A14: The evolution of a landscape through time

Geoarchaeology and environmental archaeology in action: the story of the A14 landscape and vegetation from the Bronze Age - Anglo Saxon

Introduction

MOLA–Headland Infrastructure (MHI) were commissioned by the A14 Integrated Delivery Team (IDT), on behalf of Highways England, to undertake the archaeological mitigation for the A14 Cambridge to Huntingdon Improvement Scheme.

The A14 excavations are among the biggest and most complex ever undertaken in the UK, revealing important archaeology of prehistoric, Roman, Saxon and medieval date.

During the A14 excavations more than 9000 samples were taken for palaeoenvironmental assessment and analysis. The results of this have allowed us to reconstruct what the vegetation may have looked like from the Bronze Age through to the Anglo Saxon period.

This StoryMap presents the model of past vegetation cover along the A14 corridor. Scroll to explore the key findings and all the evidence used in creating this model.

'People, plants, animals and the material of the earth itself all play their role in shaping and being shaped by each other'

Case Studies

Case Study 1 : Brampton Woods

Slide the map divider to the right to see the modelled Bronze Age landscape and to the left to see the modelled Anglo-Saxon landscape.

Just half a mile to the west of Brampton village, the Brampton West Landscape Block (outlined in red) covered 78 hectares in the western part of the A14 excavations, predominantly on the western side of the A1 and to the south of the A14. The archaeological evidence ranged from the Neolithic period through to the 20th century.  

Present-day Brampton Woods is located just 500m from the Brampton West excavation area. It is an ancient woodland that is known to be at least 900 years old due to its inclusion in the Domesday Book (  https://www.wildlifebcn.org/brampton-wood) . Whether Brampton Wood is even older, however, is uncertain. Our research suggests that Brampton Wood is actually far older than Domesday, and it may well have its roots in prehistory.

The analysis of pollen and botany samples from the A14 project indicates that mature, deciduous wood was in close proximity to the settlement area. There is good evidence for this at least as far back as the Bronze Age (2450-800 BC), and it is likely that woods probably date to even earlier.

Across the scheme there is strong evidence of woodland management through all periods, even as far back as the Neolithic. A key indicator is the diameter and number of tree rings in charcoal found on sites. On the A14 these show indicators of stress, implying that the demand for wood resources resulted in pressure on the wood stock. This pressure appears to have increased in the Roman period. There is also widespread evidence for the use of decaying wood, indicating that higher quality wood was not always available.  

(For more information on how the Fens continued to change from the Roman period onwards see the  GREAT FENS PROJECT )

An established wood at Brampton may not have been the only such wood in the vicinity of the A14 sites. There is evidence that similar woodlands existed to the east of the River Great Ouse. These may still have been present in the Roman period but were subsequently lost. Tree throw evidence uncovered in the excavations mainly occur at Brampton West and Bar Hill. This supports what the pollen and soils suggest- that woodlands were present on higher ground with heavier soils at some point in time.

Case Study 2: Changes in the water table through the Iron Age and Roman periods

Slide the image divider to the right to see waterlogged woody terrain (carr) type vegetation. As you slide it back to the left you will see the change to more open fen type vegetation.

The floodplain of the River Great Ouse was undoubtedly an important resource throughout human occupation along the A14 sites. These wetlands would have provided various natural plant (e.g. reeds) and animal (e.g. fowl and fish) resources, but also contained land potentially suitable for agriculture.

At the end of the Bronze Age, the floodplain vegetation was of a waterlogged woody terrain (carr) with the dominate tree being alder (Alnus glutinosa). Sea level and climate changes, as well as human impacts, changed the floodplain environment during the Iron Age and into the Roman period.

The water table began to rise, making the land less suitable for alder. Environment changes would have been accelerated by increased alluviation caused by the alder dying off and the trees’ roots no longer holding the soil together. Over time the alder carr gave way to sedge/reed swamp.

This area, now being relatively open and subject to seasonal flooding, was then increasingly utilised for agriculture. Local drainage may also have been carried out to make the ground more suitable for this.

Case Study 3: The advance of agriculture

People farmed the land and grew crops in the area from the Neolithic onwards. Little is known about the first phases of crop cultivation, but in the Bronze Age agriculture was still restricted to the soils that were easier to work by hand. The light sandy soils in the area, and particularly those which have naturally higher fertility due to the local groundwater. This is shown by evidence of Bronze Age hedgerows at Conington and the absence of weeds such as stinking chamomile (Anthemis cotula), which prefer heavy soils, in the botany record.

