Blog - Woodland Web Updates
Woodlands web updates 21
Ancient Trees A recent report has emphasised the importance of protecting and preserving ancient trees. Ancient (veteran) oaks can live in excess of a thousand years, as can Yews. The Bristlecones of California and Nevada may live for some five thousand years ! Such trees represent a massive carbon store; the carbon dioxide from the atmosphere being locked away for a millennium or five! Not only are such trees a significant carbon store but they also offer a home or food for many other species - fungi, epiphytes such lichens & mosses, plus larval and adult stages of insects, birds and mammals. As such they localised centres of diversity that contribute to ecosystem stability. Not only are these trees ‘hotspots’ for species diversity but they are also centres of mycorrhizal activity and connectivity. Mycorrhizae represent the symbiosis between fungi and plant. Plants ‘register’ wounding. When we are hurt, our nerves register the pain through the movement of sodium and potassium ions along the nerves. When a plant is wounded, calcium ions are known to move in response, travelling from cell to cell, and leaf to leaf. However, it is now known (through research at the John Innes Centre in Norwich) that this is not the first response of the plant to physical injury. When cells are wounded they release glutamate, a form of glutamic acid. This travels along the cell was and activates channels in the cell membranes that allow the movement of the calcium ions. A bumblebee pathogen. One of parasites of bumblebees is Crithidia bombi. It is a protozoan (single celled animal) that reproduces in the gut of the bumble bee. When infected with this parasite the foraging behaviour of the bee is impaired, as is its ability to learn. A colony will suffer from increased worker mortality. Now research has shown that floral structure may influence the transmission of this parasite from bee to bee. The length and shape of the petals seems to be a critical factor. If the bees ‘crawls’ in a ‘tube’ of petals, then it may leave behind some faeces. If the bee is infected with the parasite, then it will be present in the faeces. If the flower is then listed by another bee then it runs the risk of coming in contact with and being infected with the parasite. Plants that have flowers with shorter petals / corollas are less likely to have faeces deposited within them, and therefore less likely to pass on the parasite to the visiting bumblebees.
Woodlands web updates : 20
Moss puts a brake on peak flow and flooding. “Moors for the future” have been working in the Peak District to investigate the run off of water after rain. Often after a storm, rain water will run off a hillside unimpeded so that communities downstream in valleys are vulnerable to flooding. Moors for a future have been planting upland areas (on Kinder Scout) with Sphagnum moss. They have planted some 50,000 plants of the moss. Prior to the planting of the moss, the surface might be bare, and rainwater would run straight off. It was found that the moss dramatically slowed the run off of water, and the volume of water discharged from the hillside, preventing rivers from becoming inundated. Each moss plant can hold up to twenty times its own weight of water. The sphagnum moss also protects the underlying peat, so that new layers of material can accumulate - allowing for carbon sequestration. Help from vegetables ? More and more bacteria are now resistant to many types of antibiotics, consequently it is increasingly difficult to treat certain types of bacterial infection / disease. In some cases, this is due to the production of a biofilm. Bacteria grow on many surfaces within our bodies and as they grow and multiply they may encase themselves in a matrix of extra-cellular material that they produce ( as seen in Pseudomonas sp). Research workers at the Ben Gurion University have found that certain compounds from cruciferous vegetables, such as broccoli, can break down these bacterial films. Cruciferous vegetables include Cabbages, Cauliflower, Brussels sprouts, Kale, Radish, Kohlrabi and Mustard. The chemical DIM (3,3 diindolylmethane) was able to disrupt the biofilm. When introduced to an infected, wound, it was found to speed up the healing process. It is hoped that further work will lead to a commercially viable product for the treatment of certain infections. (Thanks to Ulleo on Pixabay for adjacent image). ‘Help Signals’ from oil seed rape. Oilseed rape (or rapeseed, Brassica napus) is a major crop in many parts of the country. It provides an oil and is also contributes to animal feedstuffs and biofuels. Great swathes of the country turn yellow when the plant is in flower during the summer months. These monocultures are ideal for the animals that feed on the plants, these range from insects, to nematodes, slugs and wood pigeons One particular pest of oil seed rape is the Common Pollen Beetle (Brassicogethes aeneus). The female beetles lay eggs in the flower buds of and the larvae develop within the flowers. Both adults and larvae feed on the pollen and nectar in the flowers. Plants have limited means of fighting attackers. They may construct structural defences, as discussed in the woodlands blog, or they may use chemical defences. When bitten by a marauding herbivore some plants emit volatile organic compounds (VOC’s). As the pollen beetles feed, the rapeseed releases VOCs which attract the attention of other insect - notably those that will lay their eggs into the larvae of the pollen beetles. These insects are usually from the same family as bees, wasps and ants - the Hymenoptera (insects with membranous wings and a ‘narrow waist’. The pollen beetle larvae are then ‘eaten’ from the inside by the developing parasitoid larva. This effectively constitutes a form of biological control. Interestingly, the pollen beetles preferred to lay eggs into rapeseed plants plants growing with high levels of N fertilisation, whereas their parasitoids favoured more moderate levels of N fertilization. This work was undertaken at the Estonian University of Life Sciences. Finding the flowers. Research at the University of Exeter has shown that bees can distinguish between various flowers through a combination of colour and pattern. This selectivity is achieved despite the ‘acuity’ of a bee’s vision being quite low (about a 100 times lower than ours) - this means they can only see the pattern of a flower when they are quite close ( a matter of centimetres). The researchers analysed a large amount of data on plants and visiting bee behaviour, and experiments involving artificial shapes and colours. One particular finding was the importance of the contrast between the outside of the flower and the plant’s foliage. This seemed to help bees quickly find their way to the flowers.
