Kinver Edge Summer Woodland Survey

Introduction

Despite it being “that wet Thursday” which will be known as the storm of 2012 in years to come, volunteers on the summer working holiday at Kinver Edge took a day to survey selected parts of the woodland. The data contributes towards the point centred quarter technique which can be used to give densities of trees, and conversely the average area occupied by an individual tree.

Whilst measuring distances of trees from randomly selected points, volunteers also recorded the species and the DBH (diameter at breast height): allowing analysis of what trees make up the sample areas, and also – based on relative size – the age distribution.

The resulting numbers can be input to produce a series of graphs and charts which then need further interpretation.

Flaws

There are a number of flaws which must be considered, for both the recording and interpretation.

• Tree identification skills: misidentification of trees will affect the results of species based analysis.
• Randomness of sample points: although points were selected at random, samplers may choose to avoid the tallest dampest vegetation on a particularly miserable day, and instead select a more favourable location. 
• Size: although it may be possible to record the more obvious new growth and saplings, it is highly probable that many of the youngest trees are overlooked. They could be low enough to be hidden by vegetation, or appear as field layer annuals.

Sample areas

Two areas were chosen based on a subjective view of the differences in species composition, and geographically distant. Effectively, these were a representation of the north and south landscapes. In each area, four sample plots were recorded: the northern area plots were bound by paths, allowing results to be tied to measurably sized plots; the southern section was not, and was truly plotless.

For an idea of how representative the sample areas are in relation to the overall size, using the National Trust’s GIS mapping system, the wooded area of Kinver Edge is around 91 hectares. The total sample plot size of the northern sample plots is around 1.7ha; so around 1.9%

Individual plot analysis

The following are a few of the more interesting results:

i)                    Oak plantation.

Plot number 5 in the south of the site has been managed for several years with the intention of producing a crop of oak in the future. The species composition may only appear 36% oak, but the distribution of DBH shows that the majority of the remaining 64% are less than 5cm. Evidence on the ground shows this to be coppice re-growth, including re-growth of oak. The larger oaks in the 50-54.9cm and 85-89.9cm range are likely to be a known line of historic oaks close to the sample area, which do not reflect the nature of the plot.

ii)                  Oak dominant.

Sample 2 lies in the northern section of the site. The plot is dominated by oak, with rowan forming the second most recorded species. Using the data for DBH analysis, shows oak and rowan forming the understorey to an oak dominated canopy.

Large plot results.

Compiling the eight sets of data into two sets based on northern and southern areas increases the overall sample area date size:

i)                    Northern sector.

Based upon 168 records.

Species contribution:

So oak is dominant, which is not necessarily a surprise. Maybe rowan being the next most common species is more of a surprise. It is known from evidence on the ground that aspen is present in the north of the site and due to the suckering nature of the tree has come to dominate a particular area: yet it isn’t recorded here. We could consider it’s presence as localised, whilst what was recorded is a more general picture.

DBH distribution:

Plotting the results of just the three main species (oak 44%; rowan 14%; birch 13%), so as to avoid the graph becoming too messy.

Tree density:

Based on the 168 records, it is calculated that there are 637 trees per hectare, each tree occupying a space of 15.7 square metres.

ii)                    Southern sector.

Species contribution:

So again, oak is the dominant species with birch and rowan forming the secondary species. These results are based on amended data as there is some question about whether the species have been identified correctly in the field. As such, half the species composition data is made up of sample plot 5, which is being managed for oak timber production as discussed above.

DBH distribution:

Again just plotting the three main species (oak 48%; birch 17%; rowan 13%). This shows a large amount of young growth, but in many ways is skewed by sample plot 5 – the oak plantation.

Tree density:

Although the details of species and DBH has had to be amended owing to suspected recorder error, the tree density results are still valid. So based upon 156 records it is calculated that there are 343 trees per hectare, each tree occupying a space of 29.1 square metres.

Conclusions

Historic map evidence shows that Kinver Edge’s northern portion was population by trees before the southern portion. Tree density analysis, and DBH distribution does support this to some degree on the ground. Graphs could be interpreted as showing the southern samples are still recruiting a larger number of young trees than in the north, although coppice re-growth in the plantation will affect the results.

 

The relatively localised sampling method for a comparatively large area is inadequate, and the raw data does show a few repeating measurements as the same tree is recorded. As with the example of the localised aspen dominated area, known blocks of homogenous DBH birch and large samples of sycamore on steeper slopes are not reflected in the final results. Returning to record these will be useful evidence for future management planning.  

Thanks

Thanks has to go out to the working holiday volunteers who managed to pick up the survey technique and tree identification in less than an hour, and undertook the work in horrendous weather conditions.