A sense of touch in plants.
Climbing plants like sweet peas can ‘feel’ their way around a support, a twig or fencing. Charles Darwin, who had an interest in climbing plants, described Clematis as a leaf climber. Clematis has compound leaves with three to five leaflets, It uses the stalks of the leaves or the leaflets to climb. Darwin noted that contact with another structure was enough for the leaf stalk / petiole to start bending around it. This ability to respond to touch is termed thigmotropism. It is a growth response. The growth rate on the side of the stem that touches the 'support' is slower than on the side opposite the point of touch. As a result the stem begins to curl around the support. The same response is seen in plants that climb using tendrils, such as White Bryony. Its tendrils are thin, wiry structures along the stem that ‘reach out’ into the space around a plant until they come into contact with something they can ‘grab’. Once contact is made, the tendril curls, forming a coil. This sense of ‘touch’ has recently been investigated using Thale or Mouse Ear Cress. It has been shown that the veins of the leaves respond to touch. The investigators used small glass beads to apply a small but distinct pressure, and recorded a series of rapid electrical signals (not dissimilar to those seen in nerves). Even when the veins were removed from the surrounding leaf tissue, they still showed electrical activity so the response was not reliant on surrounding cells. The electrical activity was also associated with proton pumps (moving hydrogen ions). The sensitivity of the veins to touch may be associated with the plant’s defence mechanism. Animals like aphids use their mouthparts (stylets) to penetrate the vascular tissue in the veins. The jasmonate system is involved in wound response. Another plant, the Venus fly trap (Dionaea muscipula), also responds to touch. It catches prey (insects and spiders) by means of touch. Dionaea catches its prey with a trap, formed from the terminal portion of each of the plant's leaves. The trap is activated by tiny hairs on the inner surfaces of the trap. When a hair is touched by an insect or spider crawling along the leaves, the trap prepares to close but it only snaps shut if the hairs are touched again, within approximately twenty seconds of the first stimulus.
Many hedgerows were planted originally to keep livestock, such as sheep, cattle, pigs, chickens in specific areas. Some hedgerows were planted to define boundaries – ‘who owned which bit of land’. Hedgerows often surround fields. The word ‘field’ comes from Old English ‘feld’, meaning 'an area of felled trees / open country'. The establishment of many hedgerows was associated with the process of enclosure; a change in land use from arable to pasture (for sheep). Open fields and common land were enclosed by hedgerows, over many years the landscape of England changed. The C20th witnessed the opposite process, the removal of hedgerows for the creation of larger fields to accommodate larger machinery. In the decades following the end of the second Word War, it has been estimated that a quarter of a million miles of hedgerow have been ripped out / lost. Fortunately, there are now policies in place to halt or even reverse the loss of hedgerow. Hedgerows are recognised as an integral part of our landscape and play an important role in the maintenance of biodiversity. They provide habitats for a variety of animals and plants. Many species of birds nest in hedgerows, such as song thrush, yellowhammer and tree sparrow. Different species favour different heights within the hedgerow. Some species nest near the ground such as wrens and dunnocks, whereas others nest higher up (eg. Bullfinches). The greater the variety of plant species in a hedgerow, the better the supply of pollen, nectar, fruits and seeds. Ivy for example will produce flowers late in the year and offers a source of nectar and pollen. Hawthorn, blackthorn and holly offer fruits in the winter months for birds and small mammals. Hedgerows and hedges have to be be maintained. Such management may involve planting of trees or shrubs to fill gaps, coppicing, laying or cutting back. [youtube=http://uk.youtube.com/watch?v=Andv7a0NPEc 425 350] However, the effects of pruning and cutting back during the bird-nesting season can be disastrous. Mechanical flailing of a hedgerow is fast, effective and the regrowth is generally slower, but its effects can be particularly bad on birds. They may abandon their nests and / or their eggs or chicks may be destroyed. The pruning / flailing may also reduce the insect populations of the hedgerow (or other other food sources) on which the birds depend. Hedge pruning maintenance is :- ideally undertaken outside of the nesting season. and only done every second or third year. [caption