The areas with heavy soils on the higher ground are more likely to have been open pasture to feed livestock. Grazing pressure would have also prevented woodland re-growth, as attested by the pollen records. Animal stock would have been moved seasonally between high and low ground areas using droveways like the one shown in this image.

As population increased over time the demand for land to produce crops would have increased. By the Iron Age, there is evidence of hedgerows across all landscape blocks in the A14 excavations, indicating that the landscape was extensively divided. The weed evidence also points towards crop production expanding onto the heavy soils of the floodplain.

In the Anglo-Saxon period human activity retracts to the Brampton West and Conington areas. The use of heavy soils is still apparent, however, and it seems the people of the A14 never fully reverted to concentrating only on light soils.

Understanding past vegetation

So, how did we figure all this out?

In order to unravel the past stories of environmental change along the A14 corridor we had to bring together a wide range of inter-related strands of evidence.

Lets start at the begining....

Different plants like different conditions (just like people)

Some people like it when the weather is hot, other’s prefer it cold and some even like the rain….Some love being in the hustle and bustle of a big city while others prefer more space.

Well, plants are just the same. The study of plants and their preferences is know as ecology, and by identifying the plants that are present in the archaeological record we can begin to reconstruct the past ecological conditions and, therefore, the past environment.

Ever wondered why the camelia you planted in London won’t grow or why you need to wrap your tree fern in winter? This is because most plants need specific conditions to grow. Some of the key factors in plant ecology include:

Temperature

Shade vs. light

Soil type, free draining light vs heavy, acid vs alkali, etc.

Elevation

Wetness

We know that the climate is constantly changing so how has the vegetation across the A14 changed with time?

Image reference: Ville Koistinen (user Vzb83), CC BY-SA 3.0 , via Wikimedia Commons

Find out more:

After the ice: the early Holocene climate

This map show the extent of glaciation at 23 thousand years ago (23kya) and 17 thousand years ago (17kya) (Sheffield University).

Whilst there is evidence for Palaeolithic human occupation on the A14 scheme, the vast majority of the archaeological evidence was deposited since the last ice age. The last ice age is therefore a good place to start our journey. In geological terms this was the start of the Holocene, the geological epoch we live in today. It started approximately 11,700 years ago as the ice retreated.

Just after the last ice age, the landscape of Britain would have looked very different to that of today.

Initially conditions would have been too harsh for most plants to grow but as the climate began to improve the vegetation changed. This process is known as amelioration. Some of the first studies into this process were conducted by Godwin and Tallantire ( Published in the Journal of Ecology in 1951 ) at Hockham Mere, c.75km to the north east of where the A14 crosses the River Great Ouse.

Other sites studied include Willingham Mere ( Waller et al 1994 ), just to the north of Bar Hill and archaeological excavations in the  River Great Ouse Valley  (Scaife 2000 ).

These studies take pollen (the microscopic spores that plants give off (yes those ones that cause hayfever) which become trapped and preserved in waterlogged sediments. By using the pollen to identify which plants were present, we can use the ecology of those plants to reconstruct changes in the environment.

What the pollen shows

The above locations have been subjected to pollen analysis, and they all show a similar pattern of changes in vegetation type as the climate improved over the years before present (BP):

Early Holocene

Herbaceous tundra/arctic steppe environment: Herbacious plants, with few ecological demands, become the first colonisers of the post-ice age landscape; these plants do the work and develop the soil needed to support large plants – such as trees – in the future.

Prior to 10,000 BP

The landscape remains open (devoid of trees), but the complexity and diversity of low-lying plants increases, with environments rich in herbs such as grasses and sedges. Typical species include sea plantain (Plantago maritima), meadow sweet (Filipendula ulmaria) and, possibly, mountain avens (Dryas octopetala).

10,000 BP to c. 9000 BP

As the climate conditions continue to improve the work of earlier plants pays off and rapid expansion of woodland occurs out of the few woodland refugia. The earliest colonisers included juniper, birch, pine, and hazel.

from c. 8500 BP

In a now-wooded landscape the large deciduous trees come to dominate, especially oak (Quercus spp.) and elm (Ulmus spp.).

end of the early Holocene at c. 7000 BP to 5000 BP

Oak, elm, and hazel woodland was fully established.

c. 5000 BP

Rapid decline in elm: this marked reduction in elm is recognised in pollen diagrams from across northwest Europe, caused by disease, climatic change and human activities. 

