Trees and shrubs that grow in temperate regions, where the seasons alternate (warm / cold, dry /wet) create annual rings.  The rings formed in a deciduous tree (like beech, oak, lime) are generally quite noticeable when the tree is felled.  They may be counted to give an indication of the age of the tree.  Annual rings are formed because there is a difference in the creation of ‘wood’ / xylem tissue when growth is fast in the Spring and slow as Autumn progresses.  The thickness of the rings from year to year reflects the changing climate and environment that the tree experiences during its life. Xylem tissue is one component of a tree’s vascular tissue.  The xylem tissue conducts water and minerals around the plant, whereas phloem tissue transports sugars and other organic molecules.  Lying between these two tissues is the cambium.  This is a layer of dividing cells, which becomes active in the Spring forming new cells some of which will form new phloem tissue and others develop into xylem tissue. The cells that will form the xylem tissue undergo a series of dramatic changes.   The walls of the cells that will form the long tubes of the xylem are made of cellulose to begin with, but then they are strengthened with lignin.  Lignin is the ‘stuff of wood’.  It is a complex material - made from polyphenols and other substances such as pectins and hemicelluloses.  It is a waterproofing material that is highly resistance to decay.  It lines the tubes of the xylem so that water can be transported from the roots, up the trunk / stem to the leaves etc.  The xylem vessels that form in the Spring [early wood] have a greater diameter than those formed later in the year [late wood].  It is this size difference in the vessels that results in the visible ‘rings’ when a tree is felled. Careful study of tree rings can reveal information about climate, sometimes extending back through the centuries   using species such as the long lived Bristlecones. It has given rise to the discipline of dendrochronology [link opens / downloads a PDF].  This information can then be ‘combined’ with tree ring data from intact remains in cold, dry (and often high altitude) environments and material from archaeological sites.   Apart from measuring the ‘width’ of the annual rings by creating thin section of the wood that can be examined under microscope, it is also possible to use staining techniques to reveal which xylem tissue has a higher / lower, lignin / cellulose content.  By using a double staining technique with the dyes Safranin and Astra Blue, it is possible to identify which xylem vessels are rich in lignin, and which have more cellulose.  Tree rings which stain largely blue are formed from cells which have not lignified properly.  Lignin stains red.  A recent study of blue rings in Pine trees and Juniper shrubs suggests that blue rings are indicators of cold summers. These two species are typical of the upper tree line in Northern Norway. Furthermore, blue rings have the potential to weaken the pine trees, leaving them more susceptible to mechanical damage and / or disease.  This study has identified blue rings associated with the cold summers of 1877 and 1902, which might have been caused by the eruptions of volcanoes as far away as Ecuador and Martinique. Note : The xylem tissue in conifers is different to that of broad leaved deciduous trees.  It is made up of shorter structures called tracheids, which pass water from one to the next via pits - ‘pores’ in their lignified walls. For more information on Blue rings in Black Pine, click here  

Burrs or Burls? What’s in a name. What are they?  They are woody outgrowths found on stems, branches, and often on roots.  They are  typically rounded, somewhat bulbous in form.  Burrs develop as a result of rapid and uncontrolled growth,  leading to a dense and irregular wood grain beneath the external bark of the structure. The uncontrolled and abnormal growth may result from various stressors, such as :- Physical damage eg. wounds, where branches are lost in high winds, injuries as the result of boring insects, or damage from squirrels or deer. Infections caused by bacteria, viruses, or fungi may trigger burr formation  These infections can induce  hormonal changes that affect cell division. Environmental factors such as extreme weather events or pollution can influence tree physiology and growth, as can somatic mutations. In most cases, a burr does not harm a tree, indeed they may persist for decades.  If the burr formed due to injury to the tree, then it could even be considered protective.  However, If a burr develops on a branch then it may become so heavy that the branch breaks. Burrs may be seen on a variety of trees, but some species are more prone to developing them, notably oaks, maples, walnut, and birch.  Coastal redwoods are known to produce burrs of considerable size, sometimes reaching several metres in width and even encircling the trunk of the massive trees..  Although burrs may not be visually appealing from the outside, internally the complex grain pattern means makes them highly valued for woodworking.  They are used to create bowls, furniture, musical instruments and sculptures.  It is generally unwise to cut a burr from a living tree; instead they are typically harvested from fallen or dead trees. Thanks to Steve Sangster for Burr images.

