Woodlands web updates 11
Hungry caterpillars. Many insects feed upon the leaves of the canopy in woodlands and forests. They can vary from aphids, leaf miners, sawflies to butterfly and moth caterpillars. Every few years there are significant ‘outbreaks’ of particular moth caterpillars, for example, gypsy moth caterpillars. These caterpillars feed on the leaves of many broadleaved trees but are 'partial' to oaks [and poplars (Populus species)] in woodland / forest situations. When their numbers of high, they can cause significant defoliation. A study undertaken by researchers at Cambridge has revealed that moth outbreaks can have significant effects on the surrounding ecosystem(s). As the numbers of caterpillars are so high, they eat large amounts of leaf material. This has a number of consequences The amount biomass in leaf fall in the autumn is reduced The caterpillars convert the carbon-rich leaves into nitrogen-rich frass. The caterpillars are not very good at using the leaf nitrogen for their own ends. Frass is the excrement / faecal material produced by the caterpillars. This frass can pass into streams / waterways and end up in lakes and ponds. Once in the lakes etc, it changes the chemistry of the water and it favours the reproduction of bacteria that release carbon dioxide. This happens at the expense of the algae, which remove carbon dioxide from the atmosphere. The amount of carbon entering streams and lakes is reduced in caterpillar outbreak years. Caterpillar outbreaks significantly affect the carbon and nitrogen cycles in woodlands and associated freshwater systems. Details of the work (which focused on forest and lake systems in Canada) can be accessed here. Air pollution and wood burning stoves. Tiny particles called PM2.5 (released from a variety of sources, such as road traffic) pollute the air. They are harmful to our health as they can pass into the lungs and out into the blood stream. They then circulate around the body and end up in various organs. One source of these tiny particles is the burning of wood in wood burning stoves. One recent study has suggested that wood burning may account for some 40000 early deaths in Europe each year! The biggest single source of PM2.5 air pollution in the U.K is domestic wood burning, which is said to produce three times as much pollution as road traffic. The situation is similar across Europe. Only 8% of the population use wood burners New wood burning stoves are said to be more environmentally friendly but they still emit more tiny particle pollution than an HGV truck. The ecodesign standard developed by the EU allows wood stoves to emit 375 g of PM2.5 for every GigaJoule of energy produced. By contrast, an HGV can only release 0.5 g per GJ. HGV have filters and catalytic converters that capture / reduce pollution. The burning of wood in stoves involves many factors, including air flow, fuel quality / dryness and the amount of fuel being burnt. Full details of the European Environmental Bureau report “Where there's fire, there's smoke. Emissions from domestic heating with wood” can be found here . Bees, weather and disease. It is well known that weather has a direct effect the foraging ability of honey bees, now it is known that weather / climate also affect the incidence of disease in hives. A study undertaken by Newcastle University has revealed infection / disease in hives is affected by climatic variables. For example, varroa mite infestation increased as climatic temperature increased, but was reduced during heavy rainfall and wind. Full details of this investigation can be accessed here.
Drought and pollinators
Climate change is affecting all parts of the world, from the melting of the ice caps in Antarctica, to droughts in Australia and California. On a more local level, we may see changes in our rainfall pattern. Certainly for many parts of the UK, it has been a very dry start to the Spring, coupled with some very cold nights. Cold and dry weather affects plant growth in significant ways. Warmth is needed for a plant’s enzymes (catalysts) to work, speeding up reactions and allowing growth. Similarly, if water is in short supply, growth is stunted; plants do not realise their full ‘potential’. They are smaller overall as is the number and size of flowers that they produce. Flowers attract visitors by colour, size and scent; or combinations thereof. Smaller and fewer flowers, in turn, have ‘knock-on effects’ for their pollinators - bees, bumble bees, hoverflies etc. The effects of drought on pollination has been recently investigated by researchers at Ulm University in Germany. They studied the effect of drought on field mustard (aka Charlock) : Sinapsis arvensis. This is an annual plant that is to be found in fields, waysides and field margins across Europe. It has bright yellow flowers, with four petals. It is visited by many different pollinators (it cannot self-pollinate). The researchers compared the number of visits by bumblebees (Bombus terrestris) to drought-stressed plants to well-watered ones. The data showed that as the number and size of the flowers decreased so did the number of pollinator visits. [caption id="attachment_21589" align="aligncenter" width="600"] Bumblebees also favour the teasels[/caption] The ‘attractiveness’ of the plants / flowers to pollinators was reduced, and it is possible that the smaller flowers were more difficult for relatively large pollinators (like the bumblebees) to ‘deal with’. If pollen movement is reduced, then fewer fruits / seeds will be set and (insect pollinated) plant populations could decline. The effects of reduced rainfall and water stress need to be considered alongside the declining number of pollinators. The reduction in pollen movement has lead some to speculate that it might lead to a selective pressure for self-pollination / self-fertilisation, with plants dispensing with the need for visiting insects. Other Woodlands blogs have reported on the falling numbers of insects / pollinators. Featured image : garlic mustard.
