Monitoring deer damage at Grafton Wood
John Tilt
Grafton Wood is a 56 hectare ancient woodland purchased by Worcestershire Wildlife Trust and Butterfly Conservation in 1997. A management plan drawn up shortly after acquisition required 12 hectares of coppice in the centre of the wood (Fig. 1.). This was to be cut at one hectare per year on a 12 year rotation. We are now in year two of the second cycle - 14 years of coppicing.
From an early stage coppice stools showed considerable damage caused by animal browsing. As a result several methods to protect the stools were tried and a method of monitoring the damage was developed. This paper describes the development of both fencing methods, deer control, and monitoring methods.
Protection:
We are now fencing a section of each coppice plot with a 150 metre circle of metal thin gauge netting five feet high. This encloses 1800 square metres of coppice, 36% of each plot.
It was found that deer preferred browsing ash and field maple, so in addition large ash stools are fenced separately and smaller stools covered with coppiced brash. Both fencing and protection must be carried out immediately after the coppicing operation.
Deer Culling:
In winter the deer are culled by a deer control organisation called the Deer Initiative. The cull takes place two days per month until a pre-set target number of deer is reached. Both Muntjac and Roe Deer are shot and the wood is closed to visitors during the cull. The decision to cull is reviewed each year after reviewing the monitoring results.
Monitoring
Method of Animal Damage monitoring in coppice plots.
Each coppice plot is surveyed each autumn for three years after cutting.
In each plot a transect is walked along a straight line diagonally through the plot in such a way that the line passes through the animal exclusion enclosure.
The transect is between 70 and 100 metres long and one metre wide. The ends of the transect are marked on trees at the start and end of the line, so that the same route can be repeated.
Recording:
While walking the transect, the following information is recorded for each coppice stool or tree stump encountered.
Species.
Maximum re-growth height (metres).
Stump or Stool?
% of twigs damaged on each stump or stool.
Is the stool of stump inside or outside the enclosure?
Comments.
For each coppice coupe the following information is recorded:
Coupe Number.
Date of cutting.
Type, height and length of enclosure fence.
Length of transect.
The data will then be keyed into a spread sheet and analysed using the Excel pivot table to give the attached information (see table 1).
A map is also prepared to show coppice numbers and dates of cutting. The results of the survey are presented at the spring Grafton Wood Management Committee meeting and decisions made about future actions regarding enclosure fences (type and length) and the amount of deer culling. (Note. Proposals for culling are always considered by Worcestershire Wildlife Trust and Butterfly Conservation and have to be approved or not before action).
Development of the System
During the 13 years we have been coppicing and observing deer damage we have tried various ways of solving this problem.
Fencing
In 2002 we experimented with plastic deer fencing a 25mx25m square in Section named 4S. A method of measuring the effectiveness of this was developed by Cyril and Wendy Johnson which measured the volume of regrowth inside and outside the plot. The growth inside the plot was almost double that of the unprotected area. However in was observed that the plastic fence could be penetrated so some damage inside the plot was recorded. This survey was continued for some years and it showed that regeneration was satisfactory inside and after a number of years also outside the fence. However, observation showed that the area behind the fencing away from the ride was extremely heavily grazed - the deer were using the fencing and good re-growth within the fenced area as cover. (Johnson et al., 2005; Johnson, 2008 and Tilt 2008).
The plastic fencing method was continued until 2006 (plots 9N, 9S) when the Forestry Commission became involved. Their staff considered the problem to be aggravated by rabbit grazing and as rabbits were able to penetrate the plastic fence we should use metal mesh fencing. They suggested the use of three foot high metal wire netting fencing rather than the plastic.
So sections 13, 9S, 9N, 10S, 10N were fenced with three foot metal fencing. In section 8N five foot high plastic fence was used.
Using the new transect monitoring method of simply measuring % damage and height of re-growth on stools and stumps the new metal fencing method was tested and compared with the five foot plastic fencing. Table 1 shows the results.