Neolithic to Romano-British period

Whilst humans were within this landscape for much of the Holocene, it is not until the Neolithic – with the advent of agriculture – that humans begin to have a substantive impact on the environment. During this time secondary woodland developed, which included species such as ash (Fraxinus spp.), holly (Ilex spp.), beech (Fagus spp.)

and hazel (Corylus avellana), while oak (Quercus spp.) and some elm (Ulmus spp.) persisted.  Alder (Alnus spp.) grew near wetlands. Herbs such as ribwort plantain (Plantago lanceolata), goosefoots (Chenopodiaceae spp.), grasses (Poaceae spp.), and cereal type pollen suggest local cereal agriculture and possibly pastoralism started during this period.

To what extent did agriculture affect the vegetation of the A14 area?

Pollen analysis on the A14

This diagram shows the complexity of the results of assessment on 257 pollen samples taken across the Scheme.

Counts of tree pollen are in green, shrubs and climbers in red, dwarf shrubs and herbs (including grasses) in yellow and aquatics in blue.  

What the pollen shows

The coloured bars at the right-end of this diagram show the cumulative representation of vegetation type cover. These bars are dominated by dwarf shrubs and herbs (yellow), indicating that the landscape was mainly open with limited tree cover. The proportion of trees (green), however, is greater for the earlier time periods (in the lower part of the diagram) albeit still only comprising 20-25% of the total.


Where were these woods?

The below map shows the areas excavated for the A14 roadworks and a 2km area around them. Click on the text for bedrock, superficial deposits, Lidar (a technology used to create high-resolution models of ground elevation) data and rivers to see what the geology and topography are like in this area. Once a 'layer' is turned on you can click on the map to find out more....

Past landscapes reconstructed: palaeo-geography of the A14

In addition to climate and the degree of light and shade, the type of plants that grow in an area are also determined by soil type (which is linked to geology) and degree of wetness (linked to elevation). Although these are less subject to change than the climate they can still vary over time due to the process of erosion and deposition of sediment and changes to the position of the water table.

The across the A14 scheme was laid down long before human occupation, and comprises Jurassic mudstones of Oxford Clay, West Walton and Ampthill Clay Formations, and Kimmeridge Clay Formations decreasing in age of deposition from west to east.

deposits are those which were deposited during the Quaternary period; the last 2 million years or so, and are of more relevance to human occupation. The main deposits across the scheme, from oldest to youngest, are:

·     Oadby Member of glacial till (turquoise)

·     River terrace deposits (orange)

·     Alluvium and peat (yellow)

If we overlay the geology map with data which shows the modern topography of the landscape we can see the Oadby Member of glacial till covers the higher ground to the north, south and west of the scheme. This till blanketed the landscape through the movement of glacial ice during the ice age.

Post Glacial Landscape

Till is an unsorted mix of sediment of all different grain sizes from clay to large boulders of rock. Notice all the which have cut into the till (light yellow areas between the brown and green). This is where the flow of water has eroded the till.

The coarse-grained sediments of sand and gravel which are heavier would have been left at the base of the valley as River Terrace deposits. The fine-grained sediment, including silt and clay, would be carried further as it is lighter. Some is deposited further downstream when the river returns to its channel after periods of flooding. Some would make it all the way to the coast in suspension where it is deposited into salt flats when the fresh water meets with the saline sea water.

Check out the geology in your area here:

How has the landscape changed since the end of the ice age?

This image shows a model of the early Holocene topography in areas around the A14 excavations. Blue indicates areas of low ground more liable to flooding and brown shows higher ground.

This gives us an idea of what the topography would have been like at the start of the Holocene and where the river channels were.

These models are created based on the deposits seen in cores collected as part of the construction design assessment.

However, they are only accurate in the areas where cores were collected from and erosion is difficult to estimate. So while these models give us an idea of what the landscape may have looked like we need to remember they probably don’t show us everything.

But they do help us think about these questions:

How has the hydrology changed?

Which areas were regularly flooded?


Bringing all the information together

By combining information from geology maps, Lidar data, soil maps, pollen analysis and plant macrofossils with what is known about the preferences of habitats for different plants it has been possible to estimate what the most likely natural vegetation would have been in the wider landscape.

Soils

The pale green areas on this map are areas of higher ground with lime rich soil which could have supported mixed decidous woodland.

The yellow areas show light free draining soils with low fertility on terrace gravels. The lower water content in these areas means that are more likely to have been naturally open grasslands.

The orange areas are also free draining soils but with high fertilitiy. These areas would have been easiest, and therefore most likely the first, areas to farm.

The dark green areas are on the floodplain and are the ones most likely to have altered through the Holocene.

Wetlands

Looking at the river courses and topographic modelling such as that shown in the previous slides, as well as the extent of modern alluvium, it is possible to estimate the approximate location and extent of wetland areas.