The Wood that Built London – a History of the Great North Wood – CJ Schuler
A magnificent book about a woodland which dominates south London, even though only pockets of the woodland remain. The author pulls off the trick of using the story of the Great North Wood to relate centuries of social history and much about woodland ecology. It's gritty, too, and it soon becomes apparent that Christopher Schuler doesn't just volunteer in Dulwich Woods, a sizable remnant from the Great North Wood, but he also loves the woodland. The Great North Wood was really big - several thousand acres in extent - stretching seven miles from Croydon to Deptford and even the remaining segments run from Dulwich to Norwood (a shortened version of "North Wood"). It was also an important resource for many centuries mostly for firewood, building timbers and of oak trees for naval building. But Schuler demonstrates the richness of its history and the contradictions in the way it has been managed - in the 18th century cash payments were made by the parishes to anyone bringing in badger heads or other "vermin", which we would now consider valuable wildlife. One tradition which Schuler explains went on for centuries, was the "beating of the bounds" where on a set day on April (25th, Rogation Day) every year the Parish boundaries were followed on foot by a formal group. The members of this group would literally beat sticks against trees along the boundaries and mark some by carving crosses into them. In order to make sure the boundaries were remembered they made sure that old men were included who remembered earlier "beating of the bounds" and teenage boys who would be expected to remember the boundaries for decades to come. In order to help them remember more clearly their hands were sometimes pricked at key points so that they would be more likely to recall the spot. Often there was merriment and drinking on such occasions but there was also a seriousness as at certain notable points the priest would say prayers. One of the more famous spots was the Vicars Oak at the end of the road which is now called Crystal Palace Parade. This was a tree on the boundary of three different parishes and being at the top of a ridge was visible for miles around. [caption id="attachment_36450" align="aligncenter" width="650"] The North Wood[/caption] Many bodies influenced the course of the woodland - for a long period it was forbidden to cut any oaks for other than naval use in order to ensure the navy had enough timber which could be moved to a navigable waterway. The dominant owners over the centuries were various church organisations, although the freehold of most of Dulwich Woods now belongs to the Dulwich Estate and Southwark Council. Both organisations tried to build housing on the woodlands in recent decades but this has been successfully resisted by conservationists, and the London Wildlife Trust (LWT) now manages most of the Dulwich Woods part of the Great North Wood. Many people volunteer for the LWT and some have fought hard to stop oak trees being felled for bridge repairs or other expedient reasons. Christopher Schuler's "The Wood that Built London" will be the defining work on the Great North Wood for a long time to come. It was through the industry of London's labourers, as Schuler states, that "the Great North Wood fuelled - quite literally - the growth of the great city that would ultimately consume it."