Woodland web updates : 19
Shade and stress. Shade (low light intensity) causes plants to elongate, reach up to the light to ‘outgrow’ the competition. Such ‘elongated plants’ are said to exhibit etiolation. However, there is a point when this strategy is counterproductive. The plant simply cannot outgrow its taller neighbours, it is wasting resources and becoming weaker. So plants in deep shade do not generally use this strategy. Deep shade is detected by the phytochrome pigment system and ‘relayed' onto the plant’s circadian clock, the internal ‘daily time piece’. This internal clock has various components and particular genes, some of which have an additional role in suppressing stem elongation (that would normally occur when shaded). Welsh woodlands and insect pollinators. A recent study across many different sites in Wales has revealed the habitats favoured by pollinators such as bees, overflies and butterflies. The research found twice as many insects in broad leaved woodlands as compared to grassland areas. They also found that farmlands without hedgerows had significantly fewer insects. Both hedgerows and woodlands include trees such as oak and maple, which offer varied niches for pollinators. They provide food (leaves) for larval stages, pollen and nectar for adults, plus egg laying sites and shelter. In Wales, there are plentiful grassland areas (mainly due to farming) with woodland only contributing 15% of land cover. However, the Welsh Government aims to plant 180,000 hectares of new woodland by 2050. New woodland will not only contribute to tackling climate change (through carbon sequestration) but will also do much to promote insect biodiversity. Sludge as fertiliser Sewage sludge is commonly spread across farmland as a form of fertiliser (throughout Europe). Sewage sludge is the residual, semi-solid material that is the ‘by-product’ of sewage treatment of industrial and / or domestic wastewater. Sometimes, referred to as biosolids. It is a sustainable / renewable source of nutrients and reduces material going to landfill or incineration. The use of sludge has attracted attention as it can contain: Breakdown products of various medical / pharmaceutical that have been excreted / eliminated from us and / or animals, such as hormones, antibiotics, various drugs Heavy metals such as lead, cadmium, arsenic Industrial chemicals / breakdown products PCB’s, dioxin Now, research at Cardiff University has shown that micro plastics in sludge are a problem; these are plastic particles less than 5 mm in size. It estimates that between 31,000 and 42,000 tonnes of micro-plastics are applied to European soils each year. They are a threat to wildlife as they are easily ingested and can carry / contain toxic chemicals and may pass along the food chain. The UK was shown to potentially have the highest level of microplastics in its soils, followed by Spain, Portugal and Germany.