During the Bronze Age period this would have represented areas of wet, alder woodland (green). But as the lower areas flooded in the Iron Age then began silting up throughout the Iron Age period and into the Roman period this area would have become increasingly open with sedge type vegetation.

Other areas of marshy ground are indicated by looking at where there is no slope in the landscape which would allow pools of water to form. Some areas which were excavated also reavealled the remains of old river channels (palaeochannels).

Woodland

Pollen travels great distances which vary depending on the species of plant, this and other factors is accounted for by using numerical modelling.

From the pollen diagram shown prevciously, we know that roughly 25% of this area was woodland in the Bronze Age period.

From the different landscape blocks it has been possible to get an idea of where mixed deciduous woodland was most likely present, shown in dark green.

Further modelling was also possible for the Iron Age and Roman periods which shows the wider landscape was relatively open with just 8-12% woodland coverage.

Bunting J (2022) A14 pollen data: initial REVEALS analysis to assess past landcover – initial notes

Read on to find out more....

Open ground

We know from the pollen that the area around the A14 was persistantly open from the Bronze Age to Anglo Saxon periods.

By looking at all of the evidence together it has been possible to identify different types of open vegetation and where they are more likely to have been present.

This map shows the location of all the palaeoenvironmental samples analysed as part of the A14 post excavation work.

The archaeobotany samples (green) and charcoal (white) taken from features in the excavations preserve material from plants that were grown for agriculture.

Sometimes weeds are also included which helps us work out where different crops were being grown.

Read on to find out more....

The detail

The above sections present the key findings and the methodology. Below are the full vegetation models for each time period (Bronze Age, Iron Age, Roman and Anglo Saxon) with more detail.

The Bronze Age

Woodlands and early agriculture on light soils.

Alder woodland

Alder woodland. Click to expand.

During the Bronze Age period the valley base would have represented areas of wet, alder woodland. However, this only accounts for about 8% of the total area and the pollen evidence shows woodland covered up to 25% of the area during the Bronze Age.

Deciduous woodland

Deciduous woodland. Click to expand.

Other areas of deciduous woodland would likely have been present on the higher ground with lime rich soils.

Open vegetation

Open vegetation. Click to expand.

The rest of the area would have been 'open'. This includes, scrub, grassland and areas of agriculture, both pasture and arable. But being able to identify where these different types of open land were is even more difficult.

The banks of the River Great Ouse

The banks of the River Great Ouse. Click to expand.

West of Ouse was a focus of Bronze Age activity and the botanic evidence from cremations in this area shows the immediate area around the cremations was wet with clover indicating pastureland nearby and Rumex indicating some grasses on sandy soils. Pollen analysis on samples from River Great Ouse (on the east bank of the river) identified large amounts of microcharcoal suggestive of woodland clearance and management. It is likely that agriculture was initially focused on the terrace gravels extending along the contact between these and the floodplain edge where wet, open ‘alder’ woodland was present.

Fenstanton Gravels

Fenstanton Gravels. Click to expand.

The terrace gravels at Fenstanton Gravels are noted as having high fertility (as opposed to the other areas of naturally low fertility). Here the botanic evidence shows a presence of barley in addition to the grasses and clover which are also present at Connington. These higher fertility light soils can therefore be assumed to have been the initial focus of arable farming while the lower fertility light soils are more likely to have been used for pasture.

Alder woodland

During the Bronze Age period the valley base would have represented areas of wet, alder woodland. However, this only accounts for about 8% of the total area and the pollen evidence shows woodland covered up to 25% of the area during the Bronze Age.

Deciduous woodland

Other areas of deciduous woodland would likely have been present on the higher ground with lime rich soils.

A general decline in diversity of woodland from the River Great Ouse to Connington suggests one of these woodlands was present somewhere between River Great Ouse and Fen Stanton Gravels. Although we can’t be certain exactly where, this was most likely in the area shown on the map and would have persisted throughout the Roman and into the Saxon period but may have taken a ‘big hit’ in the Roman period.

The botany evidence includes fast grown ash which indicates this woodland was managed from the Bronze Age on.

Although we don’t have pollen or botany samples for other areas for the Bronze Age, it is likely that woodland was present at other high ground locations at this time. For example, the location of the present-day Brampton Woods and west of Bar Hill, but this and the extent of the woodland mapped here are largely speculation.

Open vegetation

The rest of the area would have been 'open'. This includes, scrub, grassland and areas of agriculture, both pasture and arable. But being able to identify where these different types of open land were is even more difficult.

