Happy Birthday to Us
Sidmouth Arboretum Celebrates its Tenth Birthday
Lots of our friends and supporters came together for a tenth birthday party in the grounds of Sidholme on Sunday 8th May. Guests were treated to guided walks around the wonderful trees in Sidholme and entertainment from the Sidmouth Folk Choir and Jurazzic traditional jazz band. There was a cream tea two cakes. We have to say a big thank you Ali, Sidholme’s new owner, for allowing us to use the grounds while the hotel is closed for refurbishment. We wish him all success when the work is finished and he can re-open for guests.
The party came at the end of a busy Tree Week where we had extra guided walks, including a guided tour of Bicton led by Mick Street, and a Zoom talk on Ancient Woodland by Ed Dolphin.
There are more pictures saved in Dropbox
The next major event will be more planting for the Queen’s Green Canopy in the autumn, more on that later.
Sidmouth Arboretum has helped to replace a well-loved Family Tree.
In 1993, EDDC joined with the UK Tree Council to celebrate National Tree Week by planting Family Trees. Local multi-generational families were given trees to plant. A Red Oak was planted in the grounds of the council offices, Knowle. It was planted by four generations of a local family, headed by Dorothy McGuigan.
Articles about Knowle trees on Facebook prompted Dorothy’s granddaughter, Sharon MacKay, to contact Sidmouth Arboretum asking about their tree. Arboretum volunteers did some research and found that the tree had died. It was replaced by a new tree planted in memory of a popular council employee, Jane Cuthbe. The Arboretum agreed to replace the original tree in a new site.
Family members came together to plant a new Red Oak in the park of the Knowle last Sunday. Sadly, Dorothy is no longer with us, and Megan MacKay, the youngest family member at the original planting, is serving in the army and not able to get away. They were represented by Dorothy’s youngest daughter, Teresa Cooper, and her husband Rob.
The family was assisted by councillor Kelvin Dent, Chair of the Knowle Residents Association. KRA volunteers hope to play an active part in caring for the park and gardens of Knowle when they pass to the Town Council next year.
HEDGE SURVEY INTERIM REPORT
Hedges 2020 An Interim Report, June 2020
In 2014 Sidmouth Arboretum undertook a survey of the valley’s trees, now they are following up that work with a study of the agricultural hedges.
The 2014 Survey* revealed that, apart from nearly half a million trees, there are over 500Km (300 miles) of hedges currently enclosing farmers’ fields in the Sid Valley, and they play an important role in the valley’s appearance and ecosystems.
Using a computerised geographical information system, Arboretum chairman Jon Ball made a random selection of 100 fields across the valley, and then selected one side of each field to be surveyed.
Thank you to the volunteers who have been out estimating the dimensions of the hedges, their state of maintenance, the presence of standard trees and the maximum size of those trees, the variety of woody species in the hedge, and the range of herbaceous plants associated with the hedges. In Devon, the term hedge often refers to a bank planted with shrubs and trees and many of the hedges in our survey fit that description, but some do not include the bank. If there is a bank, the height of the hedge is recorded as the height of the growth, that is what is above the bank.
Summary of Aims
The Hedge Survey has four main aims:
1) Establish the hedgerow species diversity
2) Establish the scale of standard trees in our hedgerows
3) Estimate the age of hedges
4) Establish the floral diversity in our hedgerows.
With more than half the sample now surveyed, this is an interim report on the findings. This report, being interim, concludes with a brief look ahead and a summary of the data. The final report will include a list of action points that need to be addressed if future generations are going to enjoy the same level of amenity provided by our wonderful hedgescape.
Woody Species Diversity
It is clear that, although this is a small, self-contained valley, the diversity of form, structure and quality of our hedges is wide, possibly more so than in areas of intensive farming such as parts of North West Norfolk.
