Plants more resilient than animals through mass extinctions

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By Nicola Temple

The fossil record suggests that a diversity of land plants had evolved by about 472 million years ago (mya). There is evidence to suggest that plants made the move onto land as much as 700 mya [1], placing them in the midst of the five largest extinction events to have shaped life on our planet.

Researchers from the University of Gothenburg released a study earlier this year showing that plants have generally been more resilient to these extinction events than animals. They looked at more than 20,000 plant fossils to see how these mass extinction events affected plant diversity [2].

Ferns and horsetails dominated the
landscape by the end of the Devonian.
Credit: Nicola Temple

They found, not unexpectedly, that each group of plants fared differently through each extinction event – with some doing better than others. Though plants might experience mass extinctions, the researchers concluded that plants also began to diversify again quickly after such events, so that more new species were being generated than were being lost.

“In the plant kingdom, mass extinction events can be seen as opportunities for turnover leading to renewed biodiversity,” said leading author Daniele Silvestro.

The big five

Scientists have identified five mass extinction events since land plants have evolved.

Ordovician – Silurian mass extinction (approximately 443 mya): This event wiped out approximately 85% of sea-dwelling creatures, such as trilobites. It has been hypothesised that a huge ice sheet in the southern hemisphere led to the alteration of climate patterns, a drop in the sea-level and a change in ocean chemistry.

Late Devonian (approximately 359 mya): This event is likely a series of smaller extinction events that happened over several million years, but the end result was a loss of 75% of all species on Earth. Changes in sea level, multiple asteroid impacts and new plants that were changing the soil chemistry have all been attributed to this period of extinction.

Permian (approximately 248 mya): It is estimated that 96% of all species were wiped out during this mass extinction. Marine creatures were badly affected and it is the only extinction thought to have had an impact on insects. Hypotheses as to what led to the demise of so many creatures have included combinations of asteroid impacts, volcanic activity, methane releases and decreased oxygen levels.

Triassic – Jurassic (approximately 200 mya): A mere fifty million years after the Permian extinction, about fifty percent of life was wiped out again. Plants seem to have been largely unaffected by this extinction event, but many of the marine reptiles were lost as well as large amphibians and cephalopod molluscs. Large scale volcanic activity and asteroid impacts have both been credited for these extinctions.

This dinosaur can still be spotted in the Evolutionary Dell
at the Botanic Garden! Credit: Nicola Temple

Cretaceous – Paleogene (approximately 65 mya): This extinction event is well known for the loss of the dinosaurs, pterosaurs and ammonites. The prevailing theory for this extinction is the impact of a large asteroid off the coast of Yucatán, Mexico and the subsequent fall-out effects.

While each of these mass extinction events meant the widespread loss of species, they also opened up opportunities for diversification and new species. Had the dinosaurs not gone extinct, for example, mammals would likely not have diversified, compromising our own lineage as humans. Flowering plants experienced extensive diversification after the Cretaceous – Paleogene event and they remain a dominant group today.

The key to resistence might be in duplicate DNA

The Wollemi Pine (Wollemia nobilis)
on display at the Botanic Garden has fossils
dating back 200 million years.
Credit: Nicola Temple

The majority of plants have undergone one or more duplication events where an exact copy of their entire genome is created. This is known as polyploidy – multiple copies of the same genome. Bread wheat, as an example, is hexaploid as it has six sets of chromosomes. Research has shown that one of these doubling events coincides with the Cretaceous – Paleogene mass extinction, approximately 65 million years ago[3].

An extra set of chromosomes could be quite convenient during a prolonged period of stress, such as a massive asteroid strike and its subsequent effects.  Polyploids might be better equipped to resist harmful mutations or perhaps take on mutations that offer a selective advantage under new conditions. Polyploidy plants also tend to be self-fertilising or asexual reproducers, which would be another advantage at a time when finding a partner for breeding could be limited.

Looking forward to a time of inevitable change

The theory that polyploidy confers an advantage during times of change can be witnessed in today’s extreme environments. There is evidence from the Arctic that polyploid plants are more successful than diploid plants at colonising habitats left by receding glaciers [3].

The Evolution of Land Plants Display at the Botanic Garden
(wrapped up for winter) is a walk through time.
Credit: Nicola Temple

Looking into extreme and changing habitats, such as the Arctic, as well as back into the fossil record can give us some indications of which plant groups may be more resilient to the changing climate we are currently experiencing.

You can take a walk through time in the University of Bristol Botanic Garden’s Evolution of Land Plants Display. There you will see living representatives from the groups of land plants that lived from the Cambrian to the Cretaceous, including unusual plants like Wollemi Pine (Wollemia nobilis) with fossils dating back 200 million years.

References:

[1] ‘First land plants and fungi changed Earth’s climate, paving the way for explosive evolution of land animals, new gene study suggests’, Penn State Science < http://science.psu.edu/news-and-events/2001-news/Hedges8-2001.htm>
[2] Silvestro D, Cascales-Miñana B, Bacon CD, Antonelli A (2015). Revisiting the origin and diversification of vascular plants through a comprehensive Bayesian analysis of the fossil record. New Phytologist (in press).
[3] Yong E (23 Mar 2009) ‘Extra genomes helped plants to survive extinction event that killed dinosaurs’, Not Exactly Rocket Science [blog] <http://scienceblogs.com/notrocketscience/2009/03/23/extra-genomes-helped-plants-to-survive-extinction-event-that/>

Local limestone quarry receives a special collection of plants from the University of Bristol Botanic Garden

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By Helen Roberts


It’s a bitterly cold February morning and I’ve driven to the outskirts of the small village of Wick in South Gloucestershire to meet with Roland de Hauke. Roland is going to give me a tour of Wick Quarry and the local nature reserve. It is extremely claggy underfoot and parts of the road are submerged underwater, so I am extremely relieved when Roland shows me to his 4 x 4 vehicle in order to tour the vast 100-acre site.
First view of Wick Quarry. Credit: Helen Roberts.

