The New Forest is the best example of a large heath surviving in full use. To safeguard this vital habitat from the threat of human impact & third sere succession - the heath turning back to mixed woodlands - it is currently being considered for National Park status. This is recognition of the New Forest as “… a unique survival of medieval Europe… (& that it is) internationally important to nature conservation & biological science.” (2).
FIELD METHOD:
The field method used to study the topographic changes in vegetation & soil was a belt line transect. A rope measuring 100 metres was taken (in a straight line) from the bottom of the valley at Dead Mans Hill, which was boggy land, up to the dry heath at the top of the slope. A sample station was created every 5 metres along the transect. Several different techniques were used to collect & analyse the data:
- To record the vegetation present we used the interrupted quadrant technique. At each sample station a quadrant was placed either side of the belt line. The percentage cover of both quadrants was recorded. Later the 2 quadrants percentages were added together to create just 1 percentage for each species of vegetation present at the stations.
- At each station the surface & the soil temperature was taken using a thermometer.
- To establish a topographic profile of the belt line transect, a 5 metre line, spirit level & a 1 metre ruler were used to record the gradient changes between each station. Starting from the top of the 100 metres, the 5 metre line was held closely against the ground. It was then taken to the next station where the 1 metre ruler was held horizontally. Using the spirit level to ensure that the 5 metre line was even, the distance between the second stations ground level & the horizontal 5 metre line was measured.
- A small soil sample was also taken from each station using a trowel. These soil samples were then stored in plastic bags or storage containers for a week until further tests could be carried out.
Soil pH:
A week after the sample collection took place a pH test was carried out, using a BDH kit. To do this 2 cm³ of soil was placed in a test tube. To flocculate the clays, 1 cm³ of barium sulphate was added to the soil in the test tube. Then distilled water was added to the mixture to make it up to 10 cm³. 2 cm³ of indicator solution was also added & the whole test tube was shaken well. It was allowed to settle before the result was compared with the BDH kit chart. This was repeated for all 21 soil samples.
Soil Moisture Content:
The technique that was used to measure the soils moisture content also took place a week after the samples were collected. To measure the moisture content a crucible was weighed. A small sample of soil, from which most of the roots & litter had been removed, was placed in the crucible - which was then reweighed. The soil filled crucible was then placed in an oven for 8 hours at 90°C. The crucible & its contents were then weighed again. The weight of the crucible was then subtracted to give the mass of the dry soil. Then the percentage of moisture content was calculated:
Mass of wet soil - mass of dry soil x 100 = % of water (by mass) in soil
Mass of wet soil
The process & calculation was carried out for each stations soil sample.
Soil Organic Matter Content:
Using the dried soil samples from the soil moisture tests, each crucible was individually heated by a bunsen burner to burn off the organic matter. The crucible was then allowed to cool off before it was reweighed. The heating & cooling off was then repeated until there was no further change in the weight. The mass organic matter was calculated:
Organic matter (G) = mass of dry soil - mass of strongly heated soil
This was repeated for each soil sample, the percentages were also calculated.
LIMITATIONS:
- The field work & investigative tests were carried out by small groups of students. This could have distorted the findings as techniques may have varied & been inconsistent. Each group was made aware of what & how the data needed to be obtained to keep it as consistent as possible.
- The soil samples may have given different results had all the tests been carried out on the same day rather than a week later.
- Although trouble was taken to correctly label samples & record data, the sample station data from both 10 metres & 80 metres became contaminated by human error. This meant that no comparison could be drawn from these stations. This could have been avoided if there had been a less pressurised time limit to the field work & tests.
- Therefore the time limits on the data collection may also have meant that there was less accuracy in the other recorded results.
RESULTS:
For the purposes of this investigation the results have been summarised in these tables and graphs.
For complete data please see the Appendices.
TABLE OF SAMPLE RESULTS:
RESULTS TABLE FOR VERTICLE DISTANCE:
SUMMARY OF QUADRANT RESULTS:
DATA ANALYSIS:
The study at Dead Mans Hill produced typical heathland results. The vegetation was very much representative of heathland plants & this was reflected by the quadrant results. However the absence of gorse was not reflective of the slope as a whole as there was substantial gorse coverage of Dead Mans Hill. The stations at 70 - 80 metres had the highest percentage of gorse cover & this, for a large part restricted the presence of ling & cross leafed heath but not bell heather. Aside from this the variety of vegetation was indicative of heathland shrubs which can tolerate soil with a poor nutrient quality & low pH.
The pH levels at the sample stations showed that the acidity of the soil was in keeping with heathlands pH range, 3.5 - 6.7. As the slope rose from stations in the boggy valley to the top station at 100 metres the pH dropped. This is also reflected by the vegetation present. There were no acidity sensitive lichens present until the last 20 metres of the slope.