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Mites and bees. Varroa destructor also known as the Varroa mite is a small, external parasite of the honey bee : Apis mellifera. It is a mite. Mites are small members of the arachnids (8 legged arthropods). The mite(s) attaches to the body of the bee and feeds upon its fat bodies; this weakens the bee. The mite also feeds on bee larvae. Not only that but the mite can act as a vector (‘distributor’) for five different viruses that also weaken the bees. The varroa mite originally was to be found in Asia, and was parasitic on the Asian honeybee, Apis cerana. Sadly, it has now spread to many countries and is responsible for significant infestations of European honeybee hives. Over time, the mites have become increasingly resistant to chemical treatments. Now a program / study by the Universities of Exeter and Louisiana has been selectively breeding bees that identify and remove mites from their colonies [ie. showing hygienic behaviours]. They do this by removing infected larvae from the colony. This is sometimes referred to as varroa sensitive hygiene. Such colonies showed significant reduction in mite numbers and were more than twice as likely to survive winter as compared the ‘standard’ honey bees. The colonies also had reduced levels of three honey bee viruses The study looked at bee colonies across three American states, including California. In the States, beekeepers move thousands of bee colonies to provide pollination services for many different fruit crops (e.g. almonds) in the Spring, thus winter survival of the colonies is vital. Historic rainfall records. was launched in March 2020 (during the 'first stay at home' / lockdown). Members of the public were asked to help record digitally the information on pre-1960 weather sheets. The Met Office archives had some 65000 sheets that contained the ‘scribbled records’ of thousands of weather stations/ weather recorders across the country. Many of these sheets were the records of amateurs dating back decades, many before the foundation of the Met Office in 1854. One such 'recorder' was Lady Bayning of Norfolk, she was an early rainfall observer who took readings from 1835 to 1887. Deciphering the idiosyncratic handwriting could not be done by character recognition software. However, the volunteers rose to the challenge and the task was completed in some 16 days. As a result, now the Met office has: Rainfall readings stretching back to 1836 Data from an increased number of rain guages Identified the driest year on record - 1855 Identified the driest month on record February 1932 Identified the wettest month on record October 1903 Note : [The Met Office was founded by Robert Fitzroy, the captain of HMS Beagle, that carried Charles Darwin on his epic voyage around the globe. Fitzroy essentially established the science of weather forecasting] Trees on the move ? We know that trees can ‘move’. They did so at the end of the last Ice Age (some 12,000 years ago). As the glaciers retreated so trees started to return to the newly exposed soils as the temperature warmed. The discovery of the remains of acorns in archaeological digs, and analyses of fossil pollen records indicates that even oaks colonised areas of the UK at the rate of nearly a kilometre a year. Similarly, Norwegian Spruce colonised areas around the Baltic Sea and the boreal forests grew and expanded - long before humans arrived there. Now we have warming temperatures as we have moved into the Anthropocene. In order to survive changes conditions, plants, like us, have to move. So, like after the ice Age, plants and trees are on the move. Scientists in California have calculated that as a result of global temperature changes, plants need to move northwards (or upwards) at the rate of 400+ metres a year. In the eastern parts of the United States, it has been estimated that trees were shifted north and westward at a rate of 10 / 15 km per decade. The conifers going north. Whilst oaks and birches going west. In Scandinavia, which has experienced significant aspects of global warming, birch saplings are now found higher up mountains, gaining 500 metres in elevation within two decades. Pines, spruces and willows are also growing at higher altitudes than previously. Similar colonisations of hillsides and ‘bare valleys” are seen in Alaska of alder, willow and dwarf birch. Further information here [caption id="attachment_38737" align="aligncenter" width="700"] Busy bee[/caption]
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Beech and climate change. Beech trees are important (ecologically and financially) in the woodlands and forests across Europe. Beech has a wide distribution from Southern Europe up into Scandinavia. However, the beech has a relatively shallow root system and this makes it susceptible to drought. In recent times, as a result of climate change, extreme weather events such as drought have become more common. Analysis of beech tree rings (from 5000+ trees) across Europe suggest that whilst those Sweden and Norway are growing quite well those in Southern Europe are not, in fact growth may have declined by as much as 20%. Current climate projections suggest that beech growth / productivity in southern areas may decline further, with increasing mortality. Warning signals. Many animals are able to send signals to other members of their species warning them of imminent danger, such signals can be warning sounds or ‘scents’. The scents may be in the form of pheromones, essentially ‘airborne hormones’. Now there is growing evidence that plants may be able to act in a similar way. For example, if mint leaves are damaged by a insect herbivore attack, then field mustard and soybean plants growing in the vicinity respond to the volatile chemicals released by the mint and activate their leaf defence systems (this often involves creating an unpalatable taste). The volatile compounds released (during damage) are ‘oils’ or terpenes, like β-Ocimene. β-Ocimene has a sweet, woody fragrance but it is not clear how it stimulates other plants into activating the genes for their defence mechanisms. Research is underway at the Tokyo University of Science. Lead and Birds of Prey. Birds and Prey feed upon flesh they scavenge (like the entrails of deer, or dead pheasants) or from animals they capture. The trouble is that often this flesh is riddled with bits of lead shot. Lead is a poison, and is not easily eliminated from the body. Animals injured by lead shot may suffer a slow and agonising death. Those that feed upon them also accumulate lead in their bodies, which affects their physiology and behaviour. Now Cambridge based scientists have studied the lead levels in a variety of birds of prey. They looked at lead levels in the livers of some 3000 raptors. Birds, like eagles, are worst affected as they are long lived, breed later in life and rear relatively few young per year. For a number of species, they have been able to estimate the % reduction in population size that the lead is responsible for. Species Estimated % loss of population White tailed eagle 14 Golden Eagle 13 Griffon Vulture 12 Red Kite & Western Marsh Harrier 3 Buzzard populations are estimated to be 1.5% smaller, which may not seem much but it equates to the loss of some 22,000 birds. Lead is still used in shotgun cartridges, many pheasants are still killed with lead based ammunition, despite requests to hunting groups to switch to non-toxic gunshot (by 2020). Full details of this work can be found here. Warmer autumns and butterflies. Green veined white butterflies are common in the U.K. and Europe. Researchers in Sweden have been looking at how they might respond to warmer and longer autumn weather. Under laboratory conditions, they exposed the chrysalises (over-wintering stages) of the butterfly to warmer autumnal conditions. They found that the chrysalises used more energy and lost more weight under these conditions, and were less likely to survive to the adult / imago stage in the following Spring. With global warming affecting our climate, it could be that populations of this butterfly could struggle as time passes.