The areas located on the gravel terraces, would have been natuarally open grassland due to a low water holding capacity. Those shown in yellow have a naturally low fertility while those shown in orange are naturally high fertility.

These are therefore also the most likely areas of early agriculture. The absence of Anthemis cotula (stinking chamomile) in the botany samples for this period suggests that farming had not yet extended onto the heavier soils of the higher ground (light green) although the data for this is limited.

The banks of the River Great Ouse

West of Ouse was a focus of Bronze Age activity and the botanic evidence from cremations in this area shows the immediate area around the cremations was wet with clover indicating pastureland nearby and Rumex indicating some grasses on sandy soils. Pollen analysis on samples from River Great Ouse (on the east bank of the river) identified large amounts of microcharcoal suggestive of woodland clearance and management. It is likely that agriculture was initially focused on the terrace gravels extending along the contact between these and the floodplain edge where wet, open ‘alder’ woodland was present.

Fenstanton Gravels

The terrace gravels at Fenstanton Gravels are noted as having high fertility (as opposed to the other areas of naturally low fertility). Here the botanic evidence shows a presence of barley in addition to the grasses and clover which are also present at Connington. These higher fertility light soils can therefore be assumed to have been the initial focus of arable farming while the lower fertility light soils are more likely to have been used for pasture.


The Iron Age

Open pasture, hedgerows, and crops expanding on to the floodplain.

Bar Hill

Bar Hill. Click to expand.

Although there may have been some woodland on the high ground to the west of Bar Hill in the Bronze Age period, we are confident it had been cleared by the Iron Age. There is no pollen or botany evidence for woodland and the botany evidence shows fuel included peat, coal twigs etc suggesting a shortage of wood for fuel.

Conington

Conington. Click to expand.

The area of open wetland wood was cleared or, more likely, a change in the hydrology increased flooding so there was a transition to sedge type vegetation by the end of the Iron Age. As the lower areas flooded they began silting up with alluvium. This is most apparent around Conington and Fenstanton Gravels while areas further upstream retained some alder woodland. The presence of henbane and other nitrogen fixers and weeds associated with clay rich soils, wetlands and pastoral activity all suggest that Iron Age farming was extending onto these new flood plain soils. Chenopods are present in the pollen record and could indicate brackish water, potentially from a tidal surge but more likely from ground water supplied by the underling geology of the Kellaways Sand, although high nitrogen levels could also account for their presence. The botany evidence from Conington also points to lots of hedgerows.

Fenstanton Gravels

Fenstanton Gravels. Click to expand.

Iron Age Fenstanton Gravels is like that of Roman Conington (see below) with sedges and juncus indicating a higher degree of wetland input, again this indicates that the area of wet alder had already converted to fen.

The banks of the River Great Ouse

The banks of the River Great Ouse. Click to expand.

There is limited botanic evidence for the River Great Ouse in the Iron Age period but this and the pollen shows a similar pattern to Fenstanton Gravels.

Brampton

Brampton. Click to expand.

Although the presence of woodland in the vicinity of Brampton Woods is speculation, for the Bronze Age there is clear evidence of a mature woodland near Brampton for the Iron Age.

Alconbury

Alconbury. Click to expand.

To the north of the high agricultural activity at Brampton, Alconbury is noted for the high diversity of grassland species in the pollen data (in contrast to Brampton West and West of Ouse which are all Lolium and Bromus grasses) suggesting this area remained relatively pristine in the Iron Age.

Bar Hill

Although there may have been some woodland on the high ground to the west of Bar Hill in the Bronze Age period, we are confident it had been cleared by the Iron Age. There is no pollen or botany evidence for woodland and the botany evidence shows fuel included peat, coal twigs etc suggesting a shortage of wood for fuel.

The whole area is dominated by clay rich, calcareous soils which can support woodland so the fact that it remains clear in the pollen record from the Iron Age is suggestive of animal grazing/pasture preventing any regrowth.

The presence of animals would have added to the nitrogen content of the soil. This area is therefore likely to have supported a heath type or scrubland vegetation as indicated by the pollen record.

Some charcoal of fruit, oak and hazel suggest the presence of hedgerows, perhaps indicating the initiation of some enclosures.

Floodplain and terrace gravels are present just to the east outside the study area and there is some suggestion that these areas are being exploited with the presence of brome grass, oat and sheep sorrel in samples from the settlement.