The pH also ties in with the moisture content of the soil samples. Ling heather does not like wet conditions. As the slope rose the soil became drier & the pH lower. Therefore the percentage cover of ling also increased dramatically. In the moist valley there is very little ling cover.
This is not true of cross leafed heath which is tolerant of wetter more acidic soil & has a significant presence in the stations with a higher moisture content. Cross leafed heath petered out up the slope as the soil becomes freer draining. However its presence in the station at 100 metres may represent the increase in moisture content at this station which is not reflective in the trend for moisture content of the soil sampled. This may be due to a less eroded patch of soil at this station, which may have been protected by the vegetation above it.
Bell heather likes dry conditions. This is reflected in the absence of coverage in the moist soil of the valley stations & the occurrence during the last 40 metres where the soil was marginally drier & freer draining.
The percentage cover of grass peters out up the slope as the heathers become more prevalent. The valley grass is well established & has been grazed since medieval times; it also forms part of some of the track. However its absence in the higher stations may be due to this prevalence of the heathers.
There was a higher percentage of moss coverage in the last 20 metres which ties in with the presence of lichens. The pH was lower here as was the moisture content. However the organic matter content was higher. As was the dead leaf litter.
The dead leaf litter cover is reflective of the ling coverage & is part of the process of the leaching of nutrients to form the iron pan which creates the acidic wetland habitat at the bottom of the transect.
The small but significant presence of bog land tolerant tormetil is also representative as it does not occur any where else on the transect apart from the stations in the valley with a high moisture content & a more acidic pH.
The high level of organic matter present at the stations between 40 metres & 55 metres is also representative of the proportionate coverage by ling & cross leafed heath.
The soil & surface temperature show little fluctuation & are also representative of the temperate conditions necessary for heathland. The rise in soil temperature over the last 15 metres of the transect may reflect the high coverage of insulating ling & mosses. The dead leaf litter percentage may also have contributed to the insulation of these stations. Similarly the gorse coverage between 70 & 80 metres may also account for the fluctuations in surface temperature as the gorse created shelter for any wind that was present.
Therefore the data collected from the belt line transect at Dead Mans Hill provided typical lowland heath results & reflected some interesting findings with regards to the ecosystem of a heathland environment & the changes between its vegetation & soil.
In order to expand the contrasts between heathland & wetland vegetation & soil it would be valuable to conduct a similar investigation into an area that is solely heathland & then solely wetland. It would also expand the investigation if upland heath was included. A study of valley & hillside vegetation & soil, in all of these locations would also provide interesting data to expand the investigation.
To further understand the relationship of heather & heathland a study into the regeneration of heather after a controlled burning had taken place could be conducted (8).
CONCLUSION:
The main findings of this study of vegetation & soil down a slope in the New Forest are that this sensitive environment is intricately balanced by the maintenance of its vegetation & soil.
Typically the soil acidity ranges between 4.5 & 6.5. The free draining soil & the ling formed iron pan are represented in this environment. This is how the wetland at the bottom continues to be so acidic & why the vegetation is that of nutrient poor tolerant plant life.
The prevalence of ling, cross leafed heath & bell heather is also reflective of typical heathland vegetation. As is their location eg: ling & bell heather in dryer soil & cross leafed heath in moister soil. This also applies to the abundance, absence & location of the other species at the site.
Therefore the findings & conclusion of this study is that the relationship between the vegetation present & the soil it survives in on Dead Mans Hill is typical of lowland heath.
BIBLIOGRAPHY:
- “The History of the Countryside” by O. Rackham, published by Phoenix in 1986, page 282-304.
- www.newforestassociation.freeserve.co.uk/info.htm
Last updated 2/10/2002, page 2 of 7.
- “Geography Society - Heathland Ecosystems in the UK” by M. Fenwick, © RedPen Internet Solutions in 1998, page 1-3.
- “Portrait of the New Forest” by B. Vesey-Fitzgerald, published by Robert Hale Ltd in 1966, page 14-15, 175-197.
- “Heaths & Heathers” by T. Underhill, published by David & Charles Publishers Ltd in 1971, page 23-83.
- “British Wildlife Journal, Volume 11, Number 4” by L. Haskins in April 2000, page 229-237.
- “Ecosystems & Human Activity” edited by J. Woodfield, published by Collins Educational in 1994, page 92-98.
- “Techniques & Fieldwork in Ecology” by G. Williams, published by Collins Educational in 1991, page 132-135.
APPENDICES:
COMPLETE QUADRANT RESULTS 1:
COMPLETE QUADRANT RESULTS 2:
COMPLETE QUADRANT RESULTS 3:
SUMMARY OF QUADRANT RESULTS:
COMPLETE RESULTS TABLE 1:
COMPLETE RESULTS TABLE 2:
RESULTS TABLE FOR VERTICLE DISTANCE:
