Blog - Woodland Web Updates
woodlands web updates 16
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].
Woodlands web updates : 13
Wetlands. In the past, many areas of wetlands have been drained and ‘dried out’. Now it is recognised that this is counter-productive in terms of carbon storage / sequestration and biodiversity, so there are now measures