In the southern parts of Britain, beech is a dominant woodland/forest tree, further north, oak is prominent.  Beech trees are often large with smooth, silvery grey bark.  They can grow to a height of 150 feet, with a stout trunk (perhaps 10 feet in diameter) and an impressive canopy. The leaves, certainly on younger trees, may persist throughout winter in a brown and withered state — a phenomenon known as marcescence.  The root system of the beech is shallow but extensive.  The large roots spread out in all directions, and establish mycorrhizal connections, often with fungi such as Russula and Laccaria.  The mycorrhizae help the trees by supplying mineral nutrients (like phosphate) and water.  In return, the trees provide various organic nutrients to the fungus. Despite these associations, beech trees are susceptible to drought.  After the drought of the summer of 1976, many beech trees died. It is not surprising that people are concerned about the ‘health’ of beech trees in light of climate change — higher temperatures, extreme weather,  specifically periods of drought.  It was thought that climate change would reduce growth of trees like beech through the increasing frequency and intensity of summer droughts. Recently, a study conducted by researchers at the University of Liverpool looked at tree growth data (annual growth ring and masting data) accumulated over more than forty  years and found that growth was indeed reduced (by some 28%).   However, the reason was that the trees were investing more energy into reproduction than into growth.  Beech trees are known for their mast years - see previous blog on masting. In a mast year, a tree will produce enormous quantities of seeds (beech nuts✝︎). However, it seems that the changing climate is causing a ‘breakdown’ in the masting process, and whilst the trees now reproduce more more frequently.  Total seed production and seed viability is reduced.   It may be that the diminished reproductive capacity of beech trees as a result of climate change will affect their ability to regenerate woodlands and forests in the UK and indeed across Europe in the coming years.   [caption id="attachment_41997" align="aligncenter" width="675"] Marcescence[/caption] ✝︎ Masting means that so many seeds that even the most voracious squirrels cannot consume all of them * After the summer of 1976, drought damaged trees were still dying some 15 years later.

At first, you might not notice them, but ants in a woodland are important. Their presence indicates healthy woodland, and the Forestry Commission recognises them as a ‘keystone species’ in the woodland / forest ecosystem and encourages woodland owners to treat them sympathetically.  Ants, like bees and wasps, belong to a group of insects known as the Hymenoptera .  These are insects with membranous wings and narrow ‘waists’. Like bees, ants are ‘social insects’  and within their nests, there is a division of labour (workers, soldiers, queens).    There are four main species of true wood ant - Formica rufa, F. aquilonia, F. lugubris and F. pratensis. Ants are important for a number of reasons, for example :- They help disperse seeds.  They manage pests by preying on herbivorous insects that damage leaves They contribute to nutrient recycling, t Their nests provide a habitat for a whole range of invertebrates that live specifically in wood ant nests. For example, the woodlouse  (Platyarthrus hoffmannseggii), which has ‘lost’ its eyes and colour and is completely adapted to living in the dark recesses of the ants’ nests. They are a source of food for various predators including woodpeckers. Through the building of nests, they affect the soil profile, the drainage and permeability of the top soil, and help with the distribution of various nutrients.  A wood ant colony nest can persist for many years and survives so long as there is a queen / s present.   During the winter months, only queens and a limited number of the workers live on deep inside the nest. Once the temperature begins to rise in the Spring, then workers will begin to emerge and start to forage – and the queen(s) will begin to start laying eggs again.   Fertilised eggs will give rise to female ants, and unfertilized eggs give rise to males.   The males and queens have wings, and are bigger than the workers. The life expectancy of a worker is about 60 days.   Ants such as the southern wood ant [Formica rufa]. build large, ‘thatched’ nests, (see the film link below) which may contain many thousands of workers and queens (up to a quarter of a million). An ant nest is instantly recognisable, it looks like a roughly shaped dome, made from an untidy heap of leaves and twigs – with ant trails leading to and from. The heart of the nest is deep underground, whilst on the surface is the dome shaped ‘thatch’. The thatch consists of a variety materials in the thatch – small twigs, moss, heather, pine needles.   These materials are positioned so that they  not only intercept the sun’s rays to help warm the nest  but also are laid in such a way that water / rain runs away from the nest, reducing the risk of flooding.  Some ant species build their nests in /on gravel or sandy / stony soils - which reduces the risk of water logging. Like many insects, ants make use of pheromones (volatile chemicals). For example, to lay paths to the nest. The study of ant trails and ant behaviour has inspired computer programs / simulations to the “travelling salesman problem”, that is finding the shortest route round a large number of fixed locations (think of the Amazon’s driver’s day!  Woodlands TV has produced another film that focuses on woodland ants.  The film, presented by Giles Pitman, can be seen either on this website or on YouTube https://youtu.be/9wtvwlL2Wzg. Interesting fact : Ants can spray formic acid from their abdomen – when threatened. This smells like vinegar and is thought to be a deterrent to birds or other predators.  

