Lower Wood: the changing face of an ancient woodland

Fresh snow in Lower Wood, Ashwellthorpe, February 2012. Photo by S. Shailes. CC BY 4.0

Fresh snow in Lower Wood, Ashwellthorpe, February 2012. Photo by S. Shailes. CC BY 4.0

Lower Wood in Ashwellthorpe is one of the few remaining ancient woodlands in Norfolk. Today, the wood is about 100 acres in size, which is only a small remnant of its recorded size in the Domesday Book of 1086. Having been managed for centuries to produce wood for local industry, the last 50 years have seen the wood undergo many changes and face new challenges.

The wood was managed by coppicing to produce wood for a variety of purposes including charcoal production, fencing and furniture. It also supplied the local brush-making industry, which by the end of the 1700s was thriving in Norfolk (1). From 1922, the wood supplied the Co-operative Wholesale Society Brushworks in the nearby town of Wymondham, which in its heyday employed over 200 people. However, by 1983, the brushworks was unable to compete with cheap imports from abroad and it closed (1). Coppicing stopped in Lower Wood sometime in the 1970s and without it, the canopy of the wood became denser and biodiversity suffered as less shade tolerant plant species struggled to survive.

In 1973, Lower Wood was given a Site of Special Scientific Interest (SSSI) notification (2) because it is an ancient woodland where most of the coppice trees are plateau-alder (Alnus glutinosa), which is rare in the UK. Other tree species include hazel (Corylus avellana), field maple (Acer campestre) and sallow (Salix caprea). It was traditional to leave some trees in a coppice uncut for longer periods to produce wood with a larger diameter (called timber) to use for building or shipbuilding and, in Lower Wood, these so-called “standards” are mostly oak (Quercus robur), ash (Fraxinus excelsior) and hornbeam (Carpinus betula).

Early purple orchids growing near a coppice stool (top left). Common twayblade in flower (bottom left). A white admiral butterfly (right). Photos taken in Lower Wood by Anne Edwards.

Early purple orchids growing near a coppice stool (top left). Herb paris in flower (bottom left). A white admiral butterfly (right). Photos taken in Lower Wood by Anne Edwards.

The wood is also unusual in that it lies on a boulder clay plateau and the chalk in the clay promotes very diverse ground plants including uncommon species such as ramsons (Allium ursinum), early purple orchid (Orchis mascula), herb paris (Paris quadrifolia) and common twayblade (Listera ovate) (2). The plants in turn support interesting wildlife and the site is home to the rare white admiral butterfly (Limenitis camilla), which exclusively lays its eggs in honeysuckle (Lonicera periclymenum), a climbing vine-like plant.

Despite becoming a SSSI, the wood was neglected until the Norfolk Wildlife Trust (NWT) purchased it and started restoration coppicing in 1992. The first round of coppicing was especially tough because, due to the long gap in management, the trees had produced wood that was much larger in diameter than would be produced from a normal coppice cycle. The NWT coppice the wood to conserve it, not for the wood it produces, so the cutting season is restricted to October-March to prevent trampling of wildflowers or disturbing bird nests. Also, some of the cut wood is left to decompose to support fungi and insects. Newly coppiced areas are surrounded by electric fences for the first few years after cutting as they are very vulnerable to damage by grazing deer. This is becoming an increasing problem in the UK as deer numbers rise to due to the lack of natural predators.

By 2012, a regular coppice rotation of about 14 years had been established and the woodland was recovering. However, in the Autumn, there was some alarming news: ash dieback disease had been spotted in the wood, the first recorded outbreak in the UK that was not linked to imported saplings in a plant nursery. Ash dieback is caused by a fungus called Hymenoscyphus pseudoalbidus (also known as Chalara fraxinea). There is no treatment for the disease, which eventually kills the host tree, and since then it has spread across the country.