Conington

The area of open wetland wood was cleared or, more likely, a change in the hydrology increased flooding so there was a transition to sedge type vegetation by the end of the Iron Age. As the lower areas flooded they began silting up with alluvium. This is most apparent around Conington and Fenstanton Gravels while areas further upstream retained some alder woodland. The presence of henbane and other nitrogen fixers and weeds associated with clay rich soils, wetlands and pastoral activity all suggest that Iron Age farming was extending onto these new flood plain soils. Chenopods are present in the pollen record and could indicate brackish water, potentially from a tidal surge but more likely from ground water supplied by the underling geology of the Kellaways Sand, although high nitrogen levels could also account for their presence. The botany evidence from Conington also points to lots of hedgerows.

Fenstanton Gravels

Iron Age Fenstanton Gravels is like that of Roman Conington (see below) with sedges and juncus indicating a higher degree of wetland input, again this indicates that the area of wet alder had already converted to fen.

The largest habitat being exploited is that of nitrogen rich open grassland as indicated by goosefoot and clovers. The presence of elder and rubus in many samples is also indicative of the presence of hedgerows. The pollen evidence supports this interpretation of local disturbed grass land, and it is believed the whole fertile gravel area was grass meadow at this time.

The identification of vetch and buckwheat may indicate the use of green manures or that the area was also used for pasture. Evidence from insect remains also shows the presence of damp grazing ground in close proximity to the area excavated.

It is not clear from the palaeoenvironmental evidence what vegetation was present on the higher ground with lime rich clay soils but this may have been open pasture as indicated in other areas.

The banks of the River Great Ouse

There is limited botanic evidence for the River Great Ouse in the Iron Age period but this and the pollen shows a similar pattern to Fenstanton Gravels.

During the Iron Age period the floodplain in this area would have been an area of open slow flowing water as indicated by the pollen evidence. This became increasingly open in a natural climatically driven change from wet woodland decreasing in density to sedge fens.

As the landscape became more open it became increasingly available to cultivation. Dryland grass present on the terrace gravels would have given way to arable agriculture. Evidence of arable agriculture includes cannabis and rye in later periods. Rye prefers lighter soils such as those on the terrace gravels.

Lime woodland, more likely to be present on the till (higher ground) was also cleared to some degree giving way to slump or waste ground probably used for pasture.

Brampton

Although the presence of woodland in the vicinity of Brampton Woods is speculation, for the Bronze Age there is clear evidence of a mature woodland near Brampton for the Iron Age.

The pollen evidence shows a strong signal of woodland edge taxa, including bluebells, indicating a managed woodland with coppicing and managed rotation in very close proximity to the settlement. The woodland is therefore likely to have been larger in the Iron Age (and Roman) periods than it is today but heavily managed.

Indicators of high nitrogen environments, and clay rich soils in the botany data suggest the till was already being utilised for agriculture in the Iron Age period.

Pollen taxa fairy flax and botanic evidence of sheep sorrel show the light soils on the gravels were also being farmed.

Hedgerows are also first apparent in in this period, and in high quantity as indicated in the botany evidence.

Essentially, the palaeoenvironmental data show that all parts of the landscape around Brampton West were accessed during the Ion Age period except possibly the floodplain which is a greater distance to the settlement in this area.

A typical pattern of arable crops, comprising spelt on the clay rich soils, free threshing wheat on the free draining soils, and barley on both, immediately around the main settlement with pasture around this is therefore hypothesised. The presence of pulses suggests the floodplain was becoming increasingly fertile.

The one botany sample from Brampton South dating to the Iron Age indicates grassland was present locally on the terrace gravels and is supported by a pollen assemblage indicative of grazed grass land.

Alconbury

To the north of the high agricultural activity at Brampton, Alconbury is noted for the high diversity of grassland species in the pollen data (in contrast to Brampton West and West of Ouse which are all Lolium and Bromus grasses) suggesting this area remained relatively pristine in the Iron Age.

There is just a small amount of evidence for agriculture on the free draining soils of the terrace gravels, with mixed agriculture elsewhere.


The Roman period

Extensive farming: The landscape is more heavily managed with ditches as well as hedgerows to demarcate land and a shift to arable farming on heavier soils.

Bar Hill

Bar Hill. Click to expand.

There is evidence of increased land enclosure with ditches used in addition or as an alternative to hedges in the Roman period. This is shown in the palaeoenvironmental records as a slight increase of damp/wetland indicators such as sedges, nettles and dock and may also demonstrate that agriculture was expanding into the floodplain.

Conington

Conington. Click to expand.

The Conington assemblage indicates agriculture expanded from the light soils on the gravels onto the floodplain and possibly onto the till margins, evidenced by a shift in weeds to clay soil types (the inclusion of Anthemis cotula for example).

Fenstanton Gravels

Fenstanton Gravels. Click to expand.