Walking through a woodland you may see an ash tree or beech tree with black blobs on it.  The black blobs are often on dead branches or on branches that have fallen from the tree. These blobs have various names from coal fungus to cramp balls* or King Alfred's cakes. Like so many things in woodlands, once you know to look for these, you might see them quite often. These black lumps are usually hard, semi-spherical and about 3-4 cm in diameter.  They are the fruiting / reproductive bodies of a fungus, which finds a home in the dead wood of the tree.   The scientific name is Daldinia concentrica.  The blobs are pinkish brown colour when first formed but darken with age and may become somewhat shiny. It is said that King Alfred, when in hiding from the Danes, once allow some cakes to burn by failing to take them out of the oven. These fungal bodies, which look as if they have been burned, are a reminder of his inattention and hence are nicknamed “King Alfred’s Cakes”.  The fruiting bodies can be very useful for lighting fires because the inner ‘flesh’, once dried out, can be easily lit from a “firesteel”.  This is an artificial flint which creates a spark for starting fires, much used by ‘bushcraft people’.  A spark or two will ignite the dried flesh of the fungus.  Though this material burns slowly [like a barbecue briquette], once it has been lit one can transfer the glowing part to a ‘ball’ of tinder (for example, dried goosegrass) and get a fire started. [caption id="attachment_15473" align="alignleft" width="300"] Internal concentric rings of the fungus[/caption] Now WoodlandsTV has produced a film about these interesting ‘cakes’ and how to use them to make a fire.  Matt Clarke demonstrates how to start a fire using a small piece of this dry fungus and some dried vegetation. .  This can viewed either here on the woodlands web site or on YouTube :  https://www.youtube.com/watch?v=5ulGcEHN-k0.          it was believed that carrying the fungus would protect people from attacks of cramp.

City temperatures are rising across the Earth.  Heat stress causes illness and even death. Between March and June last year, India experienced record-breaking temperatures, with 37 cities surpassing 45oC. Hundreds of people died from heat death and over 40,000 heatstroke cases in 17 states were recorded.  Increasing urban temperatures also mean greater use of air conditioning (and associated energy use).  In an attempt to mitigate these rising temperatures, many cities have implemented tree planting programmes, e.g. One Million Tree campaigns. During the day, trees cool cities by: Blocking the sunlight from reaching certain areas The loss of water vapour (transpiration) via their stomates - tiny pores on the underside of leaves Changing the flow of air in and around trees and buildings. These are the positive aspects of trees in cities, but there can be a downside to their presence. The heat build-up  stored in roads and buildings during the day can irradiate back into the atmosphere at night, but it can be ‘trapped’ by a dense leaf tree canopy. Cambridge researchers have now analysed the results of some 182 recent studies of trees in different cities and countries / climates, and have reported that : Urban trees can result in an air temperature reduction of some 12oC as experienced at the pedestrian level Trees reduced the peak monthly temperatures in most of the cities studied The cooling effect varied significantly, according to the tree species present, the urban layout and the climate the trees experience. Seemingly city trees exert a greater cooling effect in hot and dry climates, and less in hot and humid climates.  For example, in tropical rainforest climates [which experience very high humidity] then the day time cooling effect may be as low as 2oC, and the warming effect at night +0.8oC.  The study also noted that cities with an ‘open’ urban layout with a mix of evergreen and deciduous trees (of different sizes) were more likely to experience a good cooling effect.  However, in cities with a dense or compact layout, such as Cairo or Dubai, planting mainly evergreen species was found to be more effective. The study concludes that whilst urban planners need to provide more green space in cities,  they must also carefully consider the ‘mix’ of trees that are planted.  The study also emphasises that trees alone will not provide a solution to rising temperatures, but the use of solar shading and reflective materials will play a part, as will the nature and structure of the urban layout. Full details of this study can be found here :  https://www.nature.com/articles/s43247-024-01908-4  