id="attachment_25527" align="aligncenter" width="600"] A flailed hedge[/caption] Hedgerows also support vital insect pollinators : butterflies, hover flies, moths and bees. These insects help with the pollination of crops such as oilseed rape, legumes and fruit trees. Other insects can help with crop yields by predating upon crop pests, such as green fly and blackfly (these may spread viral diseases on crops such as sugar beet). Insects may overwinter in the hedgerow and move into the fields come the Spring, as the aphids start to increase in number. If trees are left in situ, they may achieve veteran status. Then their rough bark, cracks, holes and dead wood will support a diverse range of species. Owls, kestrels and bats may come to nest. There are also niches that offer opportunities for epiphytes, mosses and lichens. The dead wood may be home for saproxylic beetles. Hedgerows also act as corridors linking to other hedgerows, woodlands etc along which animals can pass (for example, hedgehogs and other small mammals). Hedgerows provide important wildlife corridors across agricultural landscapes. They provide food for insects, small mammals and birds (due to the range of plants and their different flowering and fruiting times). They provide nesting and roosting sites for birds and bats, and ‘homes’ for a variety of small mammals. Many insect species over winter in hedgerows. The trees and woody shrubs help with carbon sequestration. Hedgerows offer a windbreak, reducing wind speed and hence lowering soil erosion, they may also offer shelter to animal stock. The roots also help stabilise the soil. [caption id="attachment_40483" align="aligncenter" width="675"] Hedge with beech, nettle, dog rose, brambles, hazel and ash - amongst others[/caption]
Losing woodlands and forests.
Across the world forests and woodlands are under threat, suffering fragmentation and shrinkage. This is not good news for the plants and animals that rely on these habitats for their survival. In a large forest or woodland, animals can move around over considerable distances in search of food / partners - without having to leave the area that supports them. Similarly, plant seeds when dispersed are more likely to find the micro-climate that they need for germination and subsequent growth (humidity, shade, soil type etc). Some species have very ‘exacting’ requirements that can only be met in the heart of a forest or woodland. For example, there is a frog that is restricted to undisturbed mountainous forests in Borneo. Sadly, recent surveys suggest that many forests continue to suffer from fragmentation / loss of area. The two main reasons for this loss are : clearance for agriculture (palm oil plantations etc) - this has mainly affected tropical and sub tropical area. Sometimes fires are used as a deliberate ‘tool’ to clear an area of forest so that the area can then be used for agriculture. wild fires - these have affected the Boreal Forests but also regions of the Amazon Basin. In areas like Siberia and Canada, drought and high temperatures have lead to extensive fires. (Zombie fires are underground peat fires that smoulder in the winter months but reignite when the ground dries in the Spring or Summer.) Recent times have seen extensive fires across Siberia, Canada, parts of the West Coast of America and Australia. Woodlands have experienced fragmentation due to the expansion of agriculture, the building of motorways & roads, and the expansion of housing. Wild flower meadows have suffered even more dramatically - with some 90+% lost in relatively recent times. Obviously fires are devastating locally, killing vast numbers of animals and plants. Fire also destroys the organic content of the soil and its complex microbial population. The plumes of smoke released by fires (such as those seen in Canada and Australia) spread extensively. The Canadian fires (883 fires raging at one point) left mile after mile of blackened forest, and forced hundreds of people from their homes. The smoke spread far beyond Canada’s borders, as far away as parts of Europe. New York City was ‘bathed’ in an ‘orange haze’ and experienced a hazardous level of air pollution. The plumes from such fires are rich in black carbon soot. The soot particles absorbs solar radiation, keeping heat in the atmosphere. Recent analysis of smoke plumes indicates that there is also ‘dark brown carbon’. This consists of a previously unknown type of particle and whilst these particles absorb less light per particle than black carbon, they are approximately four times as many brown carbon particles in wildfire smoke (compared to black soot particles). There is also the suggestion that these brown particles retain capacity to absorb solar radiation for longer.
Sweet chestnut finger-jointing at InWood in Whitesmith,East Sussex.
