Dana Pietsch

Soil developmental stages of layered Cambisols and Calcisols on Socotra Island, Yemen.

Semiarid tropical regions are very suitable to study the polygenesis of layered substrates and soils. To determine relic and recent soil features of tropical soils, pedons in the northern part of Socotra Island, Yemen, were investigated. The aim of the study was to create developmental stages of widely distributed soils, which in particular are layered Cambisols and Calcisols. In most layers of those investigated soils, denudative components occur, which clearly indicate the relocation of coverloams and coverclays with an incorporation of extraneous materials, such as small pieces of relic clayey loams with different shapes. These fragments indicate strong chemical weathering, preceding erosion, and redistribution and/or embedding into younger sediments. Calcium carbonate found at a depth of up to 30 cm in 52% of the layered soils is very typical of an increasing aridity in parts of the semiarid tropics, particularly in areas with high groundwater levels and interflow. In addition, oxidation features and clay illuviation in noncalcareous substrates were detected. At the end, two major soil developmental stages of layered Cambisols and Calcisols were defined and demonstrated at two selected profiles. We assume that patterns of soil polygenesis depend not only on the composition of the respective substrates but also on changing climate conditions. Geochemical and soil physical methods as well as micromorphological analysis were used to describe and classify the soils.

Holocene soils and sediments around Ma'rib Oasis, Yemen: Further Sabaean treasures?

The ancient cultures of Southern Arabia are increasingly recognised as playing as major a role in the heritage of mankind as the early cultures of Egypt, Mesopotamia or the Indus Valley. The beginning of the widely known Sabaean culture dates back to the end of the second millennium BC. Whereas, undoubtedly, its wealth came mainly from the trade along the Incense Road, the backbone of its economy was irrigated agriculture. Since agriculture is based on soil and water resources and, hence, land availability, the buried soils and sediments of the area surrounding the Ma’rib Oasis have been investigated, both as an archive of Holocene soil development in Pre-Sabaean times and as ‘natural treasures’, as, for example, ores or alabaster are defined. The natural buried Holocene soils around Ma’rib are rich in phosphate, organic material and volcanic ashes. In a few places they demonstrate cultivation before the Great Dam of Ma’rib was built in the first millennium BC. Most important are those soils that formed during the Neolithic between 8000 and 3000 BC, a time before the permanent settlement of humans in the Bronze Age, and before the arrival of those of the early Sabaean period at the Ar-Rub’ Al-Khali desert margin. Since the area surrounding the oasis shows a huge variety of landscapes, such as dune belts, volcanic fields with archaeological structures and different soils, it is worth accentuating the significance of Holocene soils as an important record or archive of land use. As well as classical soil analysis, AMS- 14C-datings, the results of phytolith analysis and geochemistry, including XRF data, have been taken into consideration.

Colluvial deposits - proxies for climate change and cultural chronology. A case study from Tigray, Ethiopia

Colluvial deposits can be defi ned as sediments on slopes which incorporate either unweathered material such as loess or pre-weathered material such as eroded soils, or both. In some cases colluvial deposits cover paleosols, and in many cases they serve as parent material of soil formation after their deposition. When yielding archaeological artefacts, phytoliths and datable material colluvial deposits archive cultural chronology. By the example of Tigray/Ethiopia the present contribution demonstrates the importance of the multi-proxy „colluvial deposit“, while emphasising it’s suitability for geoarchaeological and palaeopedological research. The analysis of colluvial deposits, paleosols and phytoliths in Yeha illustrate existing links between ancient land-use being part of the Ethio-Sabaean culture and different stratigraphic units. While the study of colluvial deposits provide answers on cultural chronology and land-use-changes, the study of paleosols buried by or formed within these colluvial deposits makes it possible to demonstrate Holocene climate change along the ITCZ. Zusammenfassung. Als kolluviale Ablagerungen werden Sedimente bezeichnet, die sowohl unverwitterte Hangsedimente (z.B. umgelagerter Loss) oder vorverwittertes Material (z.B. umgelagerte Boden), oder beides aufweisen konnen. In manchen Fallen bedecken kolluviale Ablagerungen Palaoboden, haufi ger noch stellen diese Hangsedimente das Ausgangsmaterial fur Bodenbildung dar. Archaologische Artefakte, Phytolithen and datierbare Materialien, sofern sie in den Sedimenten vorliegen, archivieren die Kulturepochen innerhalb der entsprechenden Umlagerungszeitraume. Das vorliegende Beispiel Tigray, Athiopien zeigt die Bedeutung des “multi-proxies” kolluviale Ablagerung und dessen Eignung fur die geoarchaeologische und palaopedologische Forschung. Dabei macht die Analyse der Sedimente, Palaoboden und Phytolithen in Yeha die bestehenden Beziehungen zwischen der Landnutzung in der Athio-Sabaischen Periode und verschiedenen stratigraphischen Einheiten deutlich. Wahrend die Erforschung kolluvialer Ablagerungen Anworten auf Fragen der Kulturchronolgie und des Landnutzungswandels bereitstellt, gibt die Untersuchung der Palaoboden Einblicke in den Holozanen Klimawandel entlang der ITCZ.