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LASI is the Laboratory of Apiculture and Social Insects at the University of Sussex. It is particularly noted for its research work on bees. Recently, Dr Balfour and Professor Ratnieks have published a study on the rôle of certain 'injurious weeds'. Five of our native wildflowers fall into this category : Ragwort (Jacobaea vulgaris), Creeping or Field Thistle (Cirsium arvense), Spear or Common Thistle (Cirsium vulgar), Curly Dock (Rumex crispus), and Broadleaved or Common Dock (Rumex obtusifolius). They compared the ragwort and the thistles with plants like red clover and wild marjoram (often encouraged / sown on field edges etc).. They found that the 'injurious weeds' were particularly 'effective' at attracting pollinators, not only did they they attract greater numbers of pollinators than clover etc, but also a greater range of pollinator species. This was ascribed to the open nature of their flowers and their generous nectar production. This brings into question the control of species like the ragwort, as it is clearly important to pollinators (as are some 'botanical thugs' - like brambles). Ragwort contains chemicals that are toxic to livestock, causing liver damage; it has been blamed for the deaths of horses and other animals. At the Smithsonian, Kress and Krupnick have analysed the features of some 80,000+ species of plants to see how they might fare in the Earth's changing climate (the Anthropocene). This may seem like a large number of different plants, but represents approximately only 30% of the known species of vascular plants. There is not enough information of the remaining species to make a reasonable guess as to how they might react to climate change; a reflection on how little we actually known about our 'botanical resources'. Sadly, they conclude that more plants will lose out than win. Particularly at risk of extinction are the Cypress family (which includes the redwoods and junipers) and the Cycads, whereas black cherry might be a winner. As was reported previously in the woodlands blog, there is a difference between the leaves of the redwoods found at the top of the tree and those lower down. Those at the top are small, thick, and fused to the vertical stem axis; this fusion of leaf and stem creates a relatively large volume of tissue and intercellular space that can store water. The leaves in the lower part of the crown by comparison are large, flat and horizontal to the stem axis. Now scientists as the University of California (Davis) have further investigated the role of these leaves. They now believe that the different leaf forms help explain how the exceptionally tall trees are able to survive in both wet and dry parts of their range in California. In the rainy and wet North Coast, the water absorbing leaves are found on the lower branches of the trees. In the Southern part of the redwoods range, the water collecting leaves are found at a higher level to take advantage of the fog (and rain, which occurs less often).
Woodlands web update 15.
