga Orito, Easter Island (Rapa Nui), Chile

A long section adjacent to a former obsidian quarry on Easter Island (Rapa Nui) reveals a sequence of agricultural strategies, beginning with the clearing of palm trees in the twelfth century AD, and the making of an open garden growing yams and taro, that continued through the fifteenth century. The later phases between the seventeenth and nineteenth centuries include veneer and boulder gardens that reflect the broader strategy employed by the islanders to fight the increasingly arid soil.

Vineyards, hopgardens and recent afforestation: effects of late Holocene land use change on soil erosion in northern Bavaria, Germany

Human impacts on soil erosion and landscape evolution during the late Holocene were quantified in a small catchment near the city of Bamberg in northern Bavaria, Germany. Along the valley of the Wolfsgraben, a 400-m-long ravine, a gully has been incised to a depth of 3 m into colluvial sediments. Field investigations and historical data are used to appraise geomorphic responses to land use changes. The first settlements in the region existed around 5000 BC. With the foundation of the Diocese of Bamberg in 1007 AD, more and more land was cleared. In the Wolfsgraben, vineyards, hopgardens and intensive forest use increased soil erosion resulting from heavy rainfall events. Highresolution stratigraphy, with archaeological dating of pottery and 14 C dating of wood and charcoal indicated two main periods of gully erosion: during the 14th and in the late 18th and early 19th centuries AD. Almost 5 m of colluvial sediment cover the Triassic sandstone in the Wolfsgraben today. Land use changed with population density, hop production and decreasing soil fertility. Today, almost the whole catchment and the surrounding hills are covered with forest. D 2002 Elsevier Science B.V. All rights reserved.

Fire and forest history of central European low mountain forest sites based on soil charcoal analysis: The case of the eastern Harz

Long-term environmental changes in some areas of Central Europe are still poorly documented due to the lack of archives suitable for well-established paleoecological approaches. However, paleorecords of such areas would provide important insights into the Holocene vegetation history of Central Europe. To contribute to fill this gap, we conducted soil charcoal analyses to investigate fire and forest history for the eastern Harz Mountains (Germany). Soil from 15 sequences at three investigation sites was analyzed, and charcoal assemblages were extracted. The taxonomic analysis shows Holocene woodland composition changes, from post-glacial pioneer woodland, dominated by pine, to broad-leaf closed forests, dominated by oak, and succeeded by beech. The temporal distribution of accelerator mass spectrometry (AMS)-14C datings of single charcoal pieces indicates that fire events occurred regionally synchronous, mainly in the late-Pleistocene/early-Holocene and late-Holocene periods. The radiocarbon dating is supported by the description of the sampled soil sequences, which permits the identification of late-Pleistocene/early-Holocene in situ formed soil horizons, as well as evidences late-Holocene erosion-sedimentation processes. Climate seems to have triggered late-Pleistocene/early-Holocene fire events. In contrast, the increase of fires, at both local and regional scales, during the late Holocene in low flammable broad-leaf forests is interpreted as related to human activities. Finally, it is highlighted that the species spectrum of the extracted charcoal assemblages and the radiocarbon ages obtained fits regional and over-regional data, also concerning the soil charcoal concentrations that appear to be included in regional and global ranges of soil charcoal pools.

Changing Human Impact during the Period of Agriculture in Central Europe: The Case Study Biesdorfer Kehlen, Brandenburg, Germany

The onset of agricultural practices during the Neolithic Times brought about significant changes in the environment. Woodland clearance and subsequent farming facilitated soil erosion. Run off, caused by heavy rainfalls could erode the soils on the bare arable land. The accumulation sequences of these soil erosion events can be found on colluvial fans of gullies or in small sedimentary basins. These sedimentary records can be investigated using four dimensional landscape analysis. In Central Europe peaks of soil erosion due to human impact have been reconstructed for the Bronze Age, the Iron Age, late Medieval Times and Modern Times (Bork et al., 1998). The example of the Biesdorfer Kehlen in Brandenburg, Germany, shows that three main phases of land use induced gully erosion and hill slope erosion from prehistoric times until 1991 happened. From the Iron Age until early Medieval Times a stable period of three-thousand years with intensive soil formation indicates the absence of farming in the investigation area. These investigations, together with the quantification of landscape changes, can help to obtain better knowledge of past and possible future impacts of agriculture on the landscape. The data may also be used to validate soil erosion models and landscape evolution models.

The influence of historic land-use changes on hillslope erosion and sediment redistribution

Agricultural societies around the world have dramatically altered the natural landscape, particularly through accelerated soil erosion. The expansion of agricultural land use into steeper headwater areas during the Medieval period in central Europe is known to have caused large increases in soil erosion and sediment redistribution downstream. Although land-use practices changed and improved following this initial impact, it is currently unknown whether changes in land-use techniques also improved hillslope soil erosion and sediment redistribution rates. In this paper, we use a variety of techniques, including chrono-stratigraphy, wood charcoal analysis and a geostatistical model, to reconstruct land-use and erosion rates for the period spanning the Medieval Period to the present (1100–300 years ago) in a small headwater catchment in central Europe. Coupling land-use, hillslope erosion and sediment redistribution fluxes, we find the largest flux change occurs because of the initial deforestation at the beginning of the Medieval Period (1100 years ago). Following deforestation, we identified three main types of land-use techniques that were practised between ~1100 and 300 years ago: Horticulture, cropping agriculture and rotational birch silviculture, the last of which represents the earliest evidence for this practice found in central Europe to date. However, we find only small differences in hillslope fluxes throughout the catchment despite the variable land-use techniques employed. This is because the land-use techniques primarily influenced and increased the hillslope sediment storage capacity rather than erosion rates directly, which is an important distinction to consider for future work attempting to link changes in human land use and hillslope erosion.

