Worcestershire Record No. 25 November 2008 pp. 21-23
Wendy Johnson
The purpose of this paper is to report our experiences and to make a plea for a standardised method for coppice re-growth surveys carried out in Worcestershire Wildlife Trust (WWT) woodlands. First and foremost the method must be practicable as access to the site becomes more difficult. It needs to be simple enough to be carried out by any volunteers; the results being reproducible and comparable whoever collects the data. It should have a clear purpose and be simple enough to be carried out right through the coppice cycle. I have been involved in surveys of coppice re-growth in Grafton Wood for nine years and our experiences in carrying out these surveys should inform any method used by WWT and perhaps other organisations in the future.
I have never felt entirely satisfied with any of the methods of survey used and they have really been made it up as we went along. Despite enquires to the Forestry Commission and the Woodland Trust, as well as the Wildlife Trusts, plus research in books and on the internet I was not able to find a ‘standard’ method for studying coppice re-growth. Recent searches of the internet still found very little about surveying or monitoring coppice re-growth although there is more about the affects of muntjac on coppice re-growth and quite a lot on coppicing and its value for woodland crafts and bio-fuel.
The coupe where the first survey plot is situated was coppiced in late 1998 and measurements of growth have been made every winter (late December or January) since then. Thus there is a continuous record from 1999 to 2007. A second survey of a much larger area, selected specifically to look at the effects of animal damage on re-growth in a coupe coppiced in 2003, was also undertaken – the first measurements being carried out in February 2004 after one years growth.
The methods used are summarised below with comments on the many practical problems encountered and with suggestions for adaptations and improvements to these.
The original survey method was based on one that had been used some years earlier in another woodland. This method became both too time consuming and impractical as the stools got big and brambles re-grew. It involved setting out a 10m square using a compass and tape. All the coppice stools (18 in all) within the square were given numbers and their locations plotted on a plan by measuring co-ordinates from the SW corner. Problems began straight away:
| What exactly is a coppice stool? |
| Should it be a certain minimum diameter? |
| Should a single stump be included? |
| Is this large irregular stool really two? |
| What species is it? Identifying the species when they have just been coppiced is difficult |
Using the inherited survey scheme the plan was to count the number of shoots for each stool and to measure the length and diameter at the base of the longest and shortest shoot. In the early stages this may give an estimate of the volume of wood produced. Any animal damage was also noted. For the first two years access was quite easy, the stools easily found although some tags (small numbered squares of wood or metal attached to the stools with wire) were lost, and the new shoots could be measured without difficulty.
However every year more problems became evident:
| Access became more and more difficult due to bramble growth which became eye, if not life, threatening! |
| Tags marking the coppice stools were lost or very difficult to locate. They need to be securely fixed to a shoot as high up as possible in the first years (and moved up as the shoots grow). They need be brightly coloured or be attached with e.g. red PVC covered wire from electric cable. |
| Numbers on the tags faded. They should be permanent e.g. stamped on metal with a metal punch. |
| Stakes marking the corners of the plot should be substantial (e.g. 40 – 50 mm diameter), well driven in, tall enough to be seen when the vegetation grows and have some eye catching colour on them. Garden canes were used originally and they were knocked over by the deer. Also they did not stand out which at the time was thought an advantage for fear of human interference. |
| Counting the number of shoots became difficult once they started to branch. Most stools had between 10 and 20 original shoots but up to 31 were recorded so once they branch and branch again the problems can be imagined. Thus only the original shoots from the base were counted and some of these die off as others become dominant. |
| Measuring the basal diameter became somewhat imprecise as moss and debris collect over the stool. |
| After a few years the shoots became too tall to measure – over 4metres in some cases. |
Photographs were also taken across the plot from all four corners but after about three years it became impossible to see beyond the first few shrubs.
This plot is now due for re-coppicing.
The shortcomings of the method became clear and we started to question its value, purpose and practicability. It also became clear that re-growth was being reduced by something eating the shoots. Very few rabbits had been seen in Grafton Wood and there were no droppings in the survey plot area. On the other hand deer and deer footprints were seen and muntjac were often heard. Since most of the nibbling occurred on the ends of shoots up to 1m or more above ground it was concluded that deer must be responsible rather than rabbits. It had been clear for some time that deer were a problem in other parts of the wood and that a survey was needed where deer were excluded.