Some of our hedges are clearly very old, some have been planted more recently, there will be a separate report, Hedges 2020 Historical Changes to follow this report. The differing geology, topography, and history across the valley support a wide variety of species profiles in the hedges. Many areas have a mix of Hawthorn and Blackthorn and a good variety of other woody species. Two thirds of the hedges have more than five woody species. Some of the hedges in the larger fields are in distinct sections, perhaps a stretch of Field Maple and then a stretch of Hawthorn or Blackthorn. In some cases, this is linked to previous field patterns where the different stretches used to be in separate fields that are now amalgamated. In other cases, a farmer might have revitalised a neglected hedge with a new planting where the old hedge had failed, but they have used a different species.
In some of the upland areas, particularly the areas on Greensand, Beech predominates in hedges that were planted as the open heath was enclosed in Victorian times. The fields to the north of Sid Road from Fortescue to Sidford, although known to be at least two hundred years old, appear to have been planted more recently and are made up of Elm mainly. Two thirds of the hedges surveyed so far are traditional Devon Hedges in that they are planted on a bank, sometimes just earth, others supported by stone cladding. This includes some of the hedges that have clearly been replanted comparatively recently.
Many of the hedges are maintained regularly, others have been neglected for decades and have grown into lines of trees rather than a hedge, these are known as relict hedges. Some of the relict hedges were once maintained by the traditional practice of hedge laying where upright growth is half cut through, laid down, and branches are woven together to form a stock proof barrier. A small number of the well-maintained hedges show evidence of having been laid comparatively recently, but the majority are maintained by tractor mounted flail.
There is a negative correlation between a hedge being left untended and relict and having a wide range of woody species. There is some correlation between being sited next to a road and the hedge having multiple species of woody plant. Whether or not a hedge is banked does not appear to influence the number of woody species.
One of the main aims of the study was to establish the condition of standard trees, trees allowed to grow to maturity spreading their canopies above the hedge. Standard trees are very important in the appearance of the valley and to wildlife. Our standards are part of a group known as Trees Out Of Woods (TOWS). TOWS have ecologic impacts far beyond the proportion of land they occupy, by increasing the permeability and habitat value of the whole landscape. **
Of the valley’s estimated tree population of nearly half a million trees, the survey suggests there are about 38,000 standard trees in our hedgerows. Often, these standards are pollards, trees cut off at the height reached by a man with an axe to keep the new growth out of reach of browsing livestock. This used to be common practice because the wide spreading crowns provided shelter for livestock and repeated pollarding, like coppicing, provided valuable timber for craft and woodfuel.
Modern maintenance by tractor mounted flail means that maintaining standard trees happens less often now, and the majority of the standards are the mature trees left by previous generations in the old hedges and they are coming to the end of their lives, particularly the Ashes, but more on that later.
Our valley’s hedges still have a good stock of mature standards, but the tidy, maintained hedges, which make up half the survey sample so far, have fewer standards per 100m than other hedges. The difference is even more marked when it comes to young trees that could grow into mature standards in the future, tidy flailed hedges have far fewer young trees per unit length. One possible action point is to work with farmers to promote the idea of leaving more of the young trees in the regularly maintained hedges to grow as standards. This will involve the farmers in extra work and a good cost benefit analysis would have to be made.
It is true generally that older hedges have a wider range of woody species in their length. In the 1960s, ecologist and historian Max Hooper used a wealth of observations and archive evidence to propose a method of dating hedges which became known as Hooper’s Rule. Dating a hedge is not a precise science and, with modern farming trends, it is becoming less reliable, but Hooper’s Rule is still a useful guide. The rule states that the number of woody species in a 30 yards length of hedge multiplied by 110 gives you the age of the hedge site in centuries. The explanation is that, although hedges are usually planted as a single species, a Hawthorn or a Field Maple hedge for example, other species are introduced by natural processes of seed dispersal as time passes. Saying that a hedge is 500 years old does not mean that is the age of the trees and shrubs currently making up the hedge, although this might be true for the occasional ancient Oak standard. It means there has been a field boundary on this site for that length of time with a succession of trees and shrubs. Hedge 611N in our survey has 13 woody species in its length. If you took any 30 yard section, it contains at least 9 of these and so, x110, the rule suggests there has been a hedge on that site for about 1,000 years, but the oldest tree in the hedge is an oak that is about 200 years old.
