Many plants have a distinctive scent, think of sweet peas, jasmine or honeysuckle, or stand next to a pine tree on a warm, summer’s day.  The scent is due to the release of volatile organic compounds (VOC’s, often oils), produced by specific tissues or glands.  Often it is the nectaries within flowers that produce the scent, apart from their ‘job’ of producing the sugary nectar.  The nectaries may be found on almost any structure within a flower - petals, sepals, stamens, ovary*. The location of nectaries varies from species to species.  There are other structures that can produce scent, for example, trichomes, and osmophores. Osmophores are clusters of cells specialising in scent production.  Any part of a plant can release scent, for example, the leaves of eucalyptus, lavender or myrtle. The scent of a plant may include a variety of VOC’s, indeed there may be dozens of different organic compounds contributing to a particular scent.  Many of these compounds are terpenoids (isoprenoids).  They contribute to the scent of eucalyptus oil, lavender oil and the flavours of cinnamon and ginger. Scent may have a number of functions.  It may be released to attract specific pollinators - moths, butterflies, bees, hoverflies etc. (who have learned to recognise the scent).  The production of VOCs can be modulated, for example,  scent production may be turned off when a flower is pollinated.  A scent may also unfortunately be a signal to herbivorous insects to ‘come and feed’. So, scent have positive or negative effects. A scent may be produced to deter herbivory by certain insects.  Sometimes, plants have a different approach. For example,  when pollen beetles feed on oil seed rape, the rapeseed releases VOCs which attract the attention of other insects.  Specifically, those that will lay their eggs in the larvae of the pollen beetles. These insects are usually from the same family as bees, wasps and ants - the Hymenoptera (insects with membranous wings and a ‘narrow waist’).   The pollen beetle larvae are then ‘eaten’ from the inside by the developing parasitoid larva.  The release of VOC’s is affected by a number of factors temperature, light, circadian rhythms, physical damage and drought.  As the temperature increases so the amount of VOCs released increases (usually). This may be experienced in coniferous woodland.  Conifers give off a variety of volatile oils (i.e. biogenic VOC’s) that contribute to a unique aroma and the formation of aerosols found in the air in and around such woodlands and forests; it is most noticeable in warm weather.  [An aerosol is a ‘mixture’ of very small particles (solid or liquid) in air; other examples of aerosols include mist, cigarette smoke, or car exhaust fumes]. In snapdragons, the most scent is emitted at noon which tends to coincide with pollinator activity, in contrast tobacco plants scent release is in the evening / night when hawkmoth are active.  Drought reduces the ability of plants (like rosemary and thyme) to produce / release VOC’s, this in turn, has been observed to affect which pollinators visit their flowers.  Nectaries located within the flowers of a plant are sometimes referred to as nuptial nectaries, whereas those found in other parts are termed extra-nuptial.  

The (European) hedgehog population is in decline.  In Britain, the population has roughly halved in recent times and is considered to be vulnerable to extinction.  The Danish Hedgehog project, a citizen science project, headed up by Dr Sophie Lund Rasmussen* (also known as ‘Dr Hedgehog’ : link to YouTube videos) has been investigating the life span of hedgehogs.    This has been done by analysing the jaw bones of dead hedgehogs collected by volunteers all over Denmark.   The jawbone shows a line of reduced growth when the animal goes into hibernation, the number of lines equates to the age of the animal in years.  The oldest hedgehog found to date was 16 years old.  Sadly this hedgehog died after being attacked by a dog, which is not an uncommon cause of death for hedgehogs.   The study has revealed the average life span of a hedgehog to be roughly two years only, with males faring slightly better than females.  The study also found that the most common cause of ‘hedgehog death’ was crossing a road. Another finding was that the hedgehog population is quite inbred.  This may be due to the reduced population size and the difficulty hedgehogs face in finding a mate due to habitat fragmentation (garden fences, roads, railway lines which divide up the environment).  Inbreeding leads to loss of genetic diversity, which in turn reduces the overall fitness of the individual and the population. Hedgehog populations can be helped by Creating hedgehog friendly gardens by removing barriers to movement between gardens. Ensuring there is plenty of greenery /  plant life in the garden so there are earthworms, insects, snails etc. for hedgehogs to feed on. Avoiding the use of pesticides and slug pellets in the garden.  Also be careful with the use of netting, keep it above ground level.  Providing a shallow dish of fresh water and food (such as meaty cat or dog food), particularly during long dry spells. NB : ponds with steep sides can be a problem for a hedgehog if it falls in.  More information on hedgehogs can be found here : https://www.britishhedgehogs.org.uk/ Thanks to Nigel Palmer for his excellent hedgehog pictures, visit his hedgehog post here * https://www.biology.ox.ac.uk/people/dr-sophie-lund-rasmussen#tab-3324091  