Chestnut coppice grows in abundance in the South East of England, especially in Kent and East Sussex. However it is quite small diameter, being harvested about every 15-25 years. The timber is very strong and resistant to rot. For some uses it is better than oak and unlike softwoods it does not need treating with chemicals. The problem is how to turn these relatively thin stems into useable pieces of timber and a small company, InWood, has found an answer. I was visiting The Woodland Centre to collect a batch of six-inch decking that the factory team had made for me, and they offered me a tour round the factory. Their answer is to glue it together using finger-joints which are actually stronger than the wood itself and you can use it for decking, cladding and even structural beams. My decking boards had machined-in grooves to stop it being slippery and there were other options for width such as their three-inch or four-inch boards. Peter Black, the factory manager, explained how they buy sweet chestnut planks and process them by sawing them to width, taking out the knots and any wood that is rotten or infested with woodworm. He says that there are also occasional shotgun pellets which need removing - many of the chestnut coppice woodlands in East Sussex are used for pheasant shoots. The sawing produces short pieces of the same width and thickness but the highlight for the visitor is seeing their German machine which automatically cuts a tooth-like pattern in each end and puts polyurethane glue on it. These sections are then pushed together to make long, virtually defect-free planks. The factory generates plenty of waste wood which burns well and burns hot - it is either used for heating the workshop or sold for firewood. Enviously I looked at the part of the workshop where they use a huge hydraulic press to make “Gluelam”, being laminated beams from planks. These bigger timber beams have lots of advantages over the alternative of using large sections of tree trunk: the wood is much more stable, is less likely to twist & warp, longer sections can be made and there is often less wastage. InWood’s front man is Alan Ellis whose phone number is 01825 872550, and he is happy to supply trade or retail. On their website (www.in-wood.co.uk) you can find some spectacular garden rooms which they make from laminated chestnut. We got our Sweet Chestnut decking from InWood because of the quality, and their sensible prices. This method of producing timber supports sustainable British Forestry as well as the coppicers. Successive generations of coppice workers have used their skills since at least Roman times, when sweet chestnut was first introduced to southern England.
Birch trees and their products.
Hazels, alders, and hornbeams belong to the Birch family - the Betulaceae. The white birch, silver birch has the scientific name Betula pendula. The birch is the national tree of Finland. As trees go, it has a rather slender, delicate form, and may be seen swaying in the wind. Its silvery / white bark develops blackened fissures with age. Early in the year it forms flowers, the male flowers in the form of catkins. The female flowers become a dark red colour after pollination, eventually forming small, wind dispersed, winged seeds. The male catkins release large quantities of pollen (before the leaves emerge). This pollen is the dominant tree pollen in Northern Europe (in Spring). It is often implicated in allergic responses such as rhinitis (runny nose / sneezing) and asthma. Birch is a pioneer species, it can colonise open spaces, and disturbed ground quickly. It grows fast and once established, it helps ‘protect’ or shelter slower growing species, like Oak. It has a limited life span, perhaps a maximum circa 70 years and then gives way to longer lived species such as Oak and Beech. The tree can provide a home or food for many species of insect, woodpeckers may nest in the trunks and other birds may feed on its seeds. The tree is quite susceptible to the honey fungus, which is the name given to several species of the fungus Armillaria. The fungus attacks and kills the roots of a number of trees and shrubs. One symptom of honey fungus is a white fungal ‘layer’ between the bark and wood, often at ground level. Clumps of honey-coloured mushrooms sometimes appear briefly on infected stumps in Autumn. The birch tree has had many uses over the years, some dating back to the neolithic period. It has been used to make perfumes, adhesives, and besom brooms. Bundles of birch twigs were used for corporal punishment, and the twigs may be available in saunas to stimulate blood flow in the skin! The wood of the tree is used in furniture making, creating veneers and in wood turning. However, it is the bark and sap that have attracted most interest and have many uses. Slabs of the bark are used as roofing shingles, and strips of it were / are used to make bast shoes and in handicrafts. The bark has been used in tanning, and when heated a resin forms which can act as a waterproof glue. In Spring, large quantities of sap rise up the stem(s) of the tree and this can be tapped. The sap is best collected in early Spring as, if collected later, it tends to have a somewhat bitter flavour. Birch sap contains sugars, amino acids and minerals (e.g. manganese), it may be drunk fresh or fermented. Bottled birch water is available online. In recent times, attention has focused on wood pulp from birch. It is a rich source of plant sterols and stanols. Sterols and stanols are naturally occurring substances that have a chemical make up that is similar to cholesterol. They are found naturally in small quantities in vegetable oils, legumes, seeds, nuts, legumes, grains, and vegetables. Back in the 1950’s, they were found to lower cholesterol levels in the body, if eaten in large enough quantities. One called beta β-sitosterol was particularly effective in reducing the absorption of cholesterol from the intestines. However, there was the problem of finding a rich enough source of these compounds. This was ‘solved’ when it was found that wood pulp could yield the compounds in quantity. Now margarine-like spreads, milks and yoghurts are available that contain β-sitosterol or similar stanols in sufficient quantity to effect a lowering of blood cholesterol levels. β-sitosterol has also been to improve urinary flow in men with prostate enlargement.