Young tree infected with the fungus. A small necrotic (dead tissue) spot is visible on the stem

Young tree infected with the fungus Hymenoscyphus pseudoalbidus. A necrotic (dead tissue) spot is visible on the stem. Photo credit: Anne Edwards

In Lower Wood, the disease has spread very quickly. Anne Edwards, who leads a group of coppicing volunteers in the wood said: “many of the coppiced ash and seedlings have died already. Several of the standards are also show clear signs of the disease.”

The death of ash trees in the wood is leaving gaps in the canopy, so how will this affect the rest of the flora? Anne says: “bramble will probably run rampant. There are signs of other tree seedlings coming through in the [coppice] block we are [working] in now: hornbeam—quite slow growing so usually out competed by ash seedlings—spindle, hawthorn, field maple. We are “layering” hazel shoots into areas where the ash coppice has died to try and fill in the gaps. If we can keep the deer out, the mixed tree seedlings and hazel might stand a chance.”

There is hope that at least some of the ash trees will survive the disease and the woodland will recover in time. “The [ash] coppice does seem to be showing a range of sensitivities to the fungus, so in some trunks the fungus seems to move very rapidly, in others, progress is much slower. We have tagged any that, at this early stage, appear to show some tolerance.”

Since Lower wood contains trees of many species, ash dieback disease will not destroy the woodland, but it is dramatically altering the mix of trees found there. It is not yet clear what impact this will have on the other plants and wildlife in the wood in the long term, only time will tell.

For more information about ash dieback disease and some of the research that is underway to understand more about the disease please follow these links:

OpenAshDieback: A hub for crowdsourcing information and genomic resources for Ash Dieback

Nornex: a network of scientists from eleven research institutions aiming to make tools to help understand how to deal with ash dieback

AshTag: you can help to identify diseased trees and monitor their health.

Read more articles about woodlands in Focus on… Woodlands:past, present and future

Author’s note: It does not snow in Norfolk often, so the photo at the top of the article is not an accurate reflection of what the wood usually looks like in winter. However, I decided to include it  because it was taken on one of my favourite visits to the wood (and it is almost Christmas!)

References:

  1. Manning, I.M. (1983) The Co-operative Wholesale Society Brushworks, Wymondham Journal of Norfolk Industrial Archaeology Society Vol. 3 (1981-85) p 169.2
  2. SSSI notification: Lower Wood, Ashwellthorpe (1973, 1983)

Seeds: up close and personal

seed of purple owl’s foot clover (Castilleja exserta subsp. latifolia) Image credit: see below

Seed of the purple owl’s foot clover with its honeycomb seadcoat shown in pink (Castilleja exserta subsp. latifolia) Image credit: Stuppy, Kesseler and Harley.

Seeds are the plant equivalent of an armoured vehicle. They carry the offspring of plants out into the dangerous world and protect them until the time is right for them to grow into new plants. There is huge variety in the size and shapes of seeds, ranging from tiny orchid seeds weighing only 1-10 μg to the enormous seeds of the Seychelles nut that weigh 20 kg.

The amazing variety in seeds is explored in the book Wonders of the Plant Kingdom: a Microcosm Revealed. The book is the result of a collaboration between two botanists—Wolfgang Stuppy and Madeline Harley—and the artist Rob Kesseler. Most of the images in the book have been taken using an electron microscope, which provides a higher level of magnification than traditional light microscopy. These images were originally in black-and-white, but Kesseler has skillfully added colour to help bring them to life. Continue reading

Book Review: The End of Plagues – John Rhodes

I originally posted this review in the summer on the Book Reviews page but I am reposting it now as I think it–or one of the other books I have read recently–would make a good Christmas present.

end-plagues-global-battle-against-infectious-disease-john-rhodes-hardcover-cover-artIn The End of Plagues, John Rhodes guides the reader through the history of fighting infectious diseases. Much of the book focusses on story of Edward Jenner who developed the first vaccine to immunise people against smallpox in 1796. The global fight against smallpox to its eradication in the 1970’s is a fascinating tale played out over several hundred years with many impressive feats. John Rhodes telling of the story introduces the reader to the people involved and provides biological explanations along the way. The book also covers the successes, difficulties and controversies in producing vaccines for other infectious diseases including polio, tuberculosis, whooping cough and flu.

