Woodlands since the last Ice Age Part 1 .

We have had several Ice Ages but the last one was about 20,000 years ago, which in geological terms is nothing. In between each ice age plants and animals would have recolonised and as a result we have fossils which show that woodland did exist in these inter glacial periods. For example  Silver fir has been found in Cromer forest beds along with Water Chestnut.

Weather forecast; January 18th, 17,999 BC.  The recent cold spell is possibly nearing its end and a warmer weather pattern is expected to push in from southern Europe. Flood warnings have been issued and low lying areas  between Norfolk, Suffolk,and Lincolnshire across to Holland and Belgium, are particularly vulnerable. An amber warning has been issued for this region. This belt of warmer weather will gradually push northwards. It is possible that some sheltered spots in the Midlands and Northern England will be completely ice free by the end of the millennium.  However Scotland will remain in the grip of arctic conditions for some considerable period, recolonisation of this area is not advised for at least 2,000 years.

Seriously, the exact date is not known and if you reference different authorities you will get different estimates. I like Oliver Rackham as someone who was pretty clued up…. He says.  ‘Woodland history began 12,000 years ago, when the climate became possible for tree growth. Trees and woodland plants returned by wind and bird borne seed from their southern  refugia to form a series of wild-wood plant communities. There followed a long epoch of relative stability, the Atlantic period (6200 – 3800BC )  with a climate not very different from that of the mid-twentieth century. ‘

It was of course during this period that the amber warning for floods came true and we separated from mainland Europe. Was this BREXIT number 1?Europe map end of ice age

Let us not get too hung up with the dates and lets look more at the sequence of events. There are several areas of evidence which can direct us to a fairly good understanding of what happened as a result of the January 18th weather forecast.

If today you were to travel to northern  Siberia or Canada, to the very edge of the ice cap and observe what the vegetation looks like then that would most likely be what the vegetation was like in southern England at the end of the last ice age. Then if you were to walk in a southerly direction down through Siberia or through Canada you would see the same changes in vegetation as if you had stood still in southern England for several thousand years and watched and recorded the changes in vegetation as it gradually warmed up. Obviously the first option is more practical and what you would see is the growth of mosses and lichens mixed with small grasses, heathers, crowberries  and maybe a low growing bush called creeping willow i.e a Tundra Habitat. This region does not support trees and is where the soil is frozen beneath the surface ( permafrost ). It only warms up above zero for a few months each year during the summer and even then below a depth of about 50cm it is still frozen.

Eventually trees will be seen as you walk steadily south and these will most likely be Silver birch, Poplar and Willow. This is the zone (biome) known as Taiga which extends  all the way round the northern hemisphere through Canada, Alaska, Siberia and northern Scandinavia. The species are fairly similar across the entire region as there is still a connection (sort of) between Alaska and Siberia.  Mile by mile as you progress further south conifers will appear and the forests will become more dense. Taiga is the world’s largest land biome, making up 29% of the world’s forest cover. Several years back we travelled from Moscow to Beijing on the Trans Siberian railway. We stopped off a couple of times, once near Lake Baikal for 5 days and once in Mongolia, for 10 days. The journey from Moscow to Lake Baikal took 5 days and it was largely through woodland, miles and miles of it, days and days of Pine and Silver birch – it certainly brought home to you the vastness of this region.

This slideshow requires JavaScript.

Gradually the coniferous trees will decline and new deciduous trees will make an appearance, species like Oak and Beech, one tree that you will not see much of o your journey south from the ice cap will be Elm, because of Dutch Elm but we have evidence that this was one of the early colonisers after the domination of Pines.

Of course this evidence from what is here today does not take into account the influence of man, but I will come on to that soon. However next I want to talk about pollen analysis, as this is the second major piece of evidence that can shed light onto the development of woodlands since the last ice age.

I will briefly explain pollen analysis,but I will write a more expansive account of it shortly as I think it is quite fascinating. Pollen analysis explained in more detail.

Pollen grainsThere are two features of pollen which combine to make its analysis a useful tool. Firstly the outer coat of pollen grains is made of a silica like material which is extremely resilient and can survive thousands of years. Secondly this outer coat is quite distinctively marked and can be used to identify the species it has come from, in most cases.  So by taking core samples of peat from a peat bogs you can separate them into layers and the deeper layers will obviously be the oldest and contain pollen from the plants that were about at that time. So you can get a picture of what trees and other plants lived thousands of years ago and then through to the present. The patterns seen from this analysis are largely similar to the species encountered on a walk in a southerly direction from the ice cap.   There are various problems and considerations to be taken into account with pollen analysis and I will look into these in my more detailed account latter on. Also it can now be linked with carbon dating to get a better idea of timescale. Below is a graphical representation of the pollen analysis from Hockham Mere in Norfolk this was the first one to be carried out. It shows the amounts of pollen for the major species on a vertical time scale. the base of the graph represents about 12,000 years ago, the top is the present

Data from Bennett (1983)..

.

If you can read the small print, then the first coloniser is Betula (Silver Birch) followed by Pinus (Pine) then we have Ulmus (Elm) quickly followed by Quercus ( Oak) and so on.

OK lets finish off with a brief outline of man’s effect on woodland in the prehistoric times………  More on recent history ( post birth of Christ) in part 2.

As it was warming up man was no doubt keeping pace with the colonisation of the plants. However in the early years after the end of the last ice age, man was a hunter gatherer and as such would have had a minimal effect on the woodlands. His population was quite small anyway and he was not farming so there would only have been a small amount of tree felling. This to provide material for the construction of shelters and also for fire wood.  Man first colonised hill top sites, because here the trees would have been smaller and more easy to cut down with primitive tools. Also hill tops would offer a more secure position with regards to warding off other tribes and wild animals.. Early man may also have cleared small patches in the woodland to encourage the natural colonisation of plants which provided food like brambles  providing blackberries. But no arable farming as such.

Gradually man became less hunter and more farmer, around 500 BC. This now had a much more dramatic effect on woodlands. Farming hill tops was not that clever…thin soils and windy, cold conditions. So man shifted his activities down into the valleys, here he cleared much bigger areas to make little villages and more substantial houses and of course fields to grow crops in and for animals which had been domesticated. The abandoned hill top sites were still used but largely  for sheep grazing so they developed into moorland, heath and downs, not to recover into woodlands.  A few areas have recently developed into secondary woodland with the reduction in rabbit population but that’s another story.

So by the time of the Roman invasion, English countryside had lost 50% of its woodland and would have looked somewhat like it looks today….no motorways, telephone wires, national grid, but fields and woods with little villages.

%d bloggers like this:
search previous next tag category expand menu location phone mail time cart zoom edit close