Arable farming is evident from hare’s ear and cannabis while pollen from other plants such as foxgloves suggests the presence of land enclosures in the form of hedgerows probably dating to the Roman period. The pollen evidence show rye is only present between Fenstanton Gravels and River Great Ouse.

River Great Ouse

River Great Ouse. Click to expand.

The pollen evidence shows a large grassland environment probably covering the terrace gravels but also extending onto the floodplain at this time.

Brampton West

Brampton West. Click to expand.

The pollen signal from alder carr is gone by the Roman period suggesting that even the most upstream areas of the River Great Ouse floodplain are now sedge dominated.

Alconbury

Alconbury. Click to expand.

This area remains largely unchanged from the Iron Age period and comprises open scrubland rather than woods on the dry ground, although there is a small pollen signal of oak and sorbus this is likely to come from Brampton Woods.

Bar Hill

There is evidence of increased land enclosure with ditches used in addition or as an alternative to hedges in the Roman period. This is shown in the palaeoenvironmental records as a slight increase of damp/wetland indicators such as sedges, nettles and dock and may also demonstrate that agriculture was expanding into the floodplain.

The charcoal assemblage is also more varied than for the Iron Age period but with oak noticeably absent. It can therefore be reasonably assumed that this area remained cleared of any woodland in the Roman period.

Conington

The Conington assemblage indicates agriculture expanded from the light soils on the gravels onto the floodplain and possibly onto the till margins, evidenced by a shift in weeds to clay soil types (the inclusion of Anthemis cotula for example).

This may reflect extensive farming practices (where larger areas are given over to agriculture) rather than intensive farming. There is also an increase in spelt during the Roman period which is known to be tolerant of clay rich soils.

Weed species are split between species specifically indicative of either free draining or wet soils. This could show that land is being increasingly managed, either by drainage or deliberate flooding of areas to improve fertility.

Plant species indicative of high nitrogen environments decrease to the south of the Conington Landscape Block suggesting the higher ground was still less intensively farmed, probably as open pasture.

Fenstanton Gravels

Arable farming is evident from hare’s ear and cannabis while pollen from other plants such as foxgloves suggests the presence of land enclosures in the form of hedgerows probably dating to the Roman period. The pollen evidence show rye is only present between Fenstanton Gravels and River Great Ouse.

A huge increase of agricultural activity onto the high ground to the south dominated by calcareous clay rich soils is evident from the botany data, with an increase in the presence of corncockle and sheep sorrel, as is an expansion onto the gravels.

The wetland area (identified when using the Strahler order function in GIS to map river channels from the ground elevation) is still present, and arable agriculture including rye and spelt seems to be focused around this feature, both on the till and gravels. The area within 200m of the settlements occupied during this period would have been heavily disturbed.

There is also evidence of pastoral activity which is therefore likely to have been on the higher open ground.

River Great Ouse

The pollen evidence shows a large grassland environment probably covering the terrace gravels but also extending onto the floodplain at this time.

Arable agriculture is indicated by oat, wheat and corn salad. It is likely that the area used for agriculture extended along the boundary between the lighter soils of the terrace gravels and the more fertile floodplain soils.

Lots of Anthemis cotula shows clay rich soils were also being utilised.

The higher ground is likely to have remained open woodland at this time, as evidenced by fern spores. The till is therefore interpreted as being the focus of open pastureland but with with increasing levels of management.

Generally, the impression given moving from the river channel edge is agriculture on the floodplain margin then pastoral ground with woodland persisting on the highest ground.

To the west of the River Great Ouse there is little change from the Bronze Age to Saxon periods with dry deciduous wood on the high ground and wet woody vegetation decreases but still indicated on the floodplain.

The botany data of Anthemis cotula and evidence for hedgerows suggests some fields are present on the clay rich soils of the floodplain.

Brampton West

The pollen signal from alder carr is gone by the Roman period suggesting that even the most upstream areas of the River Great Ouse floodplain are now sedge dominated.

There is generally little change in the vegetation to the west of the area, but large changes are apparent in the vegetation to the east with increased microcharcoal, vetches and mallow suggestive of manuring in an attempt to increase soil fertility from the pollen data.

This is supported by the botany data which shows a big increase in sheep sorrel, chick weed and other species which prefer free draining soils. There is also suggestion of a smaller scale expansion onto the till and hemlock and nettles indicating increased disturbance around the settlement.

Alconbury

This area remains largely unchanged from the Iron Age period and comprises open scrubland rather than woods on the dry ground, although there is a small pollen signal of oak and sorbus this is likely to come from Brampton Woods.