November’s Fungi Focus – The Earpick Fungus (Auriscalpium vulgare)
Not all mushrooms have gills. Some, like the boletes, have pores on the underside of their cap. Others have arrays of downward-facing spikes that look like teeth. This third category are described as hydnoid, and include such aptly named species as the Wood Hedgehog (Hydnum repandum) and this month’s fungi focus, the Earpick Fungus (Auriscalpium vulgare), also known as the Pinecone Mushroom or Conetooth. These teeth, like gills and pores, constitute the ‘hymenium’, the fertile surface in basidiomycetes fungi on which spores develop and from which they are released. Look under a microscope at a mushroom gill or the inside of a pore or the edge of one of these teeth, and you will see it coated with thousands upon thousands of tiny spore-bearing structures known as basidia (as opposed to the other group of fungi, the ascomycetes, where the spores develop and are fired out from tubelike structures known as asci). These gills, pores and teeth are nature’s ingenious way of maximising the spore releasing area that contain the basidia. Two toothed fungi species - The Ochre Spreading Tooth and the Fused Tooth It should be pointed out that not all of the toothed fungi are of the mushroom-shaped cap-and-stem variety. There are also bracket and resupinate hydnoid types, like the Ochre Spreading Tooth (Steccherinum ochraceum) or the leaf litter-dwelling Fused Tooth (Phellodon confluens). However, all these examples point to the important rule I always emphasise when trying to identify fungi or taking a photo for someone else to do the job for you – always look underneath! To be honest, you’d find it pretty hard to mix up the Earpick Fungus with anything else at first glance anyway. Not only does its felty brown kidney-shaped cap, perched atop a slender but bristly stem, with row upon row of downward-pointing teeth on its underside, make it look like some weird alien monster you’d expect to see in a film like Little Shop of Horrors or in a Pokémon game. Its identity is also defined by its specific substrate of pinecones or other conifer-related litter. Earpick Fungus That is if you notice them in the first place. Earpick Fungi don’t tend to get much larger than 5cm in height and their caps reach around 3cm across at their widest point – as mentioned, the caps are kidney-shaped rather than circular, with the stem on one side of it rather than the centre. Their dun colouration makes them blend in with their conifer cone hosts, so you’ll probably only find them if you’re actively looking. But get down to ground level and look closely and you’ll see nothing else like these stunning little things. Just how unusual are they then? There seem to be a number of other species in the Auriscalpium genus (the Latin name literally translates as ‘ear pick’), according to its Wikipedia entry, but Auriscalpium vulgare is the only one found in the UK thus far. Indeed, it is considered the type species for Auriscalpium - the first of its kind discovered (in 1821 by the British mycologist Samuel Frederick Gray) to which all others in the genus are compared. Earpick Fungus The First Nature entry describes them as “infrequent and apparently localised”, which could mean that they are under-recorded because they are so inconspicuous and that the few people who do know where to look and what to look for are the same ones recording their discoveries on general websites like iRecord or more fungi specific ones like The Fungus Conservation Trust database. Fungi recording being the piecemeal process that it is, they may be a lot more widespread than we might assume, and indeed, photos turn up on various specialist fungi social media groups fairly regularly. This is not to say I would personally pick them, even to take home for closer analysis or to look at spore samples. I know there are plenty of foragers out there who are beholden to the mantra that a mushroom is only the fruiting body of the larger fungi organism and therefore picking them does no harm. As they argue, the rest of the mushroom is in the form of an expansive network of mycelium that is hidden underground, so it is essentially the same as picking an apple from a tree. Clearly the logic is flawed for both the Earpick Fungi and many other species, even if it did make a for a particularly choice edible (which by all accounts it doesn’t). Clearly the mycelium of this particular specimen is limited by the edges of its pinecone substrate, and therefore the ratio of its fruitbody size to the entire organism can only be very low. Earpick Fungus In other words, the effort that the Auriscalpium mycelium in the pinecone channels into putting up a single fruitbody must be considerably more than that of, say, an ectomycorrhizal species like a Russula or Agariuc, where the mycelium forms an expansive network stretching around and beyond the roots of its host tree. Therefore picking it removes a substantial part of the organism, if we assume the fruitbody to be an inseparable part of the organism. If you do come across one, it is probably best to leave it there intact to continue releasing its spores rather than picking it from the cone and risking killing it off entirely.
Growing Osier for Basketry.