Modern hedge planting often includes multiple species as a deliberate choice. Sidmouth Arboretum has planted three hedges in the last year each of which were a mixture of five species. If a researcher surveyed the hedge five years from now without knowing the history, and simply applied Hooper’s Rule, they would conclude the hedge had been in place for 550 years. In the case of 611N, there is other evidence that backs up the conclusion about the age of the hedge, but that will be covered in the separate Historical Changes report.
Hooper’s Rule may have some problems, but it is certainly true that ancient hedge sites, as with ancient forests, tend to have more woody species than younger hedge sites and this diversity is considered a good thing from an environmental point of view.
There is a strong correlation between the hedges in the valley with many woody species and a diverse herbaceous storey underneath.
Where hedges are associated with a rich variety of herbaceous species this provides a good base for a food chain that will support many types of invertebrates, and small vertebrates, particularly birds and small mammals. See above for a list of herbaceous plants recorded so far. Some names are generic and cover a number of species, for example more than one type of Buttercup was found, but the list was a secondary purpose of the survey and received less attention during recording. Also, the visible species change during the year, some of the sites were surveyed before summer plants emerged and others were surveyed after early spring plants had died back. It is beyond the scope of this study to record the myriad species of invertebrates that live in the hedges.
Nineteen of the 59 hedges surveyed so far were rated as having a good range of herbaceous species, 24 were medium, and 16 were poor. The distribution of good and poor diversity was not even across all hedge conformations.
Possibly contrary to some expectations, the hedges kept under control with the flail had slightly better diversity in their herbaceous storey overall, 50% of the hedges surveyed are flailed but they represent 64% of the hedges rated as good for herbaceous diversity and only 25% of the poor hedges.
However, this is not a straightforward picture because there is an interaction between management method, structure, and location. Half of the flailed hedges are on a roadside where they have to be kept under control for road safety reasons, and more than half are banked. Roadside hedges and banked hedges are more likely to have a very long history and, as might be expected, they do have a disproportionate share of the good herbaceous diversity. The widest diversity is found with the banked hedges on old, quiet lanes such as Harcombe Lane and Milltown Lane, one of which is flailed and one not.
If you move away from the roadside to the hedges between fields, 18% of the flailed hedges have good herbaceous diversity compared to 25% of the unflailed hedges. However, 18% of the flailed hedges have poor diversity compared to 40% of the unflailed hedges. These results are skewed by the relict banks on the high ground which have grown out as lines of Beech, the canopy of Beech trees is dense and shades out the herbaceous layer almost completely. Other flailed hedges are in arable fields where cultivation, including some spraying, is taken right up to the hedge. The numbers are too small to draw firm conclusions, but the overall impression is that flailed hedges can support a rich and diverse herbaceous storey. The effect on animal diversity is beyond the scope of this study. Of the two laid hedges, one was rated with good diversity, the other poor.
There are clouds on the future horizon that threaten our trees and hedges. The long-term threat to the hedges themselves from climate change is unquantified, but there are serious concerns about the impact of climate change on our standard trees. Standard trees are a key part of the visual and wildlife value of the hedges. Away from the upland areas, Ash and Oak standards are the two main species. Many of the standards are succumbing to age and there is a potential threat to the Oaks from a disease called Sudden Oak Death, but that threat to our valley’s appearance and biodiversity is much lower than Ash Die Back.
The 2014 Tree Survey revealed that Ash is the dominant deciduous tree in the valley. Ash trees are 10.7% of the tree population and provide 18% of the total leaf area. Their importance is even more significant because they support much more of our local biodiversity than the larch and Douglas Fir which are the most numerous trees. To lose our Ash trees will be as devastating to the landscape and ecology of the valley as Dutch Elm Disease was several decades ago across southern England.