Roland, a passionate botanist and conservationist, bought the quarry and nature reserve two years ago with the aim of restoring it with a mosaic of habitats to maximise biodiversity.
“I have always been interested in botany and conservation and I am fascinated by trees,” remarks Roland, “and I am particularly keen to introduce species of local provenance. In the past, a lot of quarry restoration has involved a broad-brush approach, with a view that what works well on one particular site will work for other sites too. This just simply isn’t the case and I want to change that perception.”
The quarry’s situation is extremely impressive with sheer rocky cliffs of loose exposed limestone and a huge quarry lake approximately 60 metres deep. It borders with the Wick Golden Valley Local Nature Reserve (also owned by Roland), which has locally important plants, including Viper’s Bugloss and Spleenwort, and wildlife, including a dozen or so different species of bats.  The reserve’s interesting geology has also earned it the designation of Regionally ImportantGeological and Geomorphological Site – with its excellent examples of stratification. The reserve is also part of a larger Site of Nature Conservation Interest called the ‘Wick Rocks and River Boyd’.
A second quarry lake where it is hoped floating reed beds 
will be established. Credit: Helen Roberts.

I was impressed by the quarry and as a landscape architect this was probably one of the most interesting sites I’d visited in terms of visual impact and biodiversity potential. I could imagine the site in 25 to 50 years time as a vital stepping-stone for local habitats as our landscape becomes further fragmented by development.

Propagating rare and endemic species

Within the University of Bristol Botanic Garden’s local plant collection are some special trees within the Sorbus genus, which are more commonly known as whitebeams, rowans and wild service trees. Two species, Bristol whitebeam (Sorbus bristoliensis) and Wilmott’s whitebeam (Sorbus wilmottiana), grow only in the region of the Avon Gorge.
The location of some of the plants donated by the
University of Bristol Botanic Garden. Credit: Helen Roberts.

The Garden maintains these rare endemic species within its collection as part of the ‘Global Strategy for Plant Conservation’. Threatened plant species are kept in ex situcollections so that they are available for recovery and restoration programmes.

The Botanic Garden has donated a number of Sorbus species to Roland in the hope that they may get established within his quarry and become a self supporting population, including S. aria, S. bristoliensis, S. eminens, S. anglica, and S. porrigentiformis. Both the Director of the Garden, Professor Simon Hiscock, and the Curator, Nick Wray, have given Roland advice on planting and species introduction. The donated plants were all propagated from wild plants in the Avon Gorge and Leigh Woods between 1996 and 1997 by the Garden staff.
“Actually, planting the donated plants has been an interesting and exciting task as accessibility is an issue and the rock faces are fairly steep and loose in places”, explains Roland.
Creating wetlands
The lake itself is problematic because its steep sides do not lend themselves to wetland creation; this is where Roland is concentrating his efforts over the next 5 years or so. He will make shallower shelved areas into the water with the idea of creating floating reed bed habitats, which will be planted in the spring. These reed bed habitats can support invertebrates and fish, which are food resources that will attract wetland birds.
Sheer quarry sides descend into the lake.
Credit: Helen Roberts.

“At the moment we are not seeing a lot of wetland birds using the quarry lakes for any long periods of time as there just isn’t the food available for them”, explains Roland. “After about a day or two, the water birds simply move on to find a better food resource and that’s where reed beds will provide a suitable habitat for [them] to stay for longer.”

The future of the quarry
Roland is also looking to develop huge areas of species-rich grassland and is seeking advice on species that will attract a diversity of invertebrates.
The site will likely be closed to the general public in order to reduce the disturbance by humans.  However, it will be open to specialist interest groups, including local schools, to help educate local communities about the importance of rare local species, illustrate effective quarry restoration and allow the long term monitoring and management of the site.
“This is a long term project that I’m really excited about and at public consultation meetings most people there have been genuinely excited about it too,” commented Roland. “I am very grateful to the University of Bristol Botanic Garden for the donated plants and look forward to working with them in future.”

Mud, glorious mud

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By Jacqueline Campbell

Connections are often established in the most unexpected manner. How many times do you come away from a situation thinking “it’s a small world”, where just the opportune mention of a single word or phrase strikes a chord and is enough to foster new links and an avenue by which to share new ideas.
As unlikely as it seems, the words “pond mud” brought the Red Maids’ Schooltogether with the University of Bristol Botanic Garden recently. And from this link, students at the school have gone on to create their own miniature sustainable ecosystems using mud gathered from the garden’s mature and established ponds.

Marvellous muddy mesocosms

Mrs Turner, Head of Biology at Red Maids’ School, studying
the mesocosms.
Sixth Form students following the International Baccalaureate biology curriculum are required to complete a number of practical experiments. One of these is the creation of a mesocosm known as a Winogradsky column; essentially a self-contained, sustainable ecosystem grown in a sealed plastic bottle under controlled conditions.
A critical element of this experiment is pond mud. As they are situated no more than a couple of miles apart, the Red Maids’ School approached staff at the Botanic Garden for their advice and assistance in setting up such an ecosystem.  A number of phone calls and a few visits later, two groups of students have used pond mud sourced from the Botanic Garden and are watching to see the bacteria in their stratified ecosystems develop. 
The mesocosms in this image are just a few hours old.
Images are taken every two days to track and record the changes
over time.
The mesocoms now live on a sunny window sill in the Biology Department at Red Maids’, and are a constant source of curiosity to all. Despite a little reluctance mainly associated with the smell of pond mud, the students involved are thrilled to have created their own ecosystems and are often now found enthusing about the colour of their bacteria and amount of respiration they can see.
Images taken every two days are providing a good record of how the ecosystems are developing over time. From an initial cloudy but uniform situation, clearly defined layers are forming coupled with a notable increase in the pressure within the bottles showing the incredible amount of respiration that is occurring within the system.