I would highly recommend this book to anyone with an interest in the history of medicine. For a more in depth review follow this link.

Why is my orange green?

While in The Gambia I ate some oranges with green skins. I was surprised when I first saw them because I had always assumed that oranges are orange. In the English language, the colour orange was even named after the fruit. So why are the skins of some oranges green?

Oranges grown in The Gambia and other tropical countries have green skin. Image Credit: Louise Tutton

Oranges grown in The Gambia and other tropical countries have green skin. Image Credit: Louise Tutton

Oranges and other citrus fruits—e.g. lemons, limes and grapefruits—have been cultivated for a long time. The sweet orange (Citrus sinensis)—the most commonly variety we eat or make into juice—does not exist in the wild but is actually a hybrid of tangerines and the pomelo or “Chinese grapefruit” from South-East Asia. Continue reading

Book review: The Compatibility Gene by Daniel M. Davis

compatbility geneIn The Compatibility Gene, Daniel M. Davis takes us through some of the major discoveries that have helped us to understand how our immune system can target invaders while leaving our own cells alone. The way the immune system identifies “self” and “non-self” has important implications for fighting disease, transplant success and other aspects of life including brain function and pregnancy. Davis focusses on the MHC genes–which that code for proteins that sit on the surface of our cells and interact with white blood cells–and features the personal stories of some of the scientists who have studied them.

For me, this book was a reminder of some of the stuff I learnt about the immune system as an undergraduate student, but it also took me into new territory, including our emerging understanding of the role of the MHC genes in brain function and pregnancy. I would highly recommend this book to anyone with an interest in human biology.

For an in-depth review please follow this link.

 

When is a fungus not a fungus? When it is an oomycete…

If I asked you to name a microbe that can cause disease in plants you are likely to name a species of bacteria, fungus or virus. But would you name an oomycete?

An A. thaliana leaf infected with downy mildew. The oomycete H. arabidopsidis is shown in blue. Image by Caillaud et al. (2014) licenced under CC-BY.

An A. thaliana leaf infected with downy mildew. The oomycete H. arabidopsidis is shown in blue. Image by Caillaud et al. (2014) licenced under CC-BY.

At first glance oomycetes look quite like fungi because they grow by producing branching filaments—similar to fungal mycelia—through which they absorb nutrients from their surroundings. Oomycetes used to be classified as fungi but, in fact, they are not closely related.

The cell wall that surrounds oomycete cells provides a clue of where they fit in the tree of life: it is made of cellulose, not chitin like fungi, suggesting that oomycetes are more closely-related to algae or plants. This is supported by other features of the lifestyle of oomcyetes and analyses of their genetic information, which place them in the same Phylum as brown algae and diatoms (1). Continue reading

Book review: Cells to Civilizations by Enrico Coen

cells to civilisationsIn Cells to Civilizations: The Principles of Change that Shape Life, Coen presents evolution, development, learning and culture as transformational processes that share seven fundamental principles. To start with it felt strange to read about familiar concepts in terms of Coen’s seven principles, but I liked how it made me think about the processes in a different way. I enjoyed Coen’s explanations of his processes and the diagrams were clear and very useful. However, while it was clear why it can be useful to think about evolution, development and learning using a set of shared principles, I wasn’t quite so convinced of the relevance of thinking about cultural transformations in the same terms as the biological processes. With famous works of art featuring in many of Coen’s explanations throughout the book, the book is an unusual, but quite interesting mix of science, philosophy and art.

All in all, I enjoyed reading this book and would recommend it to anyone with an interest in evolution, development and learning. To get the most out of the diagrams in the book I would suggest reading a print copy as I found referring to diagrams on my kindle a bit cumbersome. For a more in depth review follow this link.