The blog tends to write about trees in the context of woodlands and forests, but the trees to be found in hedgerows, parks, streets and gardens are important in many ways.  London is sometimes referred to as an urban forest, as it has some eight million trees within its boundaries.  Though their individual contributions of any given tree may be small, collectively the trees help with : Carbon storage  Carbon sequestration Air pollution removal Removal of pollutants (e.g nitrogen and sulphur oxides) Capture / removal  of particulates Reducing runoff, helping with flood mitigation  Noise réduction temperature regulation. The role of trees in temperature regulation has received some attention recently.   With climate change, many parts of the world have experienced periods of extreme hot weather / heatwaves.  Whilst it is true that extreme cold weather is associated with more deaths than hot, heat waves and the associated deaths are a significant problem.  Heatwaves, such as that experienced in 2015, have been associated with cardiorespiratory problems and premature deaths.   Cities, in particular, record higher temperatures than the surrounding countryside or the suburbs. the so-called urban heat island effect.  The lack of vegetation, the use of air conditioning systems, coupled with the dark asphalt of roads means that heat is retained / trapped; giving rise to the urban heat island effect.  On a summer’s day, some city centres may be some 10oC hotter than the surrounding countryside.  Europe saw its hottest summer last year, and its second warmest year.  Cities in southern and eastern Europe were particularly affected by recent heat waves. They tended to have significant urban heat island effects and low tree coverage.   In contrast, 27% of Gothenburg is covered by trees.  Studies / modelling by the Barcelona Institute for Global Health have indicated that increasing tree cover to 30% of the urban space could decrease the deaths associated with heatwaves / extremes of hot weather (perhaps by a third).  A number of cities, like Barcelona and Seattle have committed to increasing tree cover.  Indeed, Barcelona’s Trees for Life Master Plan is making progress towards its goal of covering 30% of the city with trees,  Barcelona is also encouraging green roofs.  Studies have also shown that ‘green spaces’ can have other benefits from reducing cardiovascular disease, poor mental health, and helping to improve cognitive functioning of children and the elderly.

Poplars belong to the same family as the willows. Like willows, they have a 'preference' for wet soil. There are a number of poplar species – white, grey and black poplar and the western balsam poplar,   A poplar that is common is the Lombardy Poplar, it is a variant of the Black Poplar and probably the most recognizable poplar,  as its branches grow almost parallel to the main stem.   It is a tall, thin tree. The leaves of black poplar (Populus nigra) are arranged along the stems in an alternate fashion. The leaf has a long, slender leaf stalk – which is slightly flattened. The leaf is sometimes described as ‘triangular’ or ‘diamond shaped’. When first formed, the leaves may have a bronze tinge and the young shoots, leaves and stalks have fine, tiny hairs.   The upper leaf surface is a dark green, whereas the lower surface is not such a deep green. In Autumn, the leaves may turn a vibrant 'banana' yellow. The bark of the Black Poplar is grey / brown and deeply fissured with age. The tree may grow to a height of 100 feet, but is usually smaller than this.  The species is dioecious, that is, there are separate male and female trees. In some parts of the country, like Cheshire, the number of Black Poplars is falling, due to changes in land management, a reduced need for particular timbers and an ageing population of trees.  The natural regeneration of black poplars is limited because : male and female trees need to be near each other the fertilised seeds are only viable for a short period  and the seeds need to fall on damp ground   Added to this, there is the risk of hybridisation with other forms of Poplar. So, The Canal and River Trust in conjunction with Chester Zoo have initiated a program to plant black poplar trees in Cheshire’s Weaver Valley.  They have taken cuttings from native Cheshire trees and raised over 1,000 new trees, which have been planted in sites across Cheshire since 1995. For example, male and female trees have been planted by the River Weaver (Hartford) to encourage future natural propagation. Such black poplars can help promote biodiversity, providing homes for moths, bees, birds and butterflies.   Should you have a portion of woodland that has damp soil, and are considering planting some black poplar, there is company that seems to specialise in Poplars : http://www.poplartree.co.uk/poplartree/.  It lists some of the uses / benefits of poplars.  