Bacteria of many colours

Students have seen the pressure within their ecosystems
increase over time thanks to the highly visible levels of
respiration occurring within the sealed environment. A range
of different coloured bacteria are also now present.
The ingredients required to create the Winogradsky column are: pond mud, shredded newspaper, crushed egg shells and raw egg yolk. Pond mud provides a suitable base while the newspaper, egg shell and egg yolk provide sources of carbon, carbon dioxide and sulphur respectively. As a first step, these components are mixed together and poured into the bottom of a plastic fizzy drinks bottle.
On top of this layer comes another of compost, followed finally by some pond water. The idea is that many different coloured layers of bacteria develop, and each of these transforms molecules for the others to use. And as long as there is light entering the system, the column should theoretically continue to maintain a healthy microbial ecosystem for many months.
Waiting to develop: Over time, students at Red Maids’ hope
to see their Winogradsky columns develop into a stratified
system. This will provide a visual example of various modes of
metabolism and zonation in the microbial world. The
mesocosm shown in this image is several months old. 
Conditions at the bottom of the column are highly anaerobic with a high sulphide concentration ideal for the growth of sulphate reducing bacteria, green sulphur bacteria and purple sulphur bacteria. Moving higher in the column, with conditions becoming more aerobic and a reduction in sulphide concentration, we can expect to see the development of purple non-sulphur bacteria, iron-oxidizing bacteria, heterotrophic bacteria and cyanobacteria. 
Of course none of this would be possible without the kind assistance of the Botanic Garden staff, who waded into freezing winter waters to collect the mud. The Red Maids’ School is very grateful to have established this connection, and hopes that it too will blossom over time. 

Dr Jacqueline Campbell has a PhD in physics from St Andrews University and twelve years of editorial experience working for the Institute of Physics Publishing and as a freelance journalist. She now works as a science technician at the Red Maids’ School.

Some like it hot

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By Helen Roberts

With the dismal wet wintry weather prevailing in the UK at this time of year, most people look forward to the return of warm long days, evenings outside and picnics on the beach. Things can look a little dreary and dull in people’s gardens at the moment, before the arrival of spring and its profusion of bulbs and other spring flowers. The Mediterranean collection at the University of Bristol Botanic Gardens helps to remind me of summer sun and balmy places.

Maquis: scrubland vegetation of the Mediterranean

Maquis shrubland in Conca de Dalt of Catalonia, northeastern Spain.
Photo by Gustau Erill i Pinyot.
Licensed under CC BY-SA 3.0 via Wikimedia Commons 
The Mediterranean Basin of Europe and North Africa display shows examples from different vegetation biomes; the collection includes evergreen forest, maquis or macchie and garique. Many of the highly aromatic and fragrant plants are associated with maquis vegetation. The maquis biome, which often includes leathery broadleaves, evergreen shrubs and small trees, usually occurs on the lower slopes of mountains bordering the Mediterranean Sea.
The climate of the maquis biome is characterised by long dry summers and short mild wet winters, with low annual rainfall. Ocean currents and fog influence the temperature and limit the growing season. The plants that grow here cope with the very hot summers by entering a slow growth period or dormant phase so they can resist long periods of drought.
Plant defences in this harsh environment are numerous. Many shrubs and low growing vegetation have thick tough leathery leaves, which reduce water loss but also deter hungry herbivores from grazing. Many plants contain volatile organic compounds (VOCs). These chemicals help facilitate interactions between plants and the environment – from attracting pollinators and seed dispensers to warding off pathogens, parasites and herbivores. When a plant is under attack from a herbivore, for example, it will release a chemical cocktail of VOCs, some of which have been found to attract natural predators of the herbivores. VOCs are also good at leaching into surrounding soil and so will deter the growth of other plants.
Plants containing VOCs are often very flammable, which is partly why areas of maquis are prone to wild fires.

Pyrophytes need a little fire in their lifecycle

Montpelier cistus (Cistus monspeliensis).
Photo by Jean-Pol GRANDMONT
via Wikimedia Commons
Many of the plants in the maquis biomes are pyrophytes (fire loving plants) and require wild fires for reproduction, recycling of nutrients and removal of dead vegetation. Pyrophytes can be classed as active or passive. Active pyrophytes actually encourage fires as they often require fire in order to reproduce. Passive pyrophytes resist the effects of fires.
An active pyrophyte growing in the University of Bristol Botanic Garden maquis biome is Cistus monspeliensis, commonly known as the Montpelier cistus or rock rose. When a fire starts, Cistushas evolved to burn. This combustible conclusion to the adult plant helps destroy competing plants near to it. However, unlike its competitors, the fire will mechanically rupture the seeds of Cistus and the smoke and heat will trigger germination of the next generation. The Cistus seedlings have the advantage of beginning life in a competitor-free environment.
A closed cone and foliage of Pinus pinea.
 Licensed under CC BY-SA 2.5 es via Wikimedia Commons 
Pinus pinea (the stone pine) is also in the Botanic Garden’s collection and it is a passive pyrophyte. It has a thick bark with high moisture content to help it resist fire. Its hard-coated fire resistant cones open when exposed to high temperatures. This is particularly useful in the harvest of the desirable seeds, known to many of us as pine nuts. As the tree grows, it self-prunes the lower branches, which helps prevent the fire travelling at ground level from jumping up into the canopy and potentially destroying the tree.
Some species spring back from fire events by sprouting new growth from the old. There are two such sprouter species in the Botanic Garden’s collection. The carob tree (Ceratonia siliqua) re-sprouts from epicormicbuds that lie dormant beneath the bark. These buds are normally suppressed by hormones produced by active shoots, but after a fire event and the destruction of the foliage, the buds are activated. Erica arborea (tree heath) re-sprouts from root crowns so is known as a below ground sprouter. It produces seed in the first post-fire summer.
Fire adapted plants of the maquis biome are only a handful of those plants making up the Garden’s Mediterranean collection. The collection also includes plants (some of which are also pyrophytes) from the southwestern tip of South Africa and displays are also under development from the Western andSouthern Australian, Chilean and Californian Mediterranean climate regions.
The half hardy plants of the Mediterranean collection are planted out in each respective biome in the summer, whilst more tender plants are protected from our cooler Bristol temperatures in the warm temperate and cool zones of the glasshouses. The outdoor collection sits on a south facing rocky bank to maximise the amount of sun and aid drainage. The path meanders through the collection allowing visitors to appreciate the appearance and fragrances of the different plants. These are all good things to look forward to in the summer months, but meanwhile if you have the chance to warm yourself in front of a crackling fire, think of those volatile fire-loving plants! 