Dynamics and driving forces of agricultural landscapes in Southern Ethiopia – a case study of the Chencha and Arbaminch areas

Agricultural landscapes in Ethiopia have undergone unprecedented changes. The direction of change, however, is unsustainable as manifested in land degradation, biodiversity loss, and low agricultural productivity. The objective of this study is to examine the patterns and trends of agricultural landscape development and responses of the local people within the framework of the dynamics of demography, socioeconomic conditions, politics, and natural resources in the Chencha and Arbaminch areas, Southern Ethiopia, during the last century. Information on cultivated and grazing land areas was acquired by satellite image interpretation. Interviews and group discussions provided important information on agricultural land use systems. A review and an analysis of secondary sources and documents of past studies were also used for trend analysis as a baseline and a supplement to oral history. The results show that cultivated land was expanded by 39% from 1973 until 2006, but per capita farming land holdings decreased enormously. In the same period of time, grassland shrank by 69% thus causing a significant decrease in livestock. Cultivated land scarcity can mostly be related to demographic pressure, which was exacerbated by government policy, land tenure, and the nature of subsistence agriculture. The farmers, however, were resourceful and developed skills over millennia to cope with the problems associated with population density and scarce resources. However, these traditional land use activities and land management practices have been deteriorating recently. Land use planners and environmental managers should take local knowledge and innovation into account in order to make sound decisions for the future.

Anthropogenic influence on rates of aeolian dune activity within the northern European Sand Belt and socio-economic feedbacks over the last ~2500 years

In North-Western Europe, Pleistocene sand sheets have been reactivated during phases of Holocene deforestation and agricultural land use. Although there are temporal overlaps between anthropogenic activity and sand sheet reactivation, the root cause and subsequent feedbacks between aeolian activity and societal response remain largely unknown. Here, we seek to establish cause and effect by examining the detailed co-variation in both timing and magnitude of aeolian and anthropogenic activity through the quantification of Holocene dune sediments in combination with archaeological and pollen records. These records indicate a series of complex phases of aeolian activity followed by landscape stabilization, which we attribute primarily to changing patterns of human impact. We find that a steady increase in dune deposition rates in the Medieval Period corresponds to an increase in settlement activity and deforestation (~AD 1000–1500). At their peak, Medieval deposition rates were 3.4 times larger than during the late Pleistocene, the period experiencing the most favourable natural conditions for aeolian sediment transport. Prior to the Medieval Period, relative land-surface stability (represented by a depositional hiatus) persisted from the late Pleistocene until the Roman Iron Age Period (AD 0–400). Deforestation to fuel iron production had minor impact on aeolian activity, as indicated by the lowest recorded deposition rate (0.12 ± 0.02 t/ha/a). Following the Medieval Period peak in deposition rates, aeolian activity diminished rapidly and coincided with the abandonment of nearby human settlement. This sequence of events provides evidence of a direct positive feedback in which Medieval agricultural overexploitation favoured aeolian activity that rendered the landscape practically unworkable for cropping agriculture. Based on our findings and a comprehensive review of Northern European sand belt activity, we interpret a very high sensitivity of aeolian activity to past and present human impact and argue that unsustainable land-use practices have been the cause for widespread settlement abandonment.

Natur zwischen Wandel und Veränderung — Phänomene, Prozesse, Entwicklungen

Wahrend der zuruckliegenden Jahre hat sich das Naturbild innerhalb der verschiedenen mit okologischen Themen befassten Disziplinen grundlegend geandert. Als wesentliche Merkmale okologischer Systeme gelten Dynamik und Verschiedenheit in Zeit und Raum. Bislang wurden diese Erkenntnisse jedoch im Umwelt- und Naturschutz viel zu wenig rezipiert mit der Folge einer immer noch uberwiegend statischen Naturbetrachtung: Wandel und Veranderung sind Merkmale der Natur in Vergangenheit, Gegenwart und Zukunft.

Interpretation of prehistoric reddish pit fillings on Easter Island: A micromorphological perspective

In the context of geoarchaeological investigations on Easter Island several hundred human-made pits filled with reddish silty material were discovered in fluvial terraces of two valleys on the southern slope of Maunga Terevaka, the highest volcano of the island. Micromorphological analysis of one representative pit filling and comparison of its geochemical and physical properties with sediments in the surrounding terrace was performed in order to reconstruct the probable formation and use of the material in the pits. A hypothesis of pigment production by heating of minerogenic iron-rich substrate with grass fuel resulting in formation of hematite is suggested. It is assumed that the pits represented the places for production and storage of the pigments, which were used by Rapa Nui for cultural and ritual purposes. The ongoing interdisciplinary research will enhance the interpretation of the pits and their fillings and contribute to a better understanding of cultural development on Easter Island.