Lichens losing ? Sitting on the bark of many trees and on the surfaces of fences and walls, there will be lichens. They are there in summer, winter, spring and autumn. Lichens come in an amazing variety of shapes, sizes and colours. Some can grow in extreme environments such as the rocky summits of mountains. Such lichens grow slowly and may live for hundreds of years. Lichens are rather unusual in that they are an amalgam of two (or occasionally three) organisms : a fungus and algae. They are symbiotic systems, where the partners of the association work together for mutual benefit. The fungus makes up the bulk of the lichen’s structure (known as the thallus), but the algae (green algae or cyanobacteria) are essential as they can photosynthesise and provide the organism with carbohydrates. Lichen covered tree One of the most common algae found in lichens is a species known as Trebouxia. It can exist in association with a fungus to form a lichen, or as a free living organism. If the Earth’s warming continues at the present rate, it may well be too hot for certain species of Trebouxia to survive (in their normal range). Dr M Nelson of the Field Museum (Chicago) has looked at the adaptability of Trebouxia species and suggests that it could take hundreds or thousands of years for Trebouxia species to cope with the temperature changes that we are currently experiencing. These algae may well lose out in the evolutionary race to cope with climate change. This would, in turn, affect many different species of lichen. Lichens are important in arctic tundra ecosystems, where they together with mosses and liverworts make up the majority of the ground flora. They contribute to food chains, for example, reindeer moss is not a moss but a lichen. Lichens are also pioneer species - they can colonise bare rock and contribute to its weathering (their exudates chemically degrade and physically disrupt the minerals). Lichens may be used by birds as nesting material. Hedgehogs. Rural hedgehog populations are still in decline, dropping by 30 to 75%, this is in contrast to urban populations that are ‘steady’. Though urban populations suffer mortalities on the roads, well managed urban areas, parks and wildlife-friendly gardens provide refuges for hedgehogs. The loss of hedgerows and diminishing field margins is contributing to the decline of rural populations. Land of Plenty report The WWF-UK has produced a report entitled “Land of Plenty”, which addresses some of the problems that the UK faces now and in the coming decades. There are many reports relating to the loss of plant and animal species and the degradation of particular ecosystems (flower-rich meadows, peatlands, salt marshes etc). Sadly, much of this damage has been associated with the expansion of our farming / food production systems; indeed some 70% of the land is involved in agriculture. The WWF report outlines how a move towards regenerative farming / agriculture can significantly reduce CO2 and methane emissions, reduce pollution (from fertilisers) and help with biodiversity and resilience. Such changes would (in time) help limit farmers’ exposure to extreme weather events that affect crops / harvests. One of the many suggestions in the report is the expansion of ‘woodland creation programmes, focussing on potential for broadleaf and native species’. The focus would be on natural regeneration in the first instance, but supported by active tree planting. Full details of the report available in PDF format here. Drought, bark Beetles and fires. Woodland recovering from a fire The Cameron Peak Fire in the Rocky Mountains of Colorado and the Creek Fire in the Sierra Nevada of California burned through forests where large number of the trees had been killed by bark beetles. Warmth favours the bark beetles. Mountain pine beetles had killed millions of lodgepole pines. A dead tree does not take up water, it dries out. The drying out was ‘helped’ by the drought that the West Coast has experienced in recent years. The fires burned with incredible ferocity. In the case of the Creek Fire, the plume reached some 50,000 feet up into the air. The fires were the result of Drought / climate change Bark beetle infestation Large numbers of dead, dry trees Consequently, large amounts of energy-rich dry biomass Full details of the factors behind the forest fires here. Drought is a major ‘stressor’ affecting many ecosystem across the globe. To understand how drought affects different ecosystems, DroughtNet is working with a number of existing projects and the International Drought Experiment (IDE). A recent experiment at the University of Florida demonstrated how drought-stressed pines did not grow as well, and when faced with an invasive species and fire - they were much likely to succumb than a healthy tree.
Woodland web updates 14.
Reports on pollinators. Research by workers at the University of Reading and the Centre for Ecology and Hydrology has shown that various ground level pollutants (nitrogen oxides and ozone) have significant effects on the pollinating activities of bees, moths, butterflies and hoverflies. The number of flower visits by these insects declined, as did the level of pollination and seed production. The University of Göttinggen has published a study that bumblebees need a diverse pollen diet, collected over a variety of habitats. A varied pollen diet contributes to better colony growth, more offspring (particularly young queens). It also helps offset the effects of infestation with wax moth larvae. Wax moth caterpillars feed on nest debris, but as they grow they switch to feeding on the food stores and even grubs / larvae, effectively destroying the nest. Recent work by an Irish postgraduate student on insect pollinators in Dublin suggests that a “less is more’ approach might be effective when it comes to natural green areas in cities. Emma King looked at the pollinators present in Areas of planted meadows or sown with wild flower mixes. Areas with reduced mowing that were allowed regenerate naturally. She found that though insects like bumblebees and hoverflies were more frequently recorded in planted meadows, statistically there was no significant difference in the numbers; and the community of pollinators was similar in both types of green areas. The advantage of allowing green areas to develop naturally is that it reduces labour and material (seeds) costs. They may take a bit longer to establish a diverse flora but they will offer resources to pollinators. Such green spaces promote habitat connectivity within the urban environment. Sunflower update Work by staff at the University of British Columbia has revealed that sunflowers (like many other flowers) helps bees to visit by invisible (to us) ultra-violet patterns - usually in the form of a ‘bulls-eye’. They observed that sunflowers growing in drier conditions had flowers with larger UV ‘guides’. Furthermore, it was found that a particular gene was responsible for the nature of the bulls-eye pattern, and this gene was also associated with the production of flavonol compounds. Quite how the gene and the production of flavonols is related to the capacity of sunflowers to retain water is not known. [Full details of the work of Dr M Tedesco et al here].