Along with my wife Marie, we purchased a 3 ½ acre semi ancient woodland in South Wales from woodlands.co.uk in April 2020. The site has a gentle slope from a country lane down to the river Rhymney, we have 2 springs, a stream, a wide variety of broadleaf trees, shrubs and a small amount of pine. Much of the site had been neglected for many years and so with help and advice from others and a great deal of hard graft by Marie and I we are bringing the site back to a sustainable future. It is a delightful place to be, family and friends all enjoy spending time there and I don’t think I have ever been to the woodland without seeing or discovering something new. We made a decision early on that an open area next to the river would be a good place to grow willow but we also wanted to utilise some willow for basketry. We had experience of neither. The river can breach its banks and wash over the area occasionally although this is generally very short lived. Although the rest of the woodland will be maintained with native species, the willow area is an experiment and we decided to plant a variety of species for basketry, some of these are non-native. We read a great deal about varieties, planting and harvesting and decided on the varieties we wanted to grow. A very useful book titled Willow by Jenny Crisp gave us a lot of helpful information and ideas. We based our choices around colour, they range from golden brown to yellow, red, green and black. Each variety will grow to different lengths in the same year once established, some as much as 17 feet. We searched on the internet for suppliers of cuttings for planting and were very fortunate to find a supplier, https://hattonwillow.co.uk/ based only a few miles away in Caerphilly. Hatton Willow is run by a Sarah Hatton*, she has a plantation with 1000’s of willows and supplies cuttings for planting and basketry, runs basketry classes and makes various commissions as well as the odd appearance on 'The Repair Shop' and 'Country File'. The plants are supplied as rootless cuttings, about 12 inches long in the winter and need to be planted between November and March. You are advised to lay weed suppressant material and to push the cuttings through this into the ground. If like us you are growing for harvesting, each row is planted 60cm apart and the cuttings 30cm to 60cm apart depending on the variety. This close planting ensures that the sticks grow straight and long and can be easily harvested the following year. We ordered 100 cuttings, 10 of each variety so the area taken up is relatively small. 100 plants won’t give us enough willow to go into production but supplemented with some bought sticks will give enough eventually to make some items for our own use. Once the leaves have dropped, we will cut this years growth back, some of which will become cuttings for new plants and over the years as the plants produce more sticks, we will have more to work with. The above image shows the growth on a few of this year’s saplings. Not as vigorous as we had hoped but next year they may establish better. With our willows in the ground, we booked a course at Hatton Willow and used some of the £300 funding provided by woodlands.co.uk as part of our purchase to fund the course. The session taught us how to make a trug, the courses just span a day, all materials and tools are supplied and at the end of the day you come away having learnt enough of a new skill to repeat the work, an understanding of the material and expanded your knowledge and created your own hand-made basket. What Next for us? The options are endless, willow hurdles for our allotment, Christmas wreaths, nesters for birds, green willow sculpture, who knows, we’ll keep you posted. Marie and Marcus Beard. * Sarah runs her courses at the Nantgarw China Works, a venue worth a visit in it’s own right. Osier : Willows, also called sallows and osiers, from the genus Salix, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere.
Thomas Meehan : American autumnal colours
The changing colours of the leaves in autumn is a phenomenon that affects the vast majority of deciduous trees (and some conifers, eg. Larch). The leaves change from green to various shades of yellow, brown, orange, red and even purple. The nature of these changes has been the topic of a previous blog. What is interesting is that this colour change is particularly marked in the trees of the North Eastern region of the United States. Indeed, bulletins are published listing the best places to see the myriad of colours that the trees display. This difference in the colours of American and European trees was commented upon by Thomas Meehan, back in the nineteenth century. Meehan first worked as a gardener at Kew but later moved to Philadelphia (where he is credited with saving Bartram’s Garden). His botanical studies led to him being the editor of The Gardener’s Monthly, writing articles for various newspapers and authoring 'The Native Flowers and Ferns of the United States'. In 1881, Meehan noted in a paper presented to the Proceedings of the Academy of Natural Sciences of Philadelphia, (Vol 33) that the intensity and variety of autumnal colours was much greater in the States than in Europe. He suggested that the difference might be due to the “American light” and that European trees might (after many generations) adapt to this light and then show similar colours. Recently, Renner and Zohner* have investigated this difference. Their paper(s) offer a number of observations / findings: American trees start to break down their chlorophyll earlier in autumn than European trees, so the period in which the leaves operate as photosynthetic 'factories' is shorter. The earlier onset of senescence means they are at greater risk of light mediated damage in the bright days of early autumn (particularly if coupled with cold nights). Trees growing at a particular latitude in Eastern North America receive significantly more light than trees growing at the same latitude in Europe. North American trees react differently to the shorter days of autumn that European trees - when grown in the same area / garden. A greater percentage of North American trees produce anthocyanins - which give the red and purple colours. Anthocyanins absorb light over a wide range of wavelengths. They act as a sunscreen, protecting the leaves at a time when they are undergoing rapid and complex changes that allow them to export valuable nutrients / resources to other regions. It would seem that Meehan’s comments about the ‘American light’ were remarkably prescient some 140 years ago. Renner and Zohner’s detailed papers are available here : https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/nph.15900 https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/416178/nph.16594.pdf?sequence=3&isAllowed=y [caption id="attachment_36385" align="aligncenter" width="650"] Thanks to Oliver for this photo of autumn colour at Westonbirt[/caption]
woodlands web updates 10.