A walk through the mendips

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By Helen Roberts

A few weeks ago our family, had a great day out walking on the Mendip Hills. We set off in autumn sunshine, through pretty deciduous woodland, to an Iron Age hill fort called Dolebury Warren – an upland area of calcareous grassland. Having lived on the edge of the Mendips during my childhood, I am always keen to show my children where I used to explore as a youngster.
Part of Cheddar Gorge, Somerset, England, seen from a
light aircraft. Photo by Adrian Pingstone (1975).
The Mendips are a range of mainly carboniferous limestone hills comprised of at least four convex fold structures formed between 363 and 325 million years ago, during the end of the Carboniferous Period. Weathering of the limestone has resulted in features including gorges, dry valleys, screes and swallets (sink-holes) and incorporates the famous Cheddar Gorge and Burrington Combe, each with extensive cave systems. The area also has interesting landscape characteristics like limestone pavements and other karst structures.
The geology of the Mendips makes for interesting ecological communities and consists of large areas of open calcareous grassland with many rare flowering plants. For instance, Dolebury Warren owned by the National Trust and managed by Avon Wildlife Trust, sits within the Mendip Hills Area of Outstanding Natural Beauty and is a Site of Special Scientific Interest due to its important limestone flower communities. These flower communities attract up to 70% of all British butterfly species. Dolebury Warren has a gradation of communities from species rich calcareous grassland, through acid grassland to limestone heathland, with large areas of mixed scrub.
Cheddar Pink (Dianthus gratianopolitanus).
Photo by Paul Harvey, via Wikimedia Commons
The charity Plantlife has identified the Mendips as an Important Plant Area (IPA), which is an area of landscape that has very high botanical importance. Some plant species found on the Mendips are found nowhere else. Due to factors such as over grazing, poor land management, scrub encroachment and agricultural intensification, these plants are declining in numbers and some are threatened with extinction. The University of Bristol Botanic Gardenhas a local flora and rare native plant collection, which includes a sub-collection from the Mendip Hills, Limestone Cliffs and Coastal Islands. The collection was developed to help grow and interpret some of the rare and threatened plant species found in these habitats. The collection represents an important habitat and phytogeographic display and is helping meet the objectives of the ‘Global Strategy forPlant Conservation’.

Rare plants of the Mendips 


One of the Mendip plants in the Botanic Garden’s collection is the Cheddar Pink (Dianthus gratianopolitanus). This is a very pretty scented pink flower that grows in a few places on the Mendips but mostly at the original site of Cheddar Gorge. This plant was originally discovered about 300 years ago and is considered the pride of Somerset and was voted the County Flower. It grows best in rock crevices, high on the limestone crags of the Gorge, and can be seen in June and July using binoculars to search patches of colour visible on the cliffs, just above the road.
Also growing at the Gardens is the interestingly named Starved Sedge (Carex depauperata). This is an exceptionally endangered plant that is only found in one local area – in the woods and on a hedge bank near the small town of Axbridge. This is one of only two sites in the whole of the UK. Fifteen years ago, Starved Sedge had declined to such an extent that there was only one plant in the whole of Britain. As appearances go, it’s not much to look at. It’s a tussocky plant with trailing leaves and gigantic seeds and can easily be mistaken for some common woodland grasses. A reintroduction programme has improved the status of this plant by using cuttings and seed collecting to re-establish it at other sites in the UK.
The University Botanic Garden are also helping to preserve another plant at high risk of extinction and classed as nationally rare, known as Somerset Hair-grass (Koeleria vallesiana). Again, this is a fairly innocuous grass restricted to the Mendip Hills with very slow spreading habit. The Bristol Botanic Garden’s specimens were collected from Brean Down, which is the most westerly part of the Mendip Hills, as well as the interesting tiny islands of Steep Holm and Flat Holm.
Brean Down is an outstanding example of calcareous grassland and supports endemic plant communities that provide for many important insect communities. Other important plant species growing at Brean Down and now growing at Bristol Botanic Gardens include the White Rockrose (Helianthemum appenninum). This is an attractive white flowered perennial sub shrub, which frequently grows on southern slopes. White Rockrose, Somerset Hair-grass and Dwarf Sedge (Carex humilis) are all particularly at risk due to scrub colonization. This highlights the importance of grazing to maintain grassland habitats. The National Trust introduced grazing by long horned White Park Cattle and British WhiteCattle (feral goats are already on Brean Down) to help keep the grass short and scrub species controlled. 
The rarity of the plants found on the Mendip Hills highlights how important collections, such as those held at the University Botanic Garden, are for ensuring the survival of plants teetering on the brink of extinction. Equivalent to a botanical savings account, these collections help ensure that if plant species are lost, they can be reintroduced back into the wild.

