The Use of Heather Burning as a Management Technique for a Suffolk Heathland

TRANSACTIONS THE USE OF HEATHER BURNING AS A MANAGEMENT TECHNIQUE FOR A SUFFOLK HEATHLAND PETER

NICHOLSON

THE cessation of sheep grazing during the period 1920-30 and the great reduction of rabbits by myxamatosis in 1954, profoundly changed the ecology of the Suffolk heaths. Heather (Calluna vulgaris) and Gorse (Ulex europaeus), left to grow unrestricted, dominated the coarse grasses that grazing encouraged, whilst the appearance of Birch seedlings (Betula pubescens) and Bracken (Pteridium aquilinum) denoted that the natural succession to woodland was unimpeded. Oak (Quercus robur) and Scots Pine (Pinus sylvestris) invaded more slowly from adjacent woodlands.

There is little doubt that unless some further major change in land use takes place, many of the heathlands in existence today will eventually become high oakwoods, the climax Community for much of Suffolk.

When the Nature Conservancy declared Westleton Heath (grid ref. TM458700) as a National Nature Reserve in 1956, the aim was to safeguard a typical area of open heathland. The major conservation problem was that no management technique was known, other than the traditional sheep grazing, that would arrest the succession of heath to woodland. This problem was urgent, for the interesting heather Community that covered the larger part of the reserve was already old and did not appear to be regenerating. Indeed, in some areas it had died and had been replaced by bracken and birch scrub.

This note concerns an experiment set up in March, 1959, to test the suitability of burning and mowing, commonly used in moorland heather management, for the management of a Suffolk heath. These techniques (particularly burning) had been used to a small extent in the past by local gamekeepers for heather management, but in the absence of accurate records it was feared that they might be hastening the succession to woodland. Tansley (1939) pointed out that bracken invasion was probably encouraged by heather burning, "since the bracken rhizomes, owing to their depth below the surface, are rarely injured by the fire, and they may easily occupy the ground before the moor plants have regenerated". Watt (1955) found that the number of bracken

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Transactions of the Suffolk Naturalists', Vol. 14, Part 1

shoots on Lakenheath Warren (West Suffolk) increased significantly in areas where overhanging heather fronds had been cut back.

These fears were supplemented by the views of McNaughton (1959) who from sheep farming experience had found that when heather over fifteen years old was burnt, the thick woody stems generated too much heat and the root stock was damaged.

This meant that new growth had to occur mainly from seed and the risk of bracken invasion and eventual dominance was much greater.

The experiments were carried out in March, 1959, on two sample plots of heathland approximately half-acre each. The first plot (Plot A) was selected because it already contained some bracken, and could be tested for increase in bracken density after treatment. This plot was dominated by Calluna but Cross-leaved heather {Erica tetralix) and Bell heather (Erica cinerea) were frequent. A complete list of the flora of this area is given as an Appendix. The experimental treatment was as follows:— the whole plot was mown of its surface Vegetation with an autoscythe set to cut close to the ground. The mowings were raked together into five rows approximately one metre wide and sixty metres in length, and burnt. Thus, both mowing and burning treatments were used on this plot. Sample plot B had no bracken growing on it and was selected to see if bracken would invade (by spores) an area in which it had not been previously present. Calluna was dominant and there were occasional patches of bell heather. In June, 1961, the surface Vegetation was mown close to the ground the mowings being left to decay where they were cut.

Analysis of plant cover in plot A was first made in June, 1959.

Ten random metre quadrats were examined for frequency of bracken shoots and the area of the ground occupied by the heather was estimated as a percentage of the area of the whole plot. In January, 1961, a further sampling was made by dividing the plot into five metre quadrats and counting the total number of bracken shoots in each quadrat. In 1967, plot A was sampled using both the methods of 1959 and 1961. Results for bracken counts were calculated as the number of bracken shoots per Square metre.

Plot B was carefully searched for bracken growth in 1961 and 1967.

Results After six years, there was no significant change in the percentage cover by Calluna in plot A {see TABLE 1). Similarly there was no change in the number of bracken shoots per Square metre using both the sampling methods of 1959 and 1961. No trace of the heather burning carried out in 1959 could be found, either as heather ashes or as a floristic difference between the burnt and unburnt areas.

HEATHER

BURNING

On plot B, no bracken shoots (or tree seedlings) could be found after careful searching. Calluna occupied most of the ground.

TABLE 1

Sampling 1959 1967 1961 1967

n 10 20 20 20

Number of bracken shoots per Square metre 3-20 ± 2-40 1-75 ± 1-09 2-59 ± 1 - 5 2 2-25 ± 1 - 3 3

% cover by Calluna 83-70 ± 6 - 8 4 79-50 ± 5 - 8 7 — —

M e a n n u m b e r of bracken shoots per Square m e t r e a n d % cover b y Calluna vulgaris on a half-acre area of heathland after t r e a t m e n t b y b u r n i n g a n d m o w i n g in M a r c h , 1959. M e a n s ± 9 5 % confidence limits. n — n u m b e r of samples.

In 1967, the heather on both sample plots was short (8 to 10 ins.) upright and vigorous, and it was a marked contrast to that on adjacent areas, which had a thick woody straggling growth (18 to 24 ins. high) containing frequent dead fronds. Numerous observations by Conservancy staff suggest that the treated plots are very attractive to small mammals and birds.

These results indicate that a single burning or mowing treatment on heather, approximately eighteen years old, was a satisfactory management method. Young fresh heather growth was encouraged whilst bracken did not invade to a significantly greater extent in a plot where it had had some previous holding, and did not invade at all in an area where it had not been present before treatment.

The heather burning technique is now being extensively used for the management of Westleton Heath N.N.R. Substantial areas are to be burnt in a five, ten or twenty year rotation and it is hoped that the Optimum rotation period will be found that will encourage the most varied and viable plant and animal life in the reserve.

Acknowledgements These experiments were originally set up by Dr. R. G. Pawsey.

The 1961 sampling was made by Mr. J. C. Taylor, now of the Ministry of Agriculture, Food and Fisheries, Tolworth.

References M c N a u g h t o n , A. (1959). M u i r b u r n i n g . A S h e e p F a r m e r ' s views.

Scottish Agriculture 1959, 157.

Tansley, A. G . (1939). T h e British Islands and their Vegetation. 2, 503.

W a t t , A. S. (1955). Bracken versus heather, a s t u d y in plant sociology.

Journal of Ecology 43, 490.

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Appendix

List of thefloraof plot A. Higher plants Calluna vulgaris, Erica cinerea, Betula Carex arenaria, Agrostis canina, Rumex Erica tetralix, Ulex europea, Molinia c Cuscuta epithymum, Chamaenerion ang Pteridium aquilinum.

Ferns Polytrichum juniperinutn, Ceratodon p Mosses Dicranum scoparium, Hypnum cupressif Lichens Cladonia sylvatica, C. comosa.