Bees and solar parks As the country tries to move towards carbon zero, so we see more and more solar parks / farms ‘springing up’. Whilst they do create clean energy, they also take up a lot of land, and it is important to see if such solar parks can offer other commercial or environmental benefits. One suggestion is to place honeybee hives on such parks. The bees could provide a pollinating service to surrounding crops / farmland. Researchers at Reading and Lancaster Universities have studied detailed land cover maps / crop distribution patterns to estimate the economic value of deploying honeybees in solar parks. Their investigations suggest that a variety of crops from oil seed rape, soft fruits to apples and pears could benefit from such an arrangement. The benefits would vary across the UK, with the benefits being greatest in the East and South of the country. Care would need to be exercised though to ensure the placing of hives did not disturb the foraging of wild pollinators, such as carder bees, hoverflies etc. Are plants sulphur deficient? Much has been written about the importance of plants nutrients, especially NPK; that is to say nitrogen, phosphorus and potassium. However, little is said about sulphur. However, researchers in Groningen, Graz and Cologne have been looking at the effects of sulphur deficiency, particularly in relation to the colour and shape of the flowers formed. The work focused on Brassica rapa, a member of the mustard family. When it was subject to ‘mild’ sulphur stress (by limiting the sulphate in the growth medium), the flowers that formed were smaller and paler - not the usual bright yellow. They were also likely to be mis-shapen. Colour and shape are features by which pollinators recognise flowers and then visit them. Pollen production by the flowers was also affected; smaller pollen grains were formed. This may in turn affect the pollinators who visit the flowers foraging for food. In the relatively recent past, sulphur deficiency may not have been a problem due to acid rain, which would percolate through the soil, forming sulphates. [In the twentieth century, acid rain formed as a result of the release of sulphur dioxide (and nitrogen oxides) into the air through the burning of fossil fuels. However, various clean air acts have ensured that there is now much less SO2 in the air.] Annual rings, water availability and earthquakes. Christian Mohr (scientist from the University of Potsdam) was studying the transport of sediments in rivers in Chile in 2010 when a massive earthquake shook coastal areas of the country. When he was able to return to his studies, he noticed that streams in the valleys were flowing faster. He reasoned that this was because the earthquake has literally shaken up the soil, so that it was now more permeable and ground water could more easily flow down from the ridges. As a result of increased water supply, he thought that trees down in the valleys would grow more than those on the ridges. He and colleagues drilled out plugs of wood from valley trees and ridge trees, and back in Potsdam they examined the tree rings under a microscope. They also looked at the uptake of different isotopes of carbon as a measure of photosynthesis. They found that trees from the valley floor experienced a small but noticeable growth after the earthquake, and this lasted for weeks or months, whereas the trees of the ridges grew more slowly. It is possible that analyses like these, when combined with other information, could help identify significant historic disturbances. Rising temperatures. Recent years have seen periods of very hot temperatures, Such extreme weather events have been seen not only in the UK but across the globe (Arizona , Victoria Australia, Indonesia). Extreme heat (and drought) have been known throughout history, but it would seem that extreme events are now more common. The first two decades of this century are among the warmest on record; this warming is associated with increasing levels of greenhouse gases (due to human activity). Prolonged heat is not without its effects on us, it leads to sweating, teaches, fatigue, dehydration and heat exhaustion. The very young and the elderly are most at risk from ‘heat waves’. A 2003 heatwave across Europe is said to have caused several thousand 'excess' deaths’, mainly of the elderly. Even gradual but sustained warming of the climate can have its effects. For example, Silwood Park (Imperial’s research station) has commented that though it is now November, they have not recorded a single frosty night - normally they would expect to have three in a ‘normal’ October. Snowdrops are appearing earlier, and some migratory species are changing their pattern / timing of migration. Across the world, different species are being affected in different ways. Thick billed murres (type of guillemot, found in and around the Hudson Bay) have