Kevin J. Edwards

Microscopic charcoal as a fossil indicator of fire

Abstract Charcoal preserved in lake sediments, peat, and soils provides a record of past fire occurrence. An understanding of fire history is important in evaluating interactions between vegetation, climate and human disturbances through at least the last several millennia. In this paper we review information concerning the production, dispersal, sedimentation and preservation of charcoal. We present examples of studies that have used charcoal analysis in palaeoecological reconstructions, with special emphasis on analytical techniques and problems of interpretation. Unlike pollen, which is produced continuously in fairly constant amounts, charcoal is produced in large quantities but at irregular intervals. These are a function of fire regimes that are often unique to specific vegetation types and/or climatic regions. Charcoal particles vary in size from sub-microscopic to macroscopic, with small particles presumably being transported further by wind and water than large particles. Charcoal preserves well, but it may be subject to breakage, especially when transported by water. We present theoretical models of dispersal and discuss potential problems associated with post-depositional mixing. A variety of charcoal analysis techniques have been employed during the past four decades. Most involve microscopic identification and quantification of numbers or size of individual fragments occurring in samples prepared for pollen analysis. The most commonly used method — estimating charcoal area by categorizing particles in several size classes — is both tedious and time consuming, and recently introduced techniques attempt to estimate past fire occurrence based upon point count estimation, elemental carbon analysis, magnetic measurement of sediments, electron microscope, and spectrographic analyses. A lack of standardization both within and among analysis techniques has hampered interpretation of charcoal profiles. Taphonomic processes affecting charcoal are less well understood than for pollen, and as a result interpretations of historic interactions between vegetation and fire based upon pollen and charcoal analyses are difficult. We review several studies through which advances have been made and suggest questions for future study.

Lake sediments, erosion and landscape change during the Holocene in Britain and Ireland

Abstract Lakes are excellent repositories of air-borne and especially stream-borne materials. It has long been recognised that lake sediments contain a strong record of catchment soils via the inputs of minerogenic and chemical erosional products. To these may be added a variety of palaeoecological indicators including pollen, fungi, Sphagnum leaves and faunal remains. Pollen analysis, in particular, enables land use change to be assessed over many millennia and demonstrates the landscape impacts of woodland clearance, grazing and crop cultivation. Radiocarbon dating provides a chronology for environmental and agricultural change and acts as an indicator of erosion in its own right. The use of such indicators to reconstruct past instances and patterns of erosion is demonstrated with reference mainly to 50 British and Irish lake sites and especially those which have produced signals of erosion in the form of accelerated sediment accumulation and inversed or reversed sequences of radiocarbon dates during the mid and late Holocene. Sites displaying even or decreased sedimentation through time are concentrated in northern and northwestern Scotland and have either no clear signs of human impact, or only so towards the latter part of the Holocene. This pattern probably reflects a combination of factors including low population densities, thin soils and the ‘sealing’ effect of blanket peat. In contrast, all sites with accelerated erosion have indications of anthropogenic impact. This is often prior to levels of increased sedimentation showing a delay in system response. While the spread of dates for the start of the rise in sediment accumulation spans 6200–940 BP, three clusters are evident at 5295–4970, 4530–4235 and 2980–2810 BP. Radiocarbon inversions (mostly reversals) are evident for 18 sites. No obvious causal patterning is indicated and they probably demonstrate no more than the fact that catchment soils, including peats, around a particular site were pushed beyond an erosional threshold sufficient to ‘age’ the sediments deposited within the lakes. It is hoped that improvements in data quality will allow the refinement of such exercises in the future and that lakes will be valued as repositories of long-term landscape sensitivity.

Palynological and temporal inference in the context of prehistory, with special reference to the evidence from lake and peat deposits

Abstract There is an increasing use of palynological data to infer prehistoric agricultural activity. The uncritical acceptance of the technique of pollen analysis by archaeologists and palynologists is questioned. Attention is focussed upon the nature of clearance activity and problems of its inference from pollen spectra; the spatial distribution of palaeoenvironmental sites; and the proximity of such sites to those of prehistoric activity. The resolution apparent in peat and lake sediment pollen profiles together with problems of dating and temporal inference, are examined. In response to a perceived lack of formalization in palynological research, some simple models of clearance activity are presented. The complexity involved in environmental reconstruction is emphasized by reference to the use of supplementary data to augment the orthodox pollen record.

Cereal pollen grains in pre-elm decline deposits: Implications for the earliest agriculture in Britain and Ireland

Abstract Evidence of cereal type pollen grains in the pre-elm decline sections of pollen profiles is demonstrated from five sites in Ireland and three in Britain. Technical and archaeological considerations are also discussed. It is concluded that cereal cultivation in the British Isles occurred before the traditional beginnings of arable activity as denoted by the elm decline, and that the palynological data should be seen to underline caution in referring pre-elm decline pollen changes to Mesolithic disturbance.