Lots of grassland is present in this area with very little sedge suggestive of light grazing.

There is no evidence of agriculture moving onto the till in the botany data. Diversity of the vegetation remains high with open scrub and wetland species still present suggesting this area is more peripheral to agricultural activity.

A small amount of arable activity may have been present on the terrace gravels as evidenced by corn salad in botany samples from the settlement.

The Anglo Saxon period

A switch to intensive farming or population collapse?

Anglo Saxon Period

We only have enough data to discuss Brampton West for the Saxon period as this is where the human activity retracts to in this period. There is evidence of a wetland area at the centre of Brampton West which also represents a strategic position at the confluence of two rivers with access to multi-tonal resources.

It is unclear if the reduction in settlement area also represents a decrease in population size but the botanic evidence shows that the farming at Brampton West continued to be intensive with nitrogen enrichment of soils. This evidenced by a high quantity of vetch and a big jump in fossils of pulses.

A large increase in Anthemis cotula demonstrates agriculture extending onto the till at the expense of the woodland which may have retracted to it’s present-day size at this time. The diversity of the woodland taxa also decreases in the pollen record during the Saxon period suggesting the woodland edge is further away from the settlement.

The absence of grasses in the pollen data with an increase in docks and cereal suggests the whole of the natural environment for this habitat on the terrace gravels was now given over to agriculture but some wetland taxa do persist.

Although settlement appears to have centralised at Brampton West there is some evidence of agriculture persisting on the clay and nitrogen rich floodplain soils at Conington. The oak charcoal at Conington is of young, small and medium wood possibly indicating some woodland regeneration in the Saxon period, but this data is very limited.

Concluding statement/ limitations: all models are wrong but some are useful 

We hope this StoryMap has presented the wider vegetation setting of the archaeology uncovered during the A14 excavations in an accessible way.

While we can be fairly confident that this landscape remained largely open throughout later prehistory and into modern times, this is just a first tentative step towards reconstructing what the vegetation across the landscape would have been like.

This approach has allowed modelling of changes in floodplain vegetation and mature woodland sand an estimate of agricultural activity based on weed ecology.

Next Step

We will test the model by undertaking statistical testing (using a Multiple Senario Approach) on a case study of the data-rich Brampton West area. It is hoped this process provides valuable lessons for future large-scale infrastructure projects.

Discover more

Although the A14 field work has now finished the post excavation and publication work are ongoing. As new documents are finishe they will be made publically available  here .

This vegetaion model takes us up to the Anglo Saxon period, to see how the vegetation continued in this area see the work of Jason Peters  here .

Acknowledgements

Date sources:

Grant M (2021) A14 Environmental Specialist Report: Pollen Analysis [Unpublished Report] MOLA Headland Infrastructure

Allison E (2021) A14 Cambridge and Huntingdon, Cambridgeshire: Insect remains from TEA5, TEA7, TEA10, TEA14, TEA20 and TEA29, Canterbury Archaeological Trust

Bunting J (2022) A14 pollen data: initial REVEALS analysis to assess past landcover – initial notes

MOLA Headland Infrastructure (2019) A14 Cambridge to Huntingdon Improvement Scheme, Archaeological Investigations Volume 3.6: Geoarchaeology Assessment

Taylor D, forthcoming, A14 Cambridge to Huntingdon, Geoarchaeological Deposit Modelling

Wallace M, Aitken E, Gonzalez Carretero L, Roberts K, Fosberry R, Hunter K, Wyles S, Bailey L, and Turner, K, forthcoming, A14 Archaeobotany Analysis Report x8

West E, Scholma Mason O, Pullen S, Christie C, Atkins R, White J, forthcoming, A14 Landscape Block Reports x8

Map sources:

Biome map

Ville Koistinen (user Vzb83), CC BY-SA 3.0 , via Wikimedia Commons

Britice map

The University of Sheffield copyright and database rights reserved 2018

Geology maps

Contains British Geological Survey materials ©UKRI 2024

Lidar

© Environment Agency copyright and/or database right 2020 All rights reserved

Rivers

© Environment Agency copyright and/or database right. © Crown copyright and database rights 2024 Ordnance Survey 100024198 and © Crown copyright and database right 2024 OS 100030994

Soils

Cranfield Soil and AgriFood Institute (CSAI), supported by Defra:  https://www.landis.org.uk/soilscap es/ 

Post glacial landscape video

Virtual Soil Science Learning Resources:  https://www.youtube.com/watch? v=2QhlVuF9xQg 

Bunting J (2022) A14 pollen data: initial REVEALS analysis to assess past landcover – initial notes