Llanelli Naturalists Newsletter - June 1996
R N Stringer & Jonathan Graham
Its Historical Significance And Importance For Nature Conservation
Native woodlands are an extremely important element in our landscape and over the last 10,000 years or so have been managed to varying degrees to provide fodder and shelter for stock as well as material for domestic, agricultural and industrial use. The extent of native woodland has declined tremendously over the last 5,000 years and the percentage cover of ancient woodland in Britain is about 2.9%, the lowest in Europe.
There are three types of semi natural woodland (as opposed to plantations) recognised in Britain today. These are:
- High forest - with standard trees close together, usually ungrazed with well developed shrub and ground flora.
- Coppice woodlands - with or without standard trees, regularly cut over and usually ungrazed.
- Pasture woodlands - stands of standard trees with little shrub development and regularly grazed.
The latter type of woodland is nowadays extremely rare in Britain but is characterised by the presence of large, old, over-mature trees growing in, at least partial, open canopy, and secondly, by the known history of the site and, where possible, its management. Such examples include the Old Royal Forests (eg New Forest, Hampshire). Wooded Commons (eg Burnham Beeches, Buckinghamshire) and the mediaeval deer parks. From Norman times onwards, hundreds of deer parks were created in England and Wales, and unlike the forests and commons were enclosed by pales - fences erected on earthworks around their perimeters to keep stock (mainly deer) within an area with the object of providing venison for the landowner during the winter months.
Many of these pasture woodlands have been lost but some survive as modern day parks used for public recreation.
The importance of the natural history interest of the parkland trees has only recently been recognised. In areas subject to relatively low levels of air pollution, the epiphytic flora (ie that which is present on the bark) is outstandingly rich particularly with regards to lichen species. These are specialised organisms composed of an alga and a fungus growing together. Whilst a few species are widespread and common, many are adapted to the sort of bark which can only be found on ancient trees (eg. sheltered crevices and long dead-wood).Because ancient trees are rare, many of these lichens are also rare. Their presence is also related to the age of the trees (especially oak) where the pH of the bark has become less acid over the centuries due to leaching. Over 200 lichen species have been recorded from some parklands and because of their poor ability to colonise new sites, some of these species indicate the long term continuance of trees being present at the site for hundreds of years. Woodlands with young trees may only support about 30 species, most of which occur in other habitats.
It is not only the outside of the tree that is important from a natural history standpoint. Many of these old trees are characterised by the internal wood undergoing some form of decay. This is a perfectly natural and highly desirable process which enriches the wildlife able to use the tree. The organisms mainly responsible for this internal heart rot are fungi and are evident in the autumn by producing large colourful brackets up the trunk of the trees. The fungi digest the woody element and convert the material into fungal cell tissue and their living contents, containing protein and forms of stored sugars. These materials can now be used by many species of invertebrate as a food source. Some of the 'dead wood saproxylic invertebrate' species (as they are called) are only recorded from these ancient slowly rotting trees and are mainly members of the Coleoptera (beetles). The life cycle of many is not yet fully understood but it is known that some have very poor powers of dispersal and rely on the continuity of dead wood at a site to survive. As such sites are rare it is not surprising that a number of these beetles are very rare in this country and are described as Red Data Book species.
Thus the presence of ancient trees, especially in parkland settings in areas of low atmospheric pollution are exceedingly important both for their landscape and wildlife features.
Dan Y Parc Parkland
Setting and history
This site was initially identified from ancient maps and modern air photographs by the Countryside Council for Wales in 1994 who commissioned The Natural History Museum to report on the quality of mature and over-mature deciduous trees in selected parkland sites in Wales with respect to their value for the conservation of rare and scarce saproxylic invertebrates.
The site is c 20 ha in size situated on the eastern side of the A483, 4km north-east of Llandovery. The site is important historically as it was marked as parkland on maps dated 1607 and 1610, and was one of only two present in Carmarthenshire at this time. It may represent the remains of an ancient deer park as palisade fencing is highlighted on the map and there is evidence of the location of this feature in parts of the site today. The landholding was originally part of the Glanbran Park Estate, residence of the ancient family of Gwynne (who were reputedly descended from Brychan Brycheiniog) from the early 1500's until 1875. The most influential member of the family was Sackville Gwynne (1723-1793) who was famed for his performances on the Welsh Triple Harp. However, in his later years he managed to squander his wealth and ended up as a cab driver in Liverpool (R H Davies, pers. comm.).
The site is presently under multiple ownership and most of the present day management is grass production and stock rearing with areas divided into paddocks by hedgerows. A few large native trees are present in the hedgerow system but the principle feature of the site is the stock of ancient pollard oaks scattered in the open pasture.
An initial survey of the lichen flora on part of the site was carried out by R G Woods (of the Nature Conservancy Council) in 1981 and repeated by Countryside Council for Wales staff in July 1995. The dead wood invertebrate survey was carried out by National History Museum workers in July 1994 who also collated data on the physical condition of 18 trees. In August 1995 RNS and JG (CCW) revisited the site to carry out a fungus survey and complete the descriptive survey of the remaining trees. The results of the survey are summarised below.