Various Wildlife Trusts are experiencing financial problems as a result of Ash Dieback.  Dead and dying trees are to be found in woodlands up and down the country, (some of which are managed by local Wildlife Trusts).    The fungus has its origins in Asia and has spread across Europe for the last thirty years. It was seen in Denmark in 2002, and has spread across the country by 2005.  It  is now to be found in  Austria, Belgium, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Italy, Latvia, Lithuania, The Netherlands, Norway, Poland, Slovenia, Sweden and Switzerland. It probably arrived here on imported (and infected) plants, though its spores are easily spread on the wind.  Once infected, the fungus affects the movement of water, minerals and sugars as the vascular system (xylem and associated tissues) is impacted.  Once a tree has been infected with the fungus, it may then be colonised by another pathogen such as the honey fungus (Armillaria spp).  Symptoms of ash dieback may include Shoot tips become black and shrivel, side shoots on young trees may die. Dead and ‘black’ leaves can be seen, their veins and stalks of turned brown.  Leaves shed early. Branches begin to dieback Diamond-shaped dark lesions form on the trunk near to dead side shoots.  In late summer, small white fruiting bodies can be found on blackened leaf stalks (see Jasper’s detailed blog). [caption id="attachment_39049" align="aligncenter" width="600"] the fungus emerging from blackened dead ash petiole.[/caption]   The dead and decaying trees pose a threat (as they become weakened and brittle), and need to be removed.  Removal is an expensive process and takes money from the Wildlife Trusts that would otherwise be used for habitat restoration, new planting etc. Apart from affecting the beauty of our woodlands and hedgerows, the loss of these trees has ‘knock on’ effects for other species.  Brown eared bats and barbastelle bats are known to nest in ash trees, the trees also provide perches and nest sites for birds and act as a substrate for epiphytes such as lichens and mosses.  The loss of ash tree will also affect the plants beneath, plants that like damp shady conditions such as lady fern (Athyrium filix-femina) and dog’s mercury; these may be replaced by light loving species / grasses. Featured image : Ash in winter Detailed information of Ash Dieback : https://cdn.forestresearch.gov.uk/2017/06/fcrn029.pdf [note this link downloads a PDF].  