Deer control – shoot to kill and cull, or are there other solutions?
Deer are eating out the bottom of our woodlands and wildlife is suffering. Although the size of the national deer population is not known for sure it is probably at its highest for a thousand years. There may be as many as two million deer in the UK’s countryside. There are several types, such as the two native species, being the Red deer (Cervus elaphus) and the Roe deer (Capreolus capreolus) - which is the most populous of the larger deer being, perhaps, 500,000 animals. Then there are the ones the Normans introduced, the Fallow deer (Dama dama) with a population of at least 150,000. On top of that there are three species of deer which have been introduced from the Far East including the Sika deer (Cervus nippon). The other two from China are very different - there are relatively small numbers of the Chinese Water deer (Hydropotes inermis), whereas there are probably hundreds of thousands of the small and mostly nocturnal Muntjac (Muntiacus reevesi). They are all hungry and they all love woodlands. Most people believe the deer population needs to be controlled, or even reduced in number, but the range of species makes that harder to do. If you reduce the population of one type of deer the others will expand their numbers. Culling, or shooting, is certainly helping but stalkers are usually only interested in the larger species with enough meat to make it worthwhile and this leaves the muntjac space to thrive. Here is a film we made of a Scottish deer stalker explaining her job and how her stalking helps with environmental management: [embed]https://www.youtube.com/watch?v=ISh2sN-Ljy8&ab_channel=WoodlandsTV[/embed] Megan: “99% of stalking is looking through the binoculars.” Other ways of controlling the deer population are fencing them out but that is expensive and unlikely to work in the large open areas of the British countryside such as the moors and the uplands. Another potential method of control is introducing predators such as lynx or other larger hunting species. This meets some resistance from the public and the unintended consequences are that the predators might well go after different species altogether and occasionally humans. Most work is going on with contraceptive solutions so that the birth rate is reduced and less killing or culling is needed. This is also being researched for controlling populations of wild boars and grey squirrels to keep their numbers in check. It means getting the drugs to the target species and usually to the females which is often done through their foodstuffs, using food hoppers which are designed to be only accessible to that species. Other approaches include sterilization through injections and the Deer Initiative partnership has done a lot of work on examining different methods of biological control of deer numbers: https://www.thedeerinitiative.co.uk/pdf/contraception-and-wild-deer-control.pdf It’s not easy. Even if one of these methods works, it will require an enormous effort to cut deer populations particularly of the smaller and more evasive species such as the muntjac. What do you think should be done? Meanwhile , deer are dangerous to motor cars. The British Deer society estimates that annually there are between 40,000 and 70,000 accidents involving deer and this leads to about 700 human injuries, and far more deer fatalities!. So, in short, an overpopulation of deer is a large and growing problem: they damage the flora in woodlands, they eat young saplings, they compete with other mammals for space, they eat farmers’ crops, they carry ticks and they cause road accidents. The challenge of controlling the deer population is very real.