Palaeoecological and historical evidence for manuring and irrigation at Garðar (Igaliku), Norse Eastern Settlement, Greenland

Palaeoenvironmental data are presented from the site of Garðar (modern Igaliku), the location of the cathedral and the bishops farm in the Norse Eastern Settlement of Greenland. The latter was founded from c. AD 985 and abandoned some time during the fifteenth century. Inspection of drainage ditches located in close proximity to the settlement ruins revealed inter alia an organic-rich unit containing cultural debris (worked wood, animal bone, stone and charcoal) dated by AMS radiocarbon dates on seeds to the period c. AD 1110—1370. Fossil insect and pollen assemblages contained within the deposit appear representative of natural environments (primarily wet eutrophic meadows) but are mixed with high frequencies of a range of synanthropic insects, including human and animal ectoparasites that could only derive from indoor habitats. This is strongly indicative of the manuring of fields with waste from houses and byres in order to increase yields of hay. Large amounts of hay would have been necessary to provide winter fodder for the bishops herd of cattle — the largest known in Norse Greenland — and dung from these animals seems likely to have been a significant component of the material used to fertilize the fields. The process of spreading the manure at Garðar was probably integrated with the careful manipulation of water resources across the site, indicated by the presence of a network of irrigation channels and dams in the archaeological record, and comparisons are drawn with similar systems elsewhere in Mediaeval Europe.

Holocene palynology: II human influence and vegetation change:

Much palynological research has focused upon the role of humans in influencing the development of vegetation. This continues to be the case in Europe and anthropogenic studies in pollen analysis now extend to most parts of the world. An attempt is made to present some of the major research published between 1985 and mid-1991. The material selected represents a broad range of palynological applications and geographical areas. Methodological aspects include fine resolution, spatial and absolute pollen studies. Area studies concentrate upon Europe (with particular emphasis on the Corylus maximum, the Alnus rise and the Ulmus decline horizons in northwest European pollen diagrams), and to a lesser extent on North America, although available literature from other continents is also examined. It is concluded that a relatively small quantity of literature is devoted to methodology, but that it points the way to likely advances in elucidating human involvement in vegetation change. Fine resolution investigations may enable temporally precise changes in pollen spectra to be discerned and hence remove some of the inadequacies of coarse sampling procedures. Spatial studies reveal the complexity of palaeovegetational landscapes and the role of humans in their disturbance. Optimizing methods in the detection of cereal-type pollen grains provides challenges to both palynologists and archaeologists concerning the evidence for early agriculture. The potential of absolute data in examining human activity in forested areas is also shown. The palynological demonstration of hunter-gatherer and agricultural impacts beyond Europe is welcomed. The increasing use of microscopic charcoal data for investigating fire-vegetation relationships in cultural contexts is promising.

The longevity of pastoral episodes of clearance activity in pollen diagrams: the role of post-occupation grazing

The detection of features equated with anthropogenic clearance activity in pollen diagrams has become a commonplace. Research in Britain and Ireland has shown that episodes related to pastoral activity may be of many centuries duration throughout the prehistoric and historic periods. Although several workers have suggested that clearings in the forest cover may be kept open by grazing animals, it has not been proposed that such a mechanism could be responsible for extreme clearance phase longevity. Reference is made to historical and recent evidence of animal husbandry and natural herbivore patterns of exploitation. It is suggested that post-occupation grazing in particular might offer a satisfactory explanation for the phenomenon of long-term pastoral longevity in

The European Modern Pollen Database (EMPD) project

Modern pollen samples provide an invaluable research tool for helping to interpret the quaternary fossil pollen record, allowing investigation of the relationship between pollen as the proxy and the environmental parameters such as vegetation, land-use, and climate that the pollen proxy represents. The European Modern Pollen Database (EMPD) is a new initiative within the European Pollen Database (EPD) to establish a publicly accessible repository of modern (surface sample) pollen data. This new database will complement the EPD, which at present holds only fossil sedimentary pollen data. The EMPD is freely available online to the scientific community and currently has information on almost 5,000 pollen samples from throughout the Euro-Siberian and Mediterranean regions, contributed by over 40 individuals and research groups. Here we describe how the EMPD was constructed, the various tables and their fields, problems and errors, quality controls, and continuing efforts to improve the available data.

Bronze Age myths ? Volcanic activity and human response in the Mediterranean and North Atlantic regions

A first rule of statistics is that the existence of a correlation does not itself prove a causal connection. This is the heart of the recurrent question in later European prehistory -whether in the Mediterranean or in the Atlantic northwest - about volcanic eruptions, their impact on climate, and then of the climatic impact on human populations. The burial under tephra of the Late Bronze Age settlement of San torini is proof of a particular catastrophe: but is there the evidence to prove wider European calamity?

Stable oxygen isotope and pollen records from eastern Scotland and a consideration of Late-glacial and early Holocene climate change for Europe

The presence of marl deposits belonging to the Lateglacial period in a former lake basin at Lundin Tower in Fife, Scotland has allowed palaeoenvironmental investigations by means of carbonate δ13C and δ18O, and organic matter δ13C, in addition to palynology. The variations that emerge reveal strong similarities between the pollen and isotope records and these are interpreted as reflecting climatic shifts. The classic Late-glacial pattern of Oldest Dryas–Bolling–Older Dryas–Allerod–Younger Dryas may be evident and other climatic oscillations are shown to have occurred not only during the Allerod but also in the Preboreal. The problem of the time discordance between isotopic change and pollen representation is addressed through explanations involving lags in plant colonization. A comparison of the δ18O records from 43 sites across Europe reveals two different regional patterns, which raises fundamental questions over the nature of Late-glacial palaeoclimates.