Within a newly coppiced coupe a large more or less rectangular enclosure to exclude deer was set up using plastic fencing. Within this 76 stools were identified and around the outside another 76 were randomly selected. They were all identified by stakes (from the coppicing) driven into the ground next to the stools. Metal tags with numbers stamped on were attached to the top of the stakes. With such a large number of stools it was clear that the original survey method would not be suitable. Also the main purpose of this survey was to investigate the impact of animal browsing on re-growth. So a much simpler method was devised which gave some comparative measure of coppice re-growth and the impact of animal damage. Each winter the maximum height and spread of the growth on every stool was measured and the amount of damage was recorded in one of three categories:
Just three categories were chosen, rather than percentage damage, as allotting stools to the appropriate damage category was reliable with no disagreement between assessors. Past experience in vegetation surveys with the use of percentages has shown that different assessors may differ by as much as 20%. Some would argue that there should be an even number of categories so there is no ‘sitting on the fence’ in the middle but in this particular survey most stools fell into categories 1 and 3.
Further problems included:
| After a few years some of the stakes rotted and others outside the enclosure were pushed over by the deer. |
| On returning after a year it was not always clear which stool the stake related to (although the stakes were slightly easier to find than the tags attached to the branches used on the first survey plot). |
Here again after five years the survey sites both inside and outside the enclosure became almost inaccessible due to bramble growth. Cutting a way through the brambles to the stools will also allow easier access for the deer! It is clear that deer browsing has a marked affect on coppice re-growth but that most hazel and birch do recover and make good growth although those outside the enclosure remain a year or two behind the stools inside. Aspen does not produce true coppice stools after cutting but grows a thicket of single shoots from the roots adding to the access difficulties. It is not affected by browsing presumably because it is bitter and not liked by deer or rabbits. The species which suffered most was field maple which produced many shoots after cutting, almost all of which are eaten right down. Some field maple stools and stumps died and others struggled with one shoot reaching a meter or so after five years – probably as they became protected by bramble. It is suggested that all field maple stools and stumps are individually protected with brash after they are coppiced. As the purpose of the second survey was the effect of deer browsing this was concluded after five years – a report was published in the Worcestershire Record No 18 April 2005. After devising the simpler method it was possible to use this on the original site and to convert the earlier measurements to conform to this. The raw data collected from both sites, with analysis and observations, have been sent to WWT every year.
Neither method actually measures the volume of wood produced – the original method had enabled a very rough estimate in the early stages, until the shoots branched, based on number and size of shoots. However for comparison purposes it is not necessary to know the amount of timber produced as conservation management is not concerned in maximising production.
A third even simpler and quicker survey method to assess damage and growth, along a single line transect across a coupe, is now being tried in Grafton Wood. A report on this in relation to deer and/or rabbit damage and fencing will follow.
However, if coppice re-growth surveys are to continue in WWT woodlands, what we do need to arrive at is a simple, quick standardised survey method which can be carried out easily over the whole coppice cycle and which can be applied by new volunteers. The reasons for carrying out the surveys should be clearly defined and consideration should be given to how the results will be analysed. This would then provide data for comparison of different coupes within woods and between woods. It would also be valuable to continue the surveys over a number of coppice cycles to assess the impact of coppice management over time.
References
| http://initiatives.smallwoods.org.uk/index.php |
| http://www.greenwoodcentre.org.uk |
| http://www.forestry.gov.uk/research |
| COOKE AS & LAKHANI KH, Damage to coppice re-growth by muntjac deer Muntiacus reevesi and protection with electric fencing. English Nature, Northminster House, Peterborough PE1 1UA, UK, Institute of Terrestrial Ecology, Monks Wood, Abbots Ripton, Cambridgeshire PE17 2LS, UK. Received 27 February 1995; accepted 15 May 1995. ; Available online 30 November 1999. |
| JOHNSON C, JOHNSON W & TILT J. 2005. The Grafton Wood animal
damage survey Worcestershire Record No 18 April 2005 pages 29-31. |
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