Branching out on your choice of Christmas tree

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By Helen Roberts

Nothing quite captures the Christmas mood more than seeing a beautifully decorated Christmas tree. Whether you choose to adorn one yourself or not, the Christmas tree is decorated and celebrated in many different countries and different nations have their own favourite species. 

The foliage of the Balsam Fir.
Photo by Robert H. Mohlenbrock @ USDA-NRCS 

I am particularly picky about the species of tree our family have and the overall shape of the tree. This fussiness stems from spending time living in Canada; high standards were set when our first Christmas tree was a wonderfully large and fragrant Balsam Fir (Abies balsamea), with its dark green, long lasting foliage. This tree is a very popular species used in North America for Christmas, and on our return to England I tried to find a nursery to buy a Balsam Fir for Christmas without luck. I did some research and eventually found a similar species, but also found out some interesting information about our celebrated Christmas tree.

Where does the tradition of the Christmas tree come from?

A Christmas tree. Photo by Malene Thyssen.
Licensed under CC BY-SA 3.0 via Wikimedia Commons – 

Most people know that in 1840 Queen Victoria’s husband, Prince Albert, brought a Christmas tree over from Germany and put it in Windsor Castle. The decorated tree, surrounded by the royal family, appeared in newspaper illustrations and from then on the tradition of the Christmas tree began in Great Britain. The Victorian tree was decorated with toys, gifts, candles, sweets and cakes hung by ribbons.

Queen Charlotte, the wife of King George III in 1800, however, introduced decorated trees to Great Britain even earlier. She decided to use a Christmas tree (a potted up yew tree) instead of a yew bough to be adorned with baubles, fruit, candles and presents. The tree was, therefore, not an unknown tradition in 1840, but became a common practice among the general public after the media publicity with Queen Victoria.  By 1860 the custom was firmly grounded in England.
The history of the Christmas tree goes back much further. The ancient Egyptians, Chinese and Hebrews used evergreen trees, wreaths and garlands in ceremony as they believed evergreens symbolised eternal life. European pagans celebrated the use of evergreens to ward off the devil, celebrate the winter solstice and provide a tree for birds during Christmas time. This tradition survived Christianity and in Germany the Yule tree was placed at the entrance to a building or in the house during the midwinter holidays.
A Christmas pyramid from approximately
1830. Picture by Klaaschwotzer,
via Wikimedia Commons.

The modern Christmas tree originated in Germany where the tree was decorated with apples to represent the Garden of Eden on December 24th (the religious feast day of Adam and Eve). It was also decorated with wafers (to symbolise the host) but later became cookies and candles, to represent Christ. The Christmas pyramid, a structure made from pieces of wood and decorated with figurines, evergreens and candles was also used in addition to the Christmas tree. It was the merging of these two structures in the 16th century that lead to the tradition of the modern Christmas tree.

It is rumoured that the religious reformer Martin Luther invented the Christmas tree. Apparently, one night in 1536 he was walking through a pine forest and was amazed by the beauty of the stars amongst the branches of the pine trees. It inspired him to set up lights on his Christmas tree to remind his children of the starry skies. The custom was widespread within German Lutheran communities by the 18th century and was a well-established tradition by the next century.

What are the most common species of Christmas tree in the UK?

The names fir and spruce are liberally applied to anything that looks vaguely like a Christmas tree. Those of us that are botanically minded are aware that the name “fir” is applied to members of the genus Abies (spruces are Picea).
I do not generally pick the common species of Christmas tree. For a while, my husband and I used to bring in a potted up Korean Fir (Abies koreana). It was small, but perfect in shape and form, and at a young age produces very pretty cones that are violet purple in colour and stand upright on the branches. However, we moved overseas and gave our tree a new home in my parent’s garden where it promptly withered and died after being contained in a pot for about 5 years!
Over the years we decided to go bigger as our decorations got more numerous after having children. We now settle on Abies fraseri (the Fraser Fir), a north American species very similar to Abies balsamea in its form and fragrance. These species are popular in North America (the firs are firm favourites) and in England the popular fir species is the Nordman Fir (Abies nordmanniana). This tree is originally from Russia and is known for its ability to retain its soft, dark green needles. Its conical shape and gaps between the branches allow optimal decoration hanging. The other popular fir in this country is the Noble Fir (Abies nobilis or Abies procera), which is glaucous green in colour with an upswept open conical shape.
Blue spruce foliage.
Photo by Nickolas Titkov from Moscow, Russian Federation

It is the Norway Spruce (Picea abies), however, that most people in England consider to be the traditional Christmas tree (it is the one I always relate with my childhood Christmases’). It has a lovely forest smell, though it loses its needles more readily than the firs. Other common spruce species include Blue Spruce (Picea pungens glauca), with its vibrant blue tinge and strong citrus scent (although it is very prickly), and the Serbian Spruce (Picea omorika), which is very popular in central Europe. It has a graceful conical shape with dark green colouring, soft needles and a pleasant fragrance.

For my family, the Fraser Fir reminds us of our time living in Canada and evokes fond memories of past Christmases’ with our children. In a few years, we will probably opt for a pot grown tree, which we can then plant out – hopefully with more success than the Korean Fir!

Botanic gardens: places of research, education and beauty

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By Nicola Temple

There are an estimated 3,400 botanic gardens around the world, many of which are associated with universities or other research institutions. This association with research institutions can give the impression that these gardens, Bristol’s own Botanic Garden included, are primarily research oriented and not particularly appealing to the public – nothing could be further from the truth.