Grafton Wood Deer Damage | 10/09/2007 | |||
| Fence | Wire | |||
| Years | (All) | |||
| Plot | N13 | |||
| Enclose | ||||
| Species | Data | Inside | Outside | Grand Total |
| Ash | Average of Height | 1.05 | 0.60 | 0.90 |
| Average of Damage | 50.00 | 100.00 | 66.67 | |
| Count of Species | 2.00 | 1.00 | 3.00 | |
| Hawthorn | Average of Height | 0.60 | 0.25 | 0.32 |
| Average of Damage | 20.00 | 97.50 | 82.00 | |
| Count of Species | 1.00 | 4.00 | 5.00 | |
| Hazel | Average of Height | 1.60 | 1.11 | 1.16 |
| Average of Damage | 100.00 | 22.14 | 31.88 | |
| Count of Species | 2.00 | 16.00 | 18.00 | |
| Oak | Average of Height | 0.15 | 0.05 | 0.10 |
| Average of Damage | 100.00 | 0.00 | 50.00 | |
| Count of Species | 2.00 | 2.00 | 4.00 | |
Total Average of Height | 0.81 | 0.69 | 0.71 | |
Total Average of Damage | 74.29 | 55.56 | 59.41 | |
Total Count of Species | 8.00 | 30.00 | 38.00 | |
| Fence | Plastic | |||
| Years | (All) | |||
| Plot | N8 | |||
| Enclose | ||||
| Species | Data | Inside | Outside | Grand Total |
| Birch | Average of Height | 1.43 | 1.00 | 1.33 |
| Average of Damage | 0.00 | 0.00 | 0.00 | |
| Count of Species | 3.00 | 1.00 | 4.00 | |
| Hawthorn | Average of Height | 1.07 | 0.97 | 1.02 |
| Average of Damage | 0.00 | 66.67 | 33.33 | |
| Count of Species | 3.00 | 3.00 | 6.00 | |
| Hazel | Average of Height | 1.57 | 1.49 | 1.51 |
| Average of Damage | 0.00 | 0.00 | 0.00 | |
| Count of Species | 3.00 | 11.00 | 14.00 | |
| Oak | Average of Height | 3.00 | 3.00 | |
| Average of Damage | 0.00 | 0.00 | ||
| Count of Species | 1.00 | 1.00 | ||
| Salix | Average of Height | 2.23 | 2.23 | |
| Average of Damage | 0.00 | 0.00 | ||
| Count of Species | 7.00 | 7.00 | ||
Total Average of Height | 1.81 | 1.33 | 1.57 | |
Total Average of Damage | 0.00 | 17.65 | 8.82 | |
Total Count of Species | 17.00 | 17.00 | 34.00 | |
Table 1. Results recorded by transect monitoring of stump and stool re-growth inside and outside areas fenced with wire netting and plastic netting fences.
The results show the plastic mesh fencing to be 100% successful and that the three foot metal fenced areas showed 74% Damage. In fact the damage inside the enclosure was higher that the unprotected areas. Section 9S adjacent to the main entrance and on the public right-of-way showed no damage inside the three foot fence probably because deer were disturbed so preventing browsing. However analysis of all the coupes using three foot fencing showed slightly better regeneration inside the enclosure: 39.13% Damage and height of 1.15m inside and 52.09% damage and 0.95m regrowth outside. As the deer tend to browse on the edge of the plot this was not significant.
After 2008 a five foot metal fence was used on section11 and the diameter of the enclosure was increased to 48 metres. Using the transect method the re-growth was monitored. In December 2008 deer culling also started.
Analysis of the data shows that the damage inside the five foot enclosures is negligible apart from coupe 12 where the fencing was not installed until the autumn after the coppice had been cut. (The delay was caused by waiting for grants).
In 2010/11 the second cycle of the coppice began with stools being cut 12 years after the initial coppicing. The effect of wire netting fencing on re-growth was remarkable. Deer damage inside the enclosures was zero and outside 33% but the overall regrowth height was 1.6m. Brashing larger stools was also shown to be effective in preventing deer damage.
Tree Species
Analysis of all the years shows that deer have definite preferences for browsing certain tree species.
Ash and Field Maple are by far the most popular – followed by Hawthorn, Oak, Birch.
Hazel and Willow was not heavily browsed and Aspen was left untouched.
It was found that only Ash could be killed by continuous browsing, regeneration on other species was slowed down but usually succeeded by the third year after coppicing.
Discussion
Why not fence the whole plot? Providing stools are not killed, a slowing down of regrowth can extend the ground flora stage of the coppice cycle which has a positive effect on insects and in turn on the insect predators. In addition to that I am quite sure that with no easily available food that deer would penetrate the five foot fencing.
It can be seen from the above that a simple and easy to understand monitoring system is necessary to measure the effects of the different forms of management. The existing system has the disadvantage that each stool is recorded as equal taking no account of its size, whereas the system developed by the Johnsons did take that into account. However the newer method does measure a transect band through all coppice coupes both inside and outside enclosures. It is quick and easy to do and can be done for three years after which time the coupes are difficult to penetrate. The system is the way to communicate the situation to the policy makers if they are willing to look carefully at the tables of results provided.
Fencing method.
This was developed over a number of years using a circle rather that a square is the cheapest way to enclose the maximum area. The plastic fencing was easier to erect but has now become far more expensive. The metal fencing has a major disadvantage in that it difficult to remove after about four years when it is not required. Metal fencing left on the coppice plot will be extremely dangerous for subsequent chainsaw users on the next coppice cycle and must be removed.
Deer numbers
The number of deer in Grafton Wood has decreased significantly since culling started in 2008. From the regeneration survey and looking for deer tracks it can be seen that there is still a small population of deer there. At the last culling session no deer were shot which is the best indication that the numbers are down.
Conclusion
A simple monitoring system is necessary and all coppiced coupes should be monitored.
Use the monitoring system to measure the effects of different management techniques.
Some fencing is necessary and metal netting circles seems to be best (despite the difficulty of removal).
Deer culling is effective providing the wood can be closed off from visitors on culling days.
References
Johnson, C., Johnson, W. & Tilt, J. 2005. The Grafton Wood animal damage survey. Worcestershire Record, 18:29-31.
Johnson, W. 2008. Coppice survey – some experiences from Grafton Wood. Worcestershire Record. 25:21-23.
Tilt, J. 2008. Practical notes on the Grafton Wood deer damage survey and a new quick method. Worcestershire Record. 25:23-24.
Images
Fig. 1. Grafton Wood coppice rotation map and plot names. ©John Tilt