In recent times, peatlands and areas of blanket bog have been recognised as important parts of our landscape.  Blanket bog is mostly found in wetter and more northern regions - in parts of Ireland and Scotland; in England a lot is to be found in Yorkshire.  Peatlands and bogs play an important part in controlling the run off of water from hillsides, plus they also represent an enormous store of ‘sequestered carbon’. The remains of plants (and animals) have been buried in wetlands but have not decomposed fully (usually due to the acidic conditions). Sometimes large chunks of trees are found in peat bogs, and occasionally even human remains (for example Tollund man) have been found.  Some of the peat deposits are incredibly thick and the material stored in them may be many thousands of years old.  Moorland ‘management’ techniques have been implicated in the severe erosion of certain areas, and the peat (that has accumulated over thousands of years) is being washed away. [caption id="attachment_32147" align="aligncenter" width="650"] Water logged conditions are ideal for peat formation[/caption] The UK has lost many areas of wetland habitat in recent times. A research team lead by Dr Swindles (Leeds University) examined many peatlands and looked at the changes that have occurred over the last two millennia.  They found that the majority of peatlands have become drier.  This drying out changes the role of a peatland from carbon sink to carbon source; i.e. releasing carbon into the atmosphere - contributing to global warming and climate change.  The streams and rivers that permeate these areas often turn a deep, rich brown as this organic material is washed out. [caption id="attachment_34388" align="aligncenter" width="650"] Stream flowing through peat moorland[/caption] Various efforts are being made to help stabilise these valuable ecosystems and a number of techniques to have been tried. At Fleet Moss, a North Yorkshire moor between Wharfedale and Wensleydale, the Yorkshire Peat Partnership project has been working to restore areas of degraded peatland by creating dams and reintroducing wildlife.  The conservationists have been using grass seed to try and stabilise the peat, hoping that as it grows and extends its roots, it will stop the peat from being washed away while allowing bog plants and sphagnum to flourish.  Sphagnum moss can hold 26 times its weight in water.   Their work is already bearing fruit,.  Originally, the land was largely acres of heather, with little variety in terms of the animals and plants that had made a home there. But over time, owls, frogs, foxes and weasels have appeared.  With time, the grass should stabilise the peat and allow bog plants to establish themselves. However, it has not been an easy process. Whilst the scattering of grass seed has worked in some areas, this does not always work everywhere, particularly on exposed sites; seeds can be battered by rain and wind.   Even at the height of summer, the weather on some of England’s highest terrain can be fierce, and scattering grass seeds on areas that are battered by wind and rain has proved to be problematic. So now in some areas a hydroseeder is being used where grass colonisation has failed. This is where green sludge and the bioengineering company TerrAffix come in. TerrAffix uses a hydroseeder to spray the mix of brash (chopped heather), grass seeds, fertiliser and a special adhesive (or tackifier), to areas facing particular challenges.  This equipment has been used to reseed prairies in the States, and can also be used on the steep slopes of motorways,   It will be some time before it is known whether this technique is successful in boggy and peatland areas.  If it does show signs of success then plugs of plants such as bog asphodel and sphagnum will be added, in the hope of recreating a more natural and diverse flora for the areas.   Further information on the restoration of peatlands can be found on Dr. Emma Shuttleworth's web pages and in articles such as this. Featured image is a 'book' made from bog oak.  

The soil and the litter layer in a woodland is teeming with many different forms of animal life, particularly invertebrates that include many types of insects (beetles, springtails), arachnids, spiders and mites (arachnids), centipedes and millipedes (Myriapods), roundworms (Annelids) such as earthworms.  One group of animals that is often forgotten is the woodlice, they are terrestrial crustaceans belonging to the same group as crabs and lobsters.  Their ancestors were probably amongst the first animals to make the transition from sea to land  (millions of years ago). Indeed, they are still confined to a moist / damp environment as they breathe through ‘gill-like’ structures on their back legs (pleopods) and their body surfaces are susceptible to water loss. Consequently, they are usually found in damp, dark places, under rocks and in decaying logs / wood; they tend to be more active at night (which again reduces the risk of dehydration).  To protect their offspring, their fertilised eggs are placed inside a fluid filled pouch (carried between the female’s legs, and they are provided with water and nutrients).  The young go through a series of moults before reaching maturity. Woodlice are detritivores, feeding mostly on dead plant and animal matter in the soil and leaf litter.  Once, they have ingested and digested this material, what remains passes out of their bodies and micro-organisms will continue its breakdown (forming part of what is termed the detrital food chain).  They excrete ammonia through their exoskeleton, so they have a ‘distinctive smell’.  The ‘blood’ or haemolymph of crustaceans contains an oxygen carrying pigment that is blue when oxygenated.  It is based around a copper atom, our red haemoglobin is based around an iron atom. There are five woodlice species that are common in the U.K.   The "famous five species”,  they are Oniscus asellus (the common shiny woodlouse), Porcellio scaber (the common rough woodlouse),  Philoscia muscorum (the common striped woodlouse),  Trichoniscus pusillus (the common pygmy woodlouse) and  Armadillidium vulgare (the common pill bug).  Common names for woodlice vary throughout the country.   Several of the names refer to the fact that some species can roll up into a ball (armadillo bug, roly-poly, roll bug).  Apparently, the collective noun for woodlice is a quabble.  