Buried soils in the context of geoarchaeological research—two examples from Germany and Ethiopia

Pedology is a discipline with a wide range of applications in geology, geomorphology, archaeology, geoarchaeology and geography. Especially paleopedology aims are to answer questions about climatic changes, rates of pedogenic processes, pedostratigraphy, suitability of former surface soils and human occupation. In combination to other disciplines, pedology aims to advance geoscientific methods at different scales, and during the last decades, (paleo)pedological research increasingly touched archaeological fields whereby soil research was mostly somehow included in geoarchaeology. When the term ‘archaeopedology’ was introduced in the 1940s, researchers were already aware of the importance of the subject ‘soil’ as being a key figure when answering questions of site formation history, cultural chronology and environmental change. The present paper aims to reintroduce this term to the scientific community and to accentuate the importance of buried soils within geoarchaeological research. Shown by two different studies, one from Upper Palaeolithic sites in the Ueckermünder Heide/Germany and one from ancient Yeha/Ethiopia the archaeopedological approach highlights the importance of pedological research on- and off-site excavations by clearly bridging a gap between archaeology, geoarchaeology and (paleo)pedology.

Modern and Ancient Knowledge of Conserving Soils in Socotra Island, Yemen

At first view, soil erosion on Socotra Island, Yemen would seem to be a minor problem. This appraisal is based on the fact that on the one hand the island is poor in soil resources, and on the other hand research on the island has to date focussed on biodiversity. However, results of soil investigations on Socotra showed that in the Homhil Protected Area land degradation in terms of erosion due to soil structure deterioration and humus loss has increased drastically: within 3 years a loss of about 40 m3 in a single gully head was estimated. Soil loss inevitably involves uprooting of trees and a decrease in soil fauna. Biodiversity is, of course, the most important argument for protecting the unique floral and faunal richness of the island, but what would terrestrial biodiversity be without soils? The present approach relies on a “down-to-earth” system of soil monitoring, based on both modern and ancient knowledge and oriented towards current environmental and political objectives. It should be understood as a first step towards conserving soils and vegetation in a Protected Area of this tropical island.

Soil micromorphogenesis and Early Holocene paleoclimate at the desert margin of Southern Arabia .

En los margenes del desierto Ramlat as-Sab’atayn, cerca de Ma’rib (Yemen), se encuentran paleosuelos del Holoceno Inferior bien conservados que se documentan con datos micromorfologicos y edaficos. Los suelos enterrados, representados por horizontes Ahb, indican que se formaron mayoritariamente antes de hace 8,3 ka. Por el contrario, los sedimentos arenosos que los cubren sin rasgos de edafogenesis se depositaron posteriormente debido a una aridez creciente hasta hace 6,6 ka. Los rasgos micromorfologicos de los sedimentos arenosos estan caracterizados por una microestructura granular sencilla, una fabrica birrefringente cristalitica, presencia predominante de sideromelana fresca y remanentes de microlaminas. Los horizontes Ah enterrados tienen una microestructura en bloques subangulares, una fabrica birrefringente no diferenciada como resultado del enriquecimiento en materia organica y del proceso de descalcificacion, y la presencia predominante de sideromelana completamente alterada. La mayoria de estos horizontes estan casi descalcificados, por lo que en algunas partes se observa una fabrica birrefringente de motas en mosaico y revestimientos de arcilla neoformada como resultado de una fuerte meteorizacion y edafogenesis. Los datos edaficos aportan informacion importante sobre las fluctuaciones climaticas del Holoceno, en particular la cantidad de precipitacion calculada a partir de los datos geoquimicos de los horizontes enterrados A, AB y B. Los paleosuelos enterrados indican condiciones de un clima humedo con precipitaciones que varian entre 400 y 600 mm ano-1.

Mubarak’S Garden. Land Improvement on a Dry Tropical Island in the Arabian Sea

Abstract Inhabited dry tropical regions are principally seen as vulnerable areas, especially if people have limited access to suitable land, fresh water and crop seeds. From the traditional, but also from the scientific point of view in some cases, it might be considered to be exceptional, indeed pointless, for people to try to improve land in such an arid environment. But for people living directly on a hypersaline coastline, experiments in crop cultivation are necessary to produce additional fruits and vegetables, using either traditional or adapted techniques of land cultivation. Soil investigations in a kitchen-garden situated on the northern coast of Soqotra Island, Yemen, show that one year of cultivation increased Corg contents from 0 up to 0.7%, and Pav contents from 100 mg kg-1 up to 230 mg kg-1 in the garden beds. A general decrease in slightly soluble salts - explained by irrigation with fresh water - is already obvious after only one year: decreasing from 6.7% slightly soluble salt in marine sand, to 0.3% slightly soluble salt in cultivated beds. A vertical increase of clay content in sediments and soils, and also an inland increase of clay content, was observed. It is hoped that this example will encourage future research on kitchen-gardens, since they have a beneficial effect on society as well as having positive environmental consequences, as seen in the present case of land improvement on Soqotra Island in the Arabian Sea