In the last two years that I’ve been blogging for the Botanic Garden, I have taken myself to Kew Royal Botanic Gardens, Tresco Abbey Gardens in the Isles of Scilly, El Charco del Ingenio Botanical Garden in Mexico and the University of Alberta’s Devonian Botanic Garden. I’ve been keen to see how they differ from my local Botanic Garden that I’ve come to love. These gardens have been different in their sizes and plant collections and clearly differ in their annual budgets, but they have all been united in their commitment to educate and they have all been beautiful places to spend a day (or two).

The history of botanic gardens

One of the many spectacular species of orchid on display
at Kew Royal Botanic Gardens. Photo credit: Nicola Temple.

Botanic gardens seem to first make an appearance in the 16th century. They were set up largely as medicinal gardens where research and experimentation could be carried out on medicinal plants. They were often associated with medical schools and universities of the time.

In the 17th and 18th centuries, the focus of research changed as global exploration started to bring back new exotic species of plants. Some of these plants were medicinal in nature and were of interest for that reason. Some, such as spices, were of interest because of their economic value. Some were simply of interest due to their exotic beauty and many of the wealthiest families wanted specimens for their own collections. In the 18th century glasshouses and heated conservatories were built in some of the botanic gardens in order to keep some of the species alive that were being brought back from tropical habitats.

A corridor through the Agapanthus at
Tresco Abbey Gardens. The species was
introduced to the Isles of Scilly by the
proprietor of the gardens in 1856.
Photo credit: Nicola Temple.

The research focus of botanic gardens has continued to evolve to meet the needs of society. Today conservation, climate change and sustainability are the greatest challenges we face and as a result, many botanic gardens around the world have active research programs in these areas.  The decades, and in some cases centuries, of information collected by these gardens is proving incredibly valuable in terms of how the climate is changing and how some species are responding.

Botanic gardens play a critical role in conservation

In 2010, the Conference of the Parties to the Convention on Biological Diversity adopted an updated Global Strategy for Plant Conservation (GSPC). The University of Bristol Botanic Garden, along with botanic gardens around the world support this global strategy in every aspect of the work that they do.

The strategy recognises that without plants, life on this planet would cease to exist. The aim, therefore, is to halt the continuing loss of plant diversity. The five main objectives of the GSPC are:

  • Plant diversity is well understood, documented and recognised.
  • Plant diversity is urgently and effectively conserved.
  • Plant diversity is used in a sustainable and equitable manner.
  • Education and awareness about plant diversity, its role in sustainable livelihoods and importance to all life on Earth is promoted.
  • The capacities and public engagement necessary to implement the strategy have been developed.

The El Charco del Ingenio Botanical Garden in San Miguel
d’Allende, Mexico had many parts that were less formal than
other botanic gardens. Photo credit: Shelby Temple.

The University of Bristol’s Botanic Garden developed the Local Flora and Rare Native Plant Collection in response to the GSPC. In the eight habitat themed displays associated with this collection – Carboniferous Limestone grassland, woodland and cliff face (found locally in the Avon Gorge & Durdham Downs, Mendip Hills and North Somerset cliffs and coastal islands), Coastal Communities, Deciduous Woodland, Aquatic and marginal areas, hedgerows and seasonally flooded sedge peat meadow associated with the Somerset Levels  – are many of the rare and threatened native plants to these regions. The Garden is therefore a global repository for this plant material in both these living collections as well as its seed banks. Over the coming months, Helen and I will blog about each of the Garden’s collections in more detail, so stay tuned!

A place for learning

Cactus in flower at the El Charco del Ingenio Botanical Garden.
Photo credit: Shelby Temple.

The plant collections at the Garden are used extensively by the University of Bristol for undergraduate teaching as well as in graduate student projects. Beyond this, however, it is a place to learn horticulture, art, photography, garden design, and numerous skills from willow weaving to wreath making.

Formal courses and training through the Royal Horticultural Society are also held at the University Botanic Garden – it’s an ideal setting.

The Garden also offers tours – whether it’s a special interest group, school group or a group of friends wanting to join one of the summer evening tours. Having joined on a school group tour in the past, I know the volunteers are very good at tailoring the tours to draw together information the children have been learning in class with the collections on display.

A place to be inspired

A pollinator drinking nectar from milkweed (Asclepias syriaca)
flowers at the University of Alberta’s Devonian Botanic Garden
in Canada. Photo credit: Nicola Temple.

The collections, knowledge and expertise held at the Botanic Garden puts it in an ideal position to raise public awareness of the plants on display, our interdependency on plants more generally and critical issues facing many of these species, including changes as a result of global warming, habitat loss and invasive species. These are common threads in all of the communications put out by the garden.

More than this though, the Bristol Botanic Garden aims to foster an interest in plants and inspire people through its work. We can all feel somewhat paralysed by the plethora of environmental gloom and doom stories sometimes. Sometimes inspiration and awe about a species can spur people into action more easily than anger and frustration. The Garden’s annual Bee and Pollination Festival is an excellent example of this. Pollinators are having a tough go of it and a National Urban Pollinators Strategy is under development in the UK as I write this to try and improve the situation for this critical group of animals. All the important information is at the Festival, but overall this is a celebratory event – an opportunity to learn and get excited about how amazing pollinators are and how we are so deeply connected to them in so many aspects of our life.

A sunflower display at the Devonian Botanic Garden, Canada
was very popular with the butterflies. Photo credit: Shelby Temple.

The Garden can also be a quieter source of inspiration. I have now spent many hours sitting with camera in hand trying to get perfect flower shots or just simply watching bees move from flower to flower. Sometimes inspiration can be found in these quieter moments, surrounded by beauty, in a garden in a city.

