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Suffolk Natural History, Vol. 35
ANCIENT H O R N B E A M TREES IN BURGATE WOOD, SUFFOLK J. WHITE AND N. SIBBETT Burgatc Wood is an ancient coppice woodland south-west of Diss (TM075757) covering 30-5 ha. It has much hazel coppice and areas of hornbeam coppice, with a light Cover of oak Standards mostly under 70 years old. Ancient coppice stools, particularly of ash, are abundant. The south-east quarter of Burgate Wood contains historic earthworks, including a moat which has recently become a scheduled ancient monument. Amongst these earthworks are fourteen ancient, mostly pollarded, hornbeam trees. Burgate Wood is on thc western edge of a native hornbeam stronghold within East Anglia (Perring & Walters, 1990). The trees in the wood are likely to be descendants from the original native stock, although it is not possiblc to teil if they have grown naturally or were planted. It is unlikely that, in a hornbeam area, hornbeam would have been brought in from elsewhere because it was an unpopulär species; its wood is hard to work and its use is limited compared with ash, oak and hazel. English Nature commissioned John White, a Consultant dendrologist, to study the trees to aid management decisions. Ash coppice stools in Burgate Wood were measured, the largest being 232 cm in diameter. This is 79 cm greater than the largest stool in Hayley Wood, Cambridgeshire, which may be 400 years old (Rackham, 1986). At Silk Wood, Gloucestershire, large ash stools investigated by Rackham were found to be growing at the rate of 1 cm diameter every 7-5 years. At this rate, the Burgatc Wood ash stool could have 300 years more growth than the Hayley Wood ash, making it 700 years old. Hazel and maple stools have also been measured in Burgate Wood and are of comparable age. The ancient hornbeam trees are believed to be contemporaneous with the ash, although hornbeam is not well researched (White, 1998). Each of the fourteen ancient hornbeam trees has been tagged with a numbered aluminium label on the north side between 2 and 2-5 m above ground. The stem diameter has been measured, and the basal area of the stem has been calculated from this. The basal area is of great help in determining the age of trees. In thc first decades of a tree's life, growth is fast and the rings wide. After "maturity", trees tend to increase their basal area by the same amount each year. As the diameter gets bigger, each annual ring is slightly narrower than the previous one but has the same cross-sectional area. The age of a tree can be detcrmined from its diameter basal area, the width of thc recent annual rings, and measurements or estimates of its initial fast growth. Ring growth on branches can be used to estimate early tree growth, and two broken branches were found to be 68 years old with 2-5 mm average ring width. The structure and height of each tree was also measured. The objective for these old trees is to maintain them for as long as possible, hopefully for many more centuries. The key factor is maintaining the life of the "bolling" or trunk. To do this, the branches must be kept free from competition from adjacent trees. If the branches grow too heavy for the bolling, they may collapse and split the bolling into pieces. Specific management äctions are planned for each tree, which includes reduction of surrounding Vegetation,
Trans. Suffolk Nat. Soc. 35 (1999)
ANCIENT HORNBEAM TREES IN BURGATE WOOD
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1 he map shows that the hornbeam trees do not appear to be located in any particular order relative to the earthworks or to each other. It seems likely from undulations on the ground, that several more similar sized specimens once stood on this site partial pollarding to remove larger limbs, and frequcnt monitoring Droueht or diseases such as the bracket fungus, Bjerkandera adusta which infect stressed trees are beyond human control. The age of some of the trees could be greater than we think. Trees 1 and 2 are 1-5 m apart; they may have once been a Single plant whose centre has decayed to leave two parts separated above ground (see Plate 17) ir they were once united as a Single plant the basal area would have been around 4 5 000 cm*, representing an age of over 1,000 years. Similarly, the clump of five stems ? L n e e 5 ' m a y ° n C C h a V C b e e n a s i n § l e P l a n l a n d a l s o c o u l d therefore be over 1000 years old. Genetic analysis of their leaves might demonstratc the origins of these plants. The technique is getting cheaper and a lot of genetic analysis is being carricd out on black poplar at present. If resources can be found this work would be of great help. Knowledge of the age of the trees helps archaeologists to understand the age ol the earthworks. It is reasonable to assume that the earthworks were free ol trees when constructed, and they would have been maintained free of trees lor an unknown period. A 700 year old ash or hornbeam on an earthwork means that the earthwork is at least that old.
Trans. Suffolk Nat. Soc. 35
(1999)
ANCIENT HORNBEAM TREES IN BURGATE WOOD
121
The exact age of the hornbeams can only be measured by counting all the rings, or estimating the rings of any hollowed-out trunk centres. Tree number 13, which is blown down and partially alive, is suitable for investigation. It would be acceptable to cut the trunk near the base, to take a section for tree ring analysis. The tree might possibly regrow, but in any case is likely to continue to slowly die so there would be little conservation disadvantage if it died immediately. The slice of trunk would need to be prepared carefully for analysis with a microscope. It is not a task that can be done by an untrained person, so resources would need to be found to achieve this. Burgate Wood is private with no public access. Occasionally the Upper Waveney Valley Project has a summer tour in aid of Burgate Church. Details can be obtained from their project officer, Mark Timms, on 01379 788008.
References Perring, F. H. & Walters, S. M. (1990). Atlas of the British Flora. Botanical Society of the British Isles, London Rackham, O. (1986). The history of the countryside. J. M. Dent and Sons Ltd, London White, J. (1998) Estimating the age of large and veteran trees in Britain. Forestry Commission, Edinburgh John White 8 St Andrews Drift Langham Holl Norfolk NR25 7AG
Nicholas Sibbett English Nature Suffolk Team Regent House 110 Northgate Street Bury St Edmunds Suffolk IP3 3 1HP
Game cover as a source of unusual alien plants In Autumn 1998 I investigated several fields of game-cover being grown around Sotterley and Wrentham. Whilst the main crop was Sunflowers, Helianthemum annuus L. and Maize, Zea mays L., there were many other species mixed in; some were obviously intended as additional food sources, others were probably accidental inclusions in the mixture. T w o large plants of Ragweed, Ambrosia artemisiifolia L. were over 6 ft. fall and matched the form previously classed as A. elatior L. but now included in the above species. There were many other unusual species including Green Pigweed, Amaranthus hybridus L„ Common Amaranth, A. retroßexus L., White Pigweed, A. albus L„ Quinoa, Chenopodium quinoa (Willd.), Bullwort, Ammi majus L„ Buckwheat, Fagopyrum esculentum Moench, Cannabis, Cannabis sativa L., Buffalo-bur, Solanum rostratum Dunal (see Plate 16), Rough Cocklebur, Xanthium strumarium L„ Spineless Saltwort, Salsola kali L. ssp. ruthenica (Ujin) Soö, Japanese Millet, Echinochloa esculenta (A. Braun) H. Scholz, White Millet, E. frumentacea (Roxb.) Link, Rough Bristle-grass, Setaria verticillata (L.) P. Beauv., Green Bristle-grass, S. viridis (L.) P. Beauv., Witch-grass, Panicum capillare L. and Johnson-grass, Sorghum halepense (L.) Pers. It is likely this sort of crop will continue to be a source of introduction for such unusual aliens. T. R. Abrehart. 4 6 - 4 8 High Street, Wrentham, Suffolk N R 3 4 7HB
Trans. Suffolk Nat. Soc. 35
(1999)
Plate 16: Buffalo-bur, Solanum rostratum Dunal, weed in game cover crop at Sotterley, Autumn 1998 (p. 121).
Plate 17: Ancient Hornbeams at Burgate Wood (p. 120).