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.

Insect pollinators are currently in decline.  This is, in part, due to the loss of habitats and foraging resources for pollen and nectar.  Pesticides, like the neonicotinoids, don’t help. Lawns and pollinators. “No mow May” has been promoted by Plantlife to  provide a feast for pollinators,  tackle pollution,  reduce urban heat extremes, and  lock away atmospheric carbon Lawns in gardens, parks, recreation grounds etc. represent a significant proportion of green space in cities, towns and villages. If these spaces and suburban lawns are managed with pollinators in mind, then they could become an important source of foraging resources.  Now, there is evidence accumulating that this is the case.  A  recent study used the lawns at Ministry of Justice prison and court sites.   Each site contained four patches,  A patch mown as normal every two weeks - the control  A patch mown every 4 weeks A patch mown every 6 weeks A patch mown every 12 weeks Weekly surveys of pollinators and flowering plants were made throughout June to late August. Butterflies, bees, bumblebees, hoverflies and beetles were recorded as pollinators.   The patches that were mowed less frequently (6 and 12 weeks) had many more pollinators [in fact 170% higher than the 2 week patch], and more flowers.  The most common plants recorded included selfheal, daisy, dandelion, creeping buttercup, and white clover.  Apart from the increase in biodiversity, the patches were ‘visually pleasant’, contributing to the wellbeing of staff / prisoners and saved on lawnmower fuel (cost). Details of the study : https://conservationevidencejournal.com/reference/pdf/12801 Farms and Pollinators. Farms and their crops, such as clover and oil seed rape, can offer a rich supply of pollen and nectar to pollinators.    The ‘richness’ of this supply can draw pollinators away from more natural areas.  However, the pollinators can go from ‘feast to famine’, when the crop has finished flowering.   A Swedish study has followed the behaviour of farmland pollinators after clover flowering.  They found that if natural areas were available after the flowering of the clover, then pollinators [like different bumble bee species] became more selective in their foraging.  This reduces the intensity of competition between the various pollinator species.  Areas of natural vegetation on farmland are therefore important in helping pollinators adapt after crops (such as clover) have finished flowering. [caption id="attachment_33904" align="aligncenter" width="650"] Oilseed rape[/caption] https://www.sciencedirect.com/science/article/pii/S0167880924005735?via=ihub Gardens and pollinators. A study In the Boston area of the US has revealed that small gardens with a diverse range of plants are important to pollinators.  The researchers first used Google Street View to identify and categorise some 86,000 front gardens (or yards, in their terminology) across the area - ranging from lawns to diverse flower gardens. They then visited 500+ of these gardens when the plants were flowering [in 2021], identifying and documenting the plants in each.   The found that : Whilst the higher income areas tended to have more cultivated flower gardens, these gardens were home fewer wild flower (weed) species. Small gardens often had the richest diversity of plants in flower as compared to those with lawns. The authors of the study conclude “Dense urban areas are a promising target for pollinator conservation.” Detail of this study can be found here : https://www.sciencedirect.com/science/article/abs/pii/S0169204624002706?via=ihub