African keyhole gardens open the door for school gardening

Posted on by andy.winfield

By Helen Roberts

A keyhole garden in Rwanda. 
Photo courtesy of Send a Cow.

Back in June, my son’s primary school, located in a small village on the edge of the Mendip Hills, built something called a keyhole garden in their grounds. Having no idea what a keyhole garden was, I thought I would offer up my services as a parent volunteer for the garden day.

The idea of keyhole gardens originated in Africa out of necessity. They enable families to produce food on dry, exposed and rocky soils – essentially land that is infertile. The gardens are shaped like a keyhole and act like an organic recycling tank using food and garden waste as fuel to grow vegetables.

The garden day at my son’s school was organised and facilitated by a charity organisation called Send a Cow. This charity helps families and communities in Africa by providing farmers with the skills and tools they need to farm using sustainable and organic methods. Farmers on the programme are given the gift of livestock, seeds and other assets and every farmer makes a pledge to pass on the gift of training, seeds and livestock to another family in need. 

The facilitators from Send a Cow held a morning workshop with the children to discuss building the keyhole garden and the materials needed. Two sixth form pupils from another local school were there to help with the session and contributed enormously to the discussion, engaging with their younger peers and getting them interested in the activities. These two students are hoping to run Send a Cow African Garden Day workshops themselves. 

A tip tap hand washer in Uganda.
Photo courtesy of Send a Cow.

Some of the children also learned about tip tap hand washers. These are a simple water conserving/hygiene device used in African countries aimed at improving hygiene and preventing the spread of diseases. Send a Cow shows families how to make them.

Laying the foundation

I joined the children in the afternoon to help build the garden. My pre-schooler was eager to muck in too as he is an avid gardener and had already donned gloves with trowel in hand in eager anticipation of the job ahead! 

The keyhole garden was to be located along a major walk way, on a patch of grass that would be visible to the children walking to their various classes. This would enable them to see what was happening with the garden on a day-to-day basis and judge whether the garden needed weeding or watering. A group of children were assigned the task of building the stone base around the patch of bare soil that had had the turf removed the previous week. This turf was recycled back into the garden via the school compost bins. 

The foundation of the garden can be made from
whatever resources are available. This garden is in Lesotho.
Photo courtesy of Send a Cow.

The prepared ground was a typical keyhole shape, with a 1.4 metre radius circle and an entrance triangle starting from the circle centre to the edge of the circle. The entrance is north facing to allow more room for sun-loving plants. The children worked hard moving and placing stones in a double layer for the outer wall- a little taster of the backbreaking work done by people who build dry stone walls. 

For all key hole gardens, the simplicity of the design means materials can be sourced locally. In Africa, this includes many creative construction materials, such as plastic bottles filled with sand, instead of stones or bricks for the main structure of the key-hole garden base. We used Mendip limestone. 

After the stonework, a steady flow of soil mixed with manure was wheel-barrowed across the school grounds and excitedly transferred by spade into the garden. The children had previously made the composting basket, which is central to the keyhole garden, out of runner bean canes (or sticks), string and chicken wire. This was placed in the centre whilst the soil was piled around it. Composting material was then placed in the compost basket, along with straw.

Planting it up

The finished garden at the primary school.

Planting up the garden was the most exciting part for the children. The volunteers had a line of seedlings lined up for the students to plant carefully. Typically, the vegetables commonly grown in African keyhole gardens include spinach, amaranth, gourds, Tithonia (eg tree marigold), chillies, sweetcorn and climbing beans. Plants with deep roots that require lots of feeding are planted near the centre of the garden. Herbs are added near the rock walls to help bind the soil and compost. 

In the Mendip school garden, tomatoes, lettuce, cabbages, peas, sunflowers, cornflowers, nasturtium and calendula were planted out. Flowers were added to the vegetables to add colour and other benefits. Nasturtiums are useful companion plants because black aphids, black fly and cabbage white butterflies cannot resist them and feed on them rather than the crops. 

“It was a fantastic day and the children really enjoyed it and still talk about it avidly,” said Mrs Savage, the school reception teacher. 

The African Garden Day informed the children about positive ways people in Africa are feeding themselves sustainably, but it’s also a long-term teaching tool and resource to get children interested in plants. 

“All the summer sunshine has done wonders for the African Garden created by the children last term,” said Mrs Williams, the school’s Head Teacher over the summer. “It is looking amazing and we are very proud of our achievement!”

There are plans afoot to develop a second garden, but more in keeping with Somerset traditions using weaved willow to form the base wall and compost bin.

African Garden Days is one of many programmes run by Send a Cow. It is the UK’s largest global learning project with approximately 30,000 children taking part. African Garden Days offers primary schools the chance to experience a fantastic hands-on day, combining classroom sessions with an outdoor challenge to create a global kitchen garden within the school grounds. It is aimed at Key stage 2 and 3 children, but also involves the whole school in an assembly and class session. The cost of running the garden day goes directly back to Send a Cow.

Green roofs part II: lofty havens for wildlife

Posted on by andy.winfield

By Helen Roberts

The green roof industry has been aided over the past few years by an unlikely character. The black redstart (Phoenicurus ochruros), a robin-sized bird of strange habits, has not only helped draw attention to the green roof industry, it has advanced development of green roof design.
The black redstart is unusual in its call, looks and ecological preferences. Its song starts with a hurried warble followed by a sound similar to that of scrunching of a bag of marbles. Males have a fiery red tail and the species has a propensity to hang out in industrial places.
Within the urban environment, brownfield sites can be rich in biodiversity and can be lost when they are developed. The story of the black redstart is inextricably linked to that of humans and urban centres. Black redstart population numbers have fluctuated in the urban environment due to human activity, and this is where the story of the black redstart has impacted the green roof industry in a positive way.
During and after the Second World War the black redstart population soared because bombsites provided a habitat that closely replicated their preferred habitat found on the scree slopes of the Alps. With redevelopment of areas of London, however, populations declined. Other cities also saw a drop in numbers as a result of development.