a high metabolism to deal with the cold waters into which they dive - they are cold adapted animals. On warm days (when the temperature is 21cC or above) they are dying whilst sitting on their nests - incubating their eggs. They struggle to keep cool, if they spend more time in the water then they leave their eggs exposed to predators (like gulls and arctic foxes). Similarly boreal and arctic bumblebee species are sensitive to heat stress, succumbing to stupor; other work indicates that some European / mediterranean species are now to be found in areas of the arctic circle - as a result of changing climatic ‘norms’. Wild dogs are adapted to deal with heat, but if the temperature goes beyond a certain point they stop hunting, consequently their pups / offspring are less likely to survive. Warming temperatures not only affect animals but they also contribute to the increasing number of harmful algal blooms (in lakes and off shore regions). These blooms can be dangerous to many animals (including humans) and when they die back they ‘suck’ oxygen out of the water - creating ‘dead zones’. One species of alga (Karlodinium veneficum) which is known to produce toxins has been shown to acclimatise to higher temperatures (up to 30cC). As climate change and research continues, we will no doubt see further examples of how animals and plants are being affected by changing temperatures / climate .
Mosses in woodlands
As we move through Autumn, the leaves of deciduous trees have ‘done their job’. Their capacity for photosynthesis dwindles (as does the light and temperature. In fact, the leaves become a ‘liability’ to a tree, in that they would make use of the reserves that have been stored away. Also, the leaves offer resistance to the winds of winter so a tree is likely to sustain damage. If branches are lost from the stem, then bacteria and / or fungi could enter. The leaves are ‘discarded’ as Autumn progresses. The green colour of the chlorophyll is lost and other colours emerge - reds, oranges and yellows. These colours are associated with different pigments, the carotenes, xanthophylls and the anthocyanins. As the leaves are lost so the trunk and branches becomes more apparent, but they are not necessarily ‘naked’ - devoid of cover. Indeed, walking through a woodland at this time of year, one is often struck by the abundance of mosses. Tree trunks are often laden with ‘carpets’ of moss and their branches bear ‘decorations’ of many different mosses. Beneath the tree, there is often a soft, spongey layer of mosses. Mosses are bryophytes. They are ‘simple’, non-vascular plants ; that is to say they do not have sophisticated transporting tissues (of phloem and xylem). Nor do they have true roots, instead they have structures called rhizoids (which may be uni or multicellular). They live in moist places, indeed they are dependent on water for their reproduction. Mosses or rather their ancestors were some of the first plants to colonise land (which was the rather inhospitable rock of the Ordovician period), previously there were only algae in the seas. Mosses develop sex organs, The male organ is called is called an antheridium, it produces male gametes that can move by means of a flagellum. These gametes swim in a film of water towards the female organ (an archegonium). When the male and female gamete fuse, the structure grows to form a sporophyte. This eventually produces a capsule, which releases spores that grow on to form a new generation. Mosses seldom grow to any great height, mainly due to the absence of supporting mechanical tissue but they can form extensive mats in damp, shady places (as can liverworts). These mossy mats can in some situations prevent soil erosion, and in others allow the accumulation of humus and soil enrichment / formation. An extreme example of the accumulation of mossy material I can be seen in the case of the moss Sphagnum. Sphagnum is unusual in that can hold many times its own weight in water; because of this absorbency, Sphagnum was used as a wound dressing in WW1. It grows in acidic, marshy conditions, often forming a sphagnum bog. The low fertility and cool climate result in slow growth of the Sphagnum (and other plants). The decay of dead plant material is even slower (due low oxygen levels). Hence, peat forms and accumulates. Large areas of the land can be covered to a depth of several metres with peat. Peat bogs are a very effective means of carbon sequestration, locking away carbon for hundreds iff not thousands of years. Unfortunately, many have been drained and allowed to dry out and / or the peat cut from them as a form of fuel. When peat areas are drained (channels are cut through the peat), they degrade and dry out. Then, they are then at risk of burning as has been seem in recent years -for example, in the U.K (Saddleworth Moor). 'Mossy ball' and 'autumn leaves 'photos - thanks to Art Symons.