According to some interpretations of the bible, the Magi or ‘wise men’ travelled from afar bearing gifts of gold, frankincense and myrrh to present to the infant Jesus. The meaning and significance of these gifts has been debated over the years.  One things is clear - all were valuable materials as might have been presented to a king or deity.  Together with spices, frankincense and myrrh moved through ancient trade routes for thousands of years. Gold is a relatively rare element and as such is a precious metal that has been used for jewellery and coinage throughout recorded history.  It is a noble metal, that is it is relatively unreactive, resisting attack by most acids - with the exception of aqua regia, a mixture of nitric and hydrochloric acids. But what of frankincense and myrrh?   Their origins are not geological as both are plant products.  They come from a group of plants known as the Torchwood family or the Burseraceae.  These are trees or shrubs that have prominent resin ducts / canals.  The resin ducts are tubes, surrounded by cells which produce and secrete a resin into the canals / ducts.  The resin is viscous, ’antiseptic’ and aromatic (often smelling of almonds) and helps to prevents microbial attack (and may deter wood boring insects). Frankincense comes from trees of the genus Boswellia.  Nearly all species of this genus have a bark that produces an aromatic sap but it is B. sacra, (also known as the olibanum tree) that is the main source of frankincense (from its papery, peeling bark).  It is found in Somalia, Yemen and Oman, often growing in relatively inhospitable places.  To obtain the resin, the bark of the tree is cut and resin seeps out and is collected, rather like the tapping of a rubber tree.  The trees do not produce resin until they have reached a certain maturity and over-exploitation of the trees can lead to their death.  The seeds from heavily tapped trees are less likely to germinate than those from trees that have not been ‘drained’ of resin.  All Boswellia species are threatened by habitat loss, over-exploitation, and damage by long horn beetles. What is Frankincense used for?  The word derives from the Old French ‘franc encens’ meaning high quality incense.  Many tonnes of frankincense are traded each year and are used in religious ceremonies, and in the making of perfumes and natural medicines.  In ancient times, the Egyptians used it in the process of mummification, it was added to the body cavities together with natron (a mixture of sodium salts).  The resin has also been used in traditional Chinese medicine for its antibacterial properties and ‘blood moving’ properties. Like Frankincense, myrrh is a resin harvested by wounding the bark of a tree. The bark is a silvery grey, and the twigs are quite spiny (see image).  The resin that exudes is ‘waxy’ and quickly congeals becoming hard and glossy, darkening as it ages. The tree in question is Commiphora myrrha.  It is found in north east Africa - Somalia, Yemen, Eritrea and parts of Saudi Arabia.   The related Commiphora gileadensis, native to Israel, Palestine and Jordan, is also accepted as an alternate source of myrrh.  Myrrh has been used as an antiseptic in mouthwashes, and as a constituent in salve / ointment for skin abrasions, bruises and sprains.  It  has also been used in perfumes and  as a special flavouring for wine.  Like frankincense, it was used in making incense❋ and in the preparation of bodies for mummification / embalming.  In Exodus [30:22-24], God said to Moses to take the best spices and liquid myrrh to make a holy anointing oil.  Anointing oil is still used in certain ceremonies / rituals of both Eastern Orthodox and Western Churches.  In some cultures, it can be used to ‘fumigate’ or refresh a house, giving a warm, earthy and balsamic odour.  It is also said that myrrh is a powerful detoxifier, can lower cholesterol and stabilise blood sugar levels.  Both frankincense and myrrh were extensively traded in ancient and more recent historic times, along with various spices (such as cinnamon, ginger and nutmeg) across the Mediterranean and Arabian peninsula, through to India.  Interestingly, in Ancient Rome, myrrh was priced at five times the cost of frankincense. ❋ Incense can be made from various aromatic plant materials that produce a scent. The actual ingredients used vary by region / area. Apart from frankincense and myrrh, incense may contain cinnamon musk patchouli (from a plant of the mint family) sandalwood. Many thanks to Pixabay for images of frankincense and myrrh  (Leo_65, xbqs42  et al))   .