Fifty five trees were investigated in total with most of the trees grouped towards the south-east of the site. Most of these trees, ranging in circumference from 3 to 7.4m, were mainly grouped into the top end of the range with over 48 percent between 5 and 7.4m. Almost all are hollow from base to crown, with little rotted heartwood remaining although 19 trees did show evidence of the heart rot fungus Fistulina hepatica which resembles a beef steak and one colonised by the sulphur yellow brackets of Laetiporus sulphureus. Most trees have substantial splits or openings in the main trunk and in two instances less than half of the outer shell of the trunk remained. Many of the trees had characteristic burring on the main trunk and some showed evidence of previous lightening strike. One tree had also been burnt on the inside. Although most of the trees exhibited scars of large boughs lost from the crown they looked very healthy and contained very little dead wood. Of the 54 trees examined 50 were oak. However, one ash tree was in a very poor state with over 80% of its crown dead.
Recording of lichens was mainly concentrated on the main trunk. Eighty-nine species of lichens were recorded from the site with 15 species of epiphytic mosses and liverworts. The number of lichens recorded ranged from 1 to 25. The main types recorded included members of the Cladonia, Lecanora, Parmelia and Pertusaria genera. Some species were ubiquitous (Evernia prunastri, Parmelia saxatilis, Pertusaria hemisphaerica) whilst others (eg Rinodina spp.) were more restricted in their distribution. The distribution of certain lichens was restricted to specific niches on the trunk. Species such as Chrysothrix candelaris, Arthonia impolita, Schismatoma decolorans and Lecanactis abietina were located in the drier crevices of bark away from direct rain whilst others such as the Parmelia species and Evernia prunastri occurred on the more well lit south facing parts of the tree. Rinodina isidioides and Normandina pulchella were associated with the wetter moss dominated areas of the bark.
Other species such as Parmeliopsis aleurites and Trapeliopsis spp. were only found on decorticated (debarked) wood. Many of the Parmelia species are sensitive to pollution from acid rain and the presence of P. perlata, P. reddenda and P. exasperata indicates that the site is not suffering badly from aerial pollution. This is also confirmed by the low abundance and distribution of Ochrolechia androgyna and Diploicia canescens - species tolerant of pollution and known to be spreading in the UK.
The site also contained 13 species which have been found to be indicators faithful to old forest areas, particularly pasture woodlands. These include Cetrelia, Cladonia parasitica, Chrysothrix, Lecanora jamesii, L. sublivescens, Pertusaria multipuncta and Rinodina isidioides. The latter species is nationally scarce within the UK. Also present was Caloplaca herbidella which is a nationally rare species (<15 10km squares) in Britain. C. herbidella was only found on one tree during the 1995 survey whereas it was found on 4 oaks in 1981. Species not recorded elsewhere in Carmarthenshire and scarce in mid Wales include Parmeliopsis. aleurites, Pertusaria flavida, Opegrapha lyncea and Chaenotheca hispidula (the latter 2 found in 1981).
As well as the species composition of the lichens present on the site the mix or community type is also important. A characteristic lichen community associated with ancient trees rather than ancient woodland is the Lecanactidetum premnea association. This is normally found on trees 250-300 years old or more, mainly old pollard oaks, whose bark has become dry and brittle with age. The main species characteristic of this community is Lecanactis premnea with associated species such as Lecanactis lyncea and Pertusaria hemisphaerica, both present at this site. This association is only better represented at Gregynog (Newtown) and Dinefwr Park (Llandeilo) in the whole of Wales.
Invertebrate sampling has only been undertaken once at the site in July 1994. Twenty-one species were found, 6 of which were associated with dead wood. One of these, Schizotus pectinicornis, has a highly localised distribution in Britain where it is restricted to Central Wales, Herefordshire, the Western Isles and Highlands of Scotland. One additional species, Scraptia testacea, listed as a Grade 1 indicator of the continuity of dead wood habitats in ancient woodlands has not been previously recorded from Wales and the adult record from Dan y Parc indicates that a breeding population is present on site.
Summary of the importance of the site
Dan y Parc is an unusual site as it contains a number of ancient pollard oaks that are evidently of parkland origin in what is now an agricultural setting exhibiting a few other parkland features. The site's pollard oaks are reminiscent of those found at sites, such as Moccas Park (Herefordshire) or Richmond Park, celebrated for the relict saproxylic invertebrate assemblages that they support. A few of the oaks at Dinefwr (Llandeilo) and even fewer at Old Cilgwyn (Cardigan) are of the same type and probably of much the same vintage, but it would seem likely that no site in the western half of Wales has as many large ancient pollard oaks as Dan y Parc.
The presence of rare lichen and saproxylic invertebrate species is a bonus and again highlights the extreme importance of the site from a nature conservation interest. The presence of the invertebrate Scraptia testacea at this its only Welsh location and extensive lichen growths of Caloplaca herbidella (probably the most extensive in Britain) ensures that this is a key site in the UK for these species.
Because of the importance of Dan y Parc it is essential that the site is managed to maintain the current interest and ensure that this interest survives into the future. With this in mind it is envisaged that the site will be entered into the CCW Tir Cymen countryside stewardship scheme which will allow positive management works to be carried out on site. These will include adopting best agricultural practices to ensure that the lichen interest will not be harmed through fertiliser or herbicide usage and the retention of as much dead wood to maintain the invertebrate interest.
Also, young trees will be planted to ensure a succession of trees in the future to allow the spread of lichen and invertebrate species.
Tir Cymen staff have been liaising with the landowners of Dan y Parc over the last 12 months to agree suitable terms over entering the site into this countryside stewardship scheme. It should also be noted by readers of this article that the parkland is under multiple ownership and there is no public access to the site at present. However, further detailed information on the site can be obtained from the authors.