Laban Dance Centre in London.
Credit: rucativava,
CC-BY-SA-2.0, via Wikimedia Commons

Deptford Creek in London, an area that was earmarked for development, was important for its populations of black redstarts. The developers were pushed by wildlife groups to provide suitable habitat for the birds through the implementation of green roofs. This truly innovative solution to mitigate the decline in black restart populations led to the development of green roofs designed specifically for black redstarts. The rubbleroof of the Laban Dance Centre in London, installed in 2000, was the first of these in the UK. Rubble roofs, such as the Laban Dance Centre’s, replicate the features of a brownfield site and often incorporate materials from the original site. They have a mix of aggregate materials such as crushed brick and concrete, stones and boulders. The Laban Dance Centre roof also incorporates features such as logs and sand boxes in order to study nesting bees. It has been monitored since 2002 and a number of rare invertebrates have been recordedusing the habitat.
Numerous studies have shown that green roofs help support several Red Data book invertebrates and UK Biodiversity Action Plan species such as the brown-banded carder bee (Bombus humilis) and the nationally scarce Bombardier beetle (Brachinus crepitans) and that these green roof conditions can be replicated at other sites.

The right plants for the right roof

Incorporating the right plant species in to the design of a green roof is important for achieving biodiversity objectives. Simple sedum matting has been shown to have little ecological benefit for invertebrates, though they do provide sources of food for foraging bees in summer.
A truly exemplar green roof that is rich in plant species is the Moos Filtration Plant in Zurich, which cleans all the water for the inhabitants of Zurich. Yet, this green roof came about by chance as there was no original intention to create a green roof as part of the building design. When the filtration plant was built, the multiple roofs were covered in exposed waterproofing which subsequently caused the water below the roof deck to become polluted with bacteria due to high temperatures during the first summer. In order to moderate the temperature of the roofs, a 5cm sand and gravel layer was laid down followed by a layer 15-20cm deep of local meadow topsoil. This soil was teeming with flower and grass seed and it became a flourishing 30,000m2 meadow. Today these expansive roofs provide habitat for 175 species of plants, many of which are rare and endangered at a local and national level, including 14 species of orchid. The roofs now have special protection under Swiss nature conservation laws. 

Due to the pressures of habitat loss through urbanisation, it is becoming increasingly important for biodiversity to be retained. If land is lost at the ground level through building, then green roofs help provide stepping stones above for wildlife and can provide valuable habitat for flora and fauna that would not ever be found on a conventional roof. 

Botanists disperse some ‘big data’

Posted on by andy.winfield
Recently, Botanists at Trinity College Dublin launched a database with information that documents significant ‘life events’ for nearly 600 plant species across the globe. The database is the result of contributions from individuals working across five different continents, who compiled information on plant life histories for a near 50-year span, and is an example of big data.

What is ‘big data’?

Black pine (Pinus nigra), one of the species whose life
history data is part of the database, is seen against a
stunning backdrop of New Zealand. Credit: Yvonne Buckley.

In academic circles, the buzz-term across all disciplines seems to be ‘big data’, and it means exactly what it sounds like – a whole lot of information. More formally, of course, big data refers to data sets that are so large and complex that traditional methods of processing the information contained within them simply aren’t adequate. Big data draw upon many sources of information and represent a body of work that far exceeds what a single researcher, or indeed an entire research group, could gather in their careers.
While there are many challenges of working with big data – storing it, analysing, visualising it and ensuring its integrity to name a few – the benefits of working with such large data sets may make overcoming these challenges worthwhile. Repositories of such vast amounts of information can not only help foster collaborations, but they can be used to answer questions surrounding some of the most complex and pressing issues society currently faces, including climate change, food security, and mass species extinctions.
Of course, what is considered to be big data today will not be big data tomorrow as our management systems and computing capacity improve. This is the inevitable path of technological advancement; the Human Genome Project took over ten years (1990-2003) to sequence the human genome and now it can be done in a day for a fraction of the cost.

The importance of sharing knowledge

Plantago lanceolata at Howth Head, Dublin, Ireland – one of
the near 600 plant species that researchers have gathered
extensive life history data on. Credit: Anna Csergo.

The researchers at Trinity have made their database, called COMPADRE, freely available in the hope that other scientists access the information to advance their research. The size of the database means it can be used to help answer an infinite number of questions – such as how plant communities may respond to climate change or physiological processes that might provide insights into our own aging and health.
“Making the database freely available is our 21stCentury revamp of the similarly inspired investments in living plant collections that were made to botanic gardens through the centuries;” said Yvonne Buckley, Professor of Zoology at Trinity’s School of Natural Sciences, “these were also set up to bring economic, medicinal and agricultural advantages of plants to people all over the world. Our database is moving this gift into the digital age of ‘Big Data’.”
The approach of free knowledge sharing is becoming more common and is a critical step toward resolving some of our biggest challenges. The University of Bristol’s Cereal Genomics Group has made the wheat genome along with hundreds of thousands of molecular markers freely available through their searchable database CerealsDB. These data can be used in wheat breeding programmes to develop new varieties of wheat that are more resistant to disease or droughts or produce higher yields.

Our best chance of overcoming some of the global challenges of the 21st Century is to work together. Sharing knowledge through databases, such as COMPADRE and CerealsDB, will ensure every scientific contribution counts towards this united effort.