Ash Die Back is a fungal disease that spread from Asia where the native Ash species have evolved resistance to its effects, our trees do not enjoy that resistance. The fungus invades and blocks the water transport xylem of the tree and eventually the tree dies. As was said, Ash is the dominant broadleaf tree in the valley and, as a native tree, it supports a wide range of other species. The loss of most of our mature Ash trees and the loss of young trees to succeed the old trees will not only affect the landscape, but the valley’s invertebrate biodiversity with a knock-on effect on vertebrates, particularly birds.
The stark numbers are that of the 59 sites surveyed, 50 have Ash present either as a tree or shrub or both. Of the sites with Ash present, 30 have signs of Ash Die Back, 14 of them have evidence of significant infection. It is not possible to stop Ash Die Back; you cannot inoculate nearly eight thousand trees, forty thousand if you include the trees in woodland, even if there was a tree antibiotic. It is possible that some trees will show resistance and survive to breed new stock, but that will be a long-term process that I will not see. The outlook for the next few years is not promising.
To conclude, the overall picture is that our hedges are in a fairly good state, with the exception of the younger but now relict ones on the high ground. There is good diversity in hedge type and the natural biodiversity they support. Things could be improved further with the help of farmers committed to our aims. Action needs to be taken to allow standard trees to be replaced if we want the appearance of the valley to be maintained, but the replacements will have to take account of climate change and tree pathogens.
We await the data from the remaining hedges to be surveyed which may or may not cause major changes to these observations. The data present a springboard into other investigations to explore particular aspects of our wonderful network of hedges. A full report will be published when we have all the data.
Ed Dolphin, with thanks to all the volunteer surveyors, and to Jon Ball and Diana East for their help with editing this report.
** Trees Outside Woods https://www.woodlandtrust.org.uk/media/1821/trees-outside-woods-ecological-value.pdf
Further reading about Hedges and Hedges
Hedgelink UK http://www.hedgelink.org.uk/index.php?page=16
Devon Hedge Group http://www.devon.gov.uk/devon_hedges
Blackdown Hills Hedge Association http://bhha.info/
Natural England http://www.cfeonline.org.uk/hedge-trees/
We have started planting the Devon Whitebeams paid for with a grant from East Devon AONB. The first three saplings were planted at the top of the Delderfield Nature Reserve on Peak Hill.The south west of England has a number distinct Whitebeam species. Genetic research by Tracey Hamston at Exeter University has shown that most them began as hybrids between the Wild Service Tree and another Sorbus species, probably the Common Whitebeam. These include the Bloody Whitebeam (Sorbus vexans) with its deep red berries, and the No Parking Whitebeam (Sorbus admonitor). So named because the first specimen identified was at Watersmeet, Exmoor, and it had a no parking sign attached to it.Most of these species are threatened because of habitat loss. Apart from valuing biodiversity for its own sake, one important reason that we keep them alive is that new hybrids may arise and these will be able to adapt to our changing climate. Apart from the location specific name, Devon Whitebeam has been chosen for our project because it is probably the most adaptable species and can thrive away from its original sites between Exmoor and Dartmoor.You can find out more at https://www.botanic.cam.ac.uk/the-garden/horticultural-collections/research-collections/native-sorbus/
FREE TREES SUCCESS
A big thank you to The Woodland Trust and Devon Wildlife Trust who supplied the 300 free trees for today’s event. Also we are very grateful to the staff at King’s Garden Centre for allowing us to use their premises, and for organising the car parking as so many people turned up. The biggest thank you has to go to you, members of the public of Sidmouth who have taken on the trees to grow in your gardens, the valley will be a better place because of your efforts. We are sorry that demand out-stripped supply, if you missed out, DWT are running several more events around Devon, the next one is at Seaton Jurassic next Tuesday, details are on their website https://www.devonwildlifetrust.org/what-we-do/our-projects/saving-devons-treescapes