Palaeoecology

WHAT IS PALAEOECOLOGY?
Palaeoecology, strictly speaking, is the study of the nature and timing of environmental changes in the past, including climate change, assessing the impact of human activities on the natural environment and attempting to disentangle human impact from natural variability.
WHAT IS PALAEOECOLOGY?
Archaeological Science is a generic term used to describe various applications of scientific techniques to the study of the past.
This is an extremely broad field and incorporates:
Studies of ancient metals, e.g. how they were manufactured, sources of metal
The sources of various materials, such as stone, by analysing their petrologies
The identification of the organic fraction of any archaeological material (e.g. as tissue or fibres) and it’s subsequent analysis
The study of the chemical composition of materials for various purposes
ASPECTS OF PALAEOECOLOGY
Wood Studies, e.g. Dendrochronology, but also charcoal and fossil wood.
Palynology: Pollen, also Melissapalynology (study of pollen in honey)
Plant macrofossils: charred seeds and grains
Microfaunal studies
Coleoptera (Beetles), also other insects
Molluscs
EXAMPLE OF AN INTEGRATED PALAEOECOLOGICAL STUDY
Lisheen Mine Archaeological Project
Edited by M. Gowen, J. Ó Néill and M. Phillips
Published by Wordwell in 2005
Palynology
This is the study of fossil tree pollen preserved in buried soils and recovered from a context that can be dated or understood to have some significance.
Samples are collected by taking a continuous sample of material from a suitable environment such as deposits of peat or silts.
The sample is then divided up into small sections of even width (e.g. 1 cm) and this subsample is then processed to recover any surviving organic material.
The individual pollen grains are then counted and identified.
Palynology
Pollen grain (Lily)
Palynology
Pollen grain (Willow)
Palynology
Pollen grain (Pine)
Palynology
Dating Pollen Sequences
After counting and placing the pollen data into a chronological sequence, the main characteristics are studied so that general phases can be identified.
Some key events, such as the Elm Decline around 4300 BC are used as broad markers for events.
Once a phased sequence has been created, dates are obtained from suitable material.
On-line European Pollen Database
http://www.ncdc.noaa.gov/paleo/epd/epd_main.html
Drawback is that it is not completely up-to-date.
A Sequenced Pollen Diagram
A Sequenced Pollen Diagram
Dating Tree Pollen Summary Phases
Depth
A Sequenced Pollen Diagram: Phasing
Phasing is very straightforward
It is usually labelled separately for each sequence that has been studied
A Sequenced Pollen Diagram: Summary
Usually a summary is presented indicating the relative percentage of tree, shrub and herb pollen that is present.
This is important for understanding variations over time.
A Sequenced Pollen Diagram: Trees and Shrubs
Trees listed include:
Betula/Birch
Pinus/Pine
Ulmus/Elm
Quercus/Oak
Tilia/Lime
Alnus/Alder
Fagus/Beech
Fraxinus/Ash
Corylus/Hazel
Salix/Willow
Ilex/Holly
A Sequenced Pollen Diagram: Dates and Depth
The main unit of measurement for all pollen sequences is actually depth or location within the sample.
Subsequent study can identify tephra (glass particles) from dated volcanic eruptions that allow portions to be dated.
Organic material can be used to supply a sample for radiocarbon dating.
Elm Decline
This diagram shows species declining such as Elm (Ulmus) and Pine (Pine) and other such as grasses (Graminae) and heather (Calluna) exanding, c.4300 BC.
Pollen Diagram: Herbs and Mosses




In many cases the same broader patterns are visible across Ireland (here, Longford and Tipperary) suggesting the same basic vegetation history.
Often these relate to patterns of clearance (by humans) or regeneration (suggesting abandonment).
There is always some minor variation in this (compare the patterns above).
For long periods, though, the vegetation history is very similar – such as the regeneration in 600-200 BC, and, between AD 50 and 400 above.
Testate Amoebae
Help identify moisture levels.
Difference species indicate depth of water and hydrology.
This can tell us about relative amounts of rainfall and sunshine.
Note the scale:
1000 microns=1 mm
Testate Amoebae and Water-tables
These are the results of studies from Derryville Bog in County Tipperary. The line beside each column indicates the depth of the water-table below the surface of the bog (as indicated by the types of Testates present).
Water-table depth
Where the line is close to the column, the ground is wet.
Where it is not, the ground is dry.
At Derryville a period of low water table (i.e. dry bog surface) from AD 200 to 500 coincides with a gap in the dates for trackways suggesting the bog was dry enough to walk without needing to build trackways
Plant macrofossils
Plant remains often survive in waterlogged deposits.
This can include leaf and stem fragments as well as grains and seeds.
Charred seeds and grains also survive as they are robust after being carbonised.
Sometimes, though, only the impression survives, such as on a potsherd.
Burnt and unburnt wood can be studied
Studies of wood can show how wood was exploited in the past.
Comparison of different areas at Derryville showed human impact on woodlands.
Burnt and unburnt wood can be studied
This material (and the last slide) showed the composition of the woodlands to the east of Derryville and that they were being felled and used.
Burnt and unburnt wood can be studied
Wood from the west of Derryville bog was being used selectively.
Certain species were being managed to produce more wood.
Others may have been felled and cleared from the woodland and then disappear.
Woodland Management
Techniques like coppicing and pollarding are used to produce hazel and willow rods for wickerwork.
In this case, comparison of the age of the wood shows a preference for wood allowed to grow for around 6 years.
Managedwood
As shown here, regular sized wood can be used much better than unmanaged wood.
Hazel can be deliberately manipulated to produce rods of a certain size for making hurdles.
Sometimes snail and insect puppae can be used to show what the environment was like such as these examples that would indicate wet ground (stagnant water):Lymnaea truncatula(dwarf pond snail), on the right; andTrichoptera (caddis fly), on the left.
Coleoptera (Beetles)
Coleoptera (Beetles)
More regularly used are beetles (Coleoptera) as they are sensitive to the type of environment in which they live.
Basic technique is to recover samples either in sequence (as with pollen) or from specific contexts.
Sample is processed in a lab and the individual fragments are recovered and analysed.
Examples of what is found are shown on the next 4 slides.



Prostomis Mandibularis (shown here) is only known from archaeological sites. It inhabited natural, unmanaged woodlands, such as covered Ireland after the Ice Age.
Prostomis
As this map shows – not only was it extinct in Ireland, but also Britain.
These finds can be significant in showing how much the landscape has changed.