The DiversiTree Project and Woodland Diversity
Rapid onset climate change, and the spread of new pests and diseases are creating unprecedented challenges to the long-term survivability of UK woodlands. This looming threat is becoming ever more tangible, and the need for strategies of resilience building is urgent. Promoting diversification within and amongst woodlands has been identified as one such strategy with the potential for significant, positive impact. DiversiTree is a UKRI-funded project led by the James Hutton Institute which is measuring the impact a more diverse mixture of tree species has on building resilient woodland ecosystems, as well as how woodland managers and others understand woodland diversity, and what they are CURRENTLY doing to promote resilient woodlands. The project also hopes to generate practical advice and results which managers can use to make better informed decisions regarding the species mix of their woodlands, especially with regard to conifers. A key question which often accompanies discussions of woodland diversity is the planting of non-native species within British woodlands. The DiversiTree project is taking an evidence-focussed approach to its assessment and are investigating how ecological resilience interacts with woodlands with different priorities or objectives and what this might mean for the longer-term ecological sustainability of the forests of the UK. In actuality, many native woodlands are rather species poor, and could potentially benefit from a period of managed diversification with native species, non-natives, or a mixture depending on local objectives and context. What is critical here, is understanding the ecological role ANY tree can serve in a complex landscape, and planting in a manner which enhances and strengthens a woodland’s biodiversity. If you’d like to learn more about our work and keep updated with our progress, please follow us on Twitter @DiversiTree_UK (https://twitter.com/DiversiTree_UK?s=20) or email [email protected] with any questions. Seumas Bates (Environmental Anthropologist, Bangor University)
New uses for ‘waste’ plant material.
Many trees emit a scent or fragrance. They form volatile organic compounds (VOC’s), often oils. Pine trees, for example, release pinenes. Such VOC’s contribute to the smell that you may experience as you walk through a woodland. The VOCs contribute to the formation of aerosols. An aerosol is a ‘mixture’ of very small particles (solid or liquid) in air; other examples of aerosols include mist, cigarette smoke, or even car exhaust fumes! Recent research by the University of East Finland has showed that aerosols formed from VOCs can reduce the amount of solar radiation that reaches the earth’ surface, by scattering some of the radiation back into space. [caption id="attachment_40200" align="aligncenter" width="532"] Felling in progress[/caption] Pine trees are often grown in vast numbers and periodically felled for timber and paper making. One by-product of paper-making (by the Kraft process) is turpentine - formed by the condensation and collection of the volatile oils in the wood). The pinenes (α and β) are major constituents of turpentine. ‘Turps’ is used as a solvent to thin oil-based paints, for producing varnishes and as a ‘raw material’ in the chemical industry. α-Pinene was used to make toxaphene (an insecticide, now banned). Pinene can also treated with acetic acid to make a perfume with a pine needle smell. Recently a team of scientists at the University of Bath have found a new use for the by-products of paper production. Using pinene from turpentine, they have been able to make a number of pharmaceutical compounds that can then be made into the painkillers - paracetamol and ibuprofen. They have also successfully made other chemicals from the plant based turpentine, including compounds that may be used to synthesise `beta-blockers (heart tablets) and salbutamol (used for asthma). At present, many pharmaceuticals and other chemicals are ultimately derived from crude oil. Hopefully, this research will ultimately lead to a more sustainable and ‘green’ approach to drug / pharmaceutical manufacture. Biochar is the black residue, consisting of carbon and ashes that remain when plant biomass is subject to pyrolysis - that is, very high temperatures with very little or no oxygen present oxygen. The material that remains is largely elemental carbon. The benefits of converting plant biomass into biochar is that the carbon is ‘locked up’, rather than being released by decay and decomposition into the atmosphere as carbon dioxide. Its advocates claim that when added to soil, it improves soil structure and function, as well as being a form of carbon sequestration.. [caption id="attachment_40215" align="alignleft" width="300"] cocoa fruit[/caption] Various forms of biomass (woody debris, corn stalks) have been used to produce biochar, however, a novel method makes use of ‘discarded’ cocoa bean shells. These are heated to a temperature in excess of 600oC, with no oxygen present. This particular form of biochar is being produced in in Hamburg. The plant, which is one of the largest in Europe, receives a supply of used cocoa shells viably a network of grey pipes from a neighbouring chocolate factory. Apart from its use as a fertiliser, it is possible that it might be used as an ingredient to create a ‘green’ (or more environmentally friendly) form of concrete. The sequestration of carbon is vital if we are to avoid the worst effects of climate change. Global warming has triggered an increase in heatwaves, floods, droughts, and forest fires in recent years; June temperature data confirms it was the planet's hottest on record. Cocoa fruit : courtesy of Pixabay.