On the last day of November, the decadence of summer is long gone. The flowers and leaves, butterflies and bees were so easy to take for granted until autumn and then winter take them from us. But every season has its own treasures and the wind-whipped, leaf-stripped trees are on glorious display across the countryside.
One thought which always strikes me when I see winter silhouettes, is how amazingly adept trees are at achieving their structure in an infinite number of ways. A line of trees planted together will each grow to maturity in a different form. The form will be dictated by species, by sub-species perhaps, by individual genetic variation, phenotypic plasticity to adapt to the conditions, defense responses to biotic attack or abiotic damage such as frost and wind, competition avoidance strategies and more besides. There are as many answers as there are trees to the simple question of how to be upright. And whilst the tree is growing, the process is never complete as the tree grows adaptively to maintain its balance and posture with continual interaction with their environment.
One recent 2015 study put an estimate of 3 trillion on the number of trees in the world. The mind boggles to even begin to comprehend the variety and scale which this number encompasses, but here are nine examples from my walk near Muston Meadows at dusk this evening.
I noticed that the buds of the hawthorn at the back of my garden are starting to break – always an early starter but a good omen of spring just around the corner. With the return of the leaves to the trees, now is a good time to familiarise yourself with the symptoms of ash dieback ready for the spring as it could well be that 2013 is the year that this disease is really going to take hold in the UK. With so many trees in so many locations across the country, the best chance for monitoring the spread is for people who walk, work and live in the countryside to be vigilant. There are a number of locations in East Anglia where the disease is confirmed which makes the risk of cases around Grantham a real possibility.
Ash is a widespread species in the UK – as an ecological surveyor I have been to many sites in the east midlands and beyond and it is very rare that any broad leaf woodland doesn’t have a component of ash – it is the third most common UK tree species.
Ash is the first species I learnt to ID in the winter as it really is so distinctive, the buds are jet black and triangular in shape. The bark is smooth and ash (!) gray in colour. The leaves are pinnate – that is the leaflets come off a central stem in pairs.
You come across large impressive old trees within hedgerows and older woodlands, they also have a strong presence within secondary woodlands where they can be the dominant tree – there are some good examples of this type of woodland just down the road in Oakham. You can also come across them invading fields in the first wave of succession from grassland to woodland, here they grow as single stems, “whips”, a very appropriate name if one snaps back and cracks you across the leg! It is therefore quite diverse tree – they can be a constituent of a climax community, they grow quickly enough to gain dominance within a woodland after only 50 years or so, but they can also be the first woody species to stake its claim on a woodland-to-be.
Ash trees are prevalent in and around Grantham, older specimens can be found in Belton House and around the town close to the river, whilst newer specimens form part of the planting at the Woodland Trust’s Londonthorpe Woods.
Chalara fraxinea (the second part of the latin relating to the ash genus – Fraxinus) is the fungus which causes ash dieback. It is thought to have come from nursery stock brought across from the Netherlands, a location which instantly brings to mind the Dutch elm disease which decimated the English elm in the middle of the last century. It spreads by spores which are tiny airborne particles which means that it is easily spread by the wind within a certain radius, up to around 10 miles. Over longer distances, it is thought that the movement of diseased material such as nursery trees is likely to be the main cause which is why import and movement was banned in the UK at the end of October in 2012.
The disease can be detected even now, in the winter and spring, but becomes more obvious when the trees come out of dormancy and the leaves are in evidence. The Forestry Commission has a very thorough guide on how to recognise which I would urge everybody to read so that you know the symptoms. There are other diseases, pathogens, fungi and environmental impacts which can cause an ash tree to be in poor condition – this guide should help you to spot the distinctive signs of this particular disease.
The Dutch Elm epidemic in the 1970’s did not kill every elm tree and a small number still stand around the country – only a tiny fraction. It is assumed that these trees have immunity to the disease and, on this basis, The Conservation Foundation has begun a project of collecting cuttings from these trees, propagating them and distributing them to schools and other locations all around the country. This was begun in 2009 so it is too soon yet to know whether this is to be a success but, because the cutting method ensures that the derived seedlings are clones of the original tree, there is every reason to think it will be and hopefully, one day, English elm will be a common sight in our countryside once more.
Based on the existence of some similarly disease resistant trees in Denmark, there is a NERC funded project currently under way to sequence the ash genome and try to identify the genetic basis for immunity. This would put us in a position where the lost ash trees (and it is almost inevitable that at least a proportion will be lost) can be replaced with disease resistant trees. The strong hope is that these resistant trees will be identified in the UK so that any replacement planting programme will not require stock from abroad but will remain of British origin.
What can you do to help?
Familiarise yourself with the symptoms of ash dieback here or watch the Forestry Commission produced video so that you know what to look for when out and about;
Report any findings, or suspicions of chalara to the Forestry Commission using their Tree Alert form here – they will want to know the exact location of the tree, the symptoms noted and any other information which will help them to find it. Photographs are also very useful and there is a chance to upload these;
Install the Tree Alert app on your phone to issue reports when you’re out and about – link here for android or iOS