Woodlands TV has just released another film, which discusses the pros and cons of tree planting in an area, as opposed to allowing natural regeneration.  Many years ago, Kenneth Mellanby [Director of a Research Station near Huntingdon] thought that it would be interesting to watch what happened to a barley field if it was left to its own devices.  The 4 acre field was ploughed for a final time in 1961 and then ‘abandoned’. The field sat next to an area of ancient woodland - Monks Wood. The changes in the field were monitored in succeeding years and eventually becoming known as the Monks Wood Wilderness Project.   In the first 10 to 15 years, a thorny scrubland developed with hawthorn and bramble.  Birds were attracted by their fruits and berries.  The birds dispersed the seeds of the fruits across the plot, and also brought in seeds from other areas (such as the adjacent woodland).  The bramble and hawthorn scrub afforded protection from the wind and herbivores [rabbits, deer etc] for young, delicate tree seedlings.  Wind blown seeds arrived in the area, such as ash and field maple.  Other tree seeds were deposited by birds, Oak began to grow.  Acorns were probably carried in by Jays, who bury them as a winter food store.  An acorn is a rich food source - containing fat, carbohydrates, proteins and micronutrients.  A single jay can scatter many hundreds of acorns each year.  They store more than they need, so some will germinate and grow on to saplings.  Whilst many different birds spread tree and shrub seeds, jays have been known to carry acorns significant distances and probably contributed to the northward spread of the Oak as the glaciers of the last Ice Age retreated. A mature oak tree can provide food and / or a home for many species of animals, plants and fungi. The former barley field has been monitored over the decades, and by 2014 it had become an oak woodland.  This despite the usual depredations of Rabbits, Hares, Muntjac Deer and Roe Deer which have been present at various times over the years.  So given time, former agricultural land can revert (rewind) to mixed deciduous woodland with a diverse collection of plants and animals.  For further details of Monks Wood - visit https://www.naturewalkswithcarol.com/monks-wood-nature-reserve.html The woodlands TV film features ecologist Connor McKinnie who highlights key factors to consider when planning woodland creation, such as tree protection methods, planting pattern, and species. This is the second film with Connor, exploring aspects of rewilding.  The first film is presented below : [embed]https://youtu.be/HZNX9hTzQaU?si=-Ivv4aziPzi4a3cA[/embed] The latest film may be viewed on YouTube by following this link : https://youtu.be/Qx7uiOlGjFY

The Lambir Hills is a national park on the island of Borneo.  It is a small park composed largely of mixed dipterocarp forest, with some small areas of 'kerangas' (heath forest). The forest is monitored and biologists previously recorded  237 species of birds,  64 species of mammals,  46 species of reptiles and  20 species of frogs 1175 different species of tree in the national park.  But now, large mammals (e.g. gibbons and sun bear) are absent or very rare due in part to the small size of the forest but also the impact of illegal hunting.  The most recent surveys failed to find many of the park's resident birds and mammals. As a result of the loss of these species, the make up of the forest has changed markedly in the matter of a few decades. Whilst there are now more trees, with lots of saplings, the variety of trees has declined, particularly of those tree species that rely on animals to disperse their fruits / seeds. The seeds are ingested and pass through the gut of birds and mammals, and finally expelled with a small amount of ‘fertiliser’.  The loss of seed dispersers is having a significant effect on the composition / make up of the forest. There is concern that this sad tale is being played out across the forests and woodlands of Europe.  Seed dispersal is essential in maintaining the biodiversity of woodlands and forests.  Many European species of plants and trees are dependent on animals / birds for the dispersal of their seeds, and it is known that the numbers of certain animals and bird are in decline.  The dispersal of seeds is increasingly important as the landscape becomes increasingly fragmented (due to agriculture / roads, urban expansion species may need to extend their range as a result of climate change (fires, drought etc). But which animal / bird disperses which plant seed / fruit?  There are thousands of plant species and hundred of different animals that might act as dispersers (even ants).  Sara Mendes at the University of Coimbra has started on this mammoth task.   She has identified nearly 600 species that have adaptations for animal dispersal (such as flesh fruit), and nearly 400 animals that ‘transport’ such seeds.  Some of the dispersers eat more than one type of fruit, so the number of interactions is legion.  However, sadly many of the seed dispersing animals / birds are dwindling in numbers or rated as threatened by the IUCN.  For example, the garden warbler (a migratory species) is known to spread the seeds of some sixty different plants but its numbers are in decline.  The redwing is another migratory bird, but which is amber listed. Another worrying feature is that many plant have five or fewer animals / birds to disperse their seeds.  Unfortunately, in many cases, we do not know which disperser species are important to which plant species, or whether another bird or animal could take on the role. Dipterocarps :  a family (Dipterocarpaceae) of tall, hardwood, tropical trees mainly found in southeastern Asia . They have a 2-winged fruit and are a valuable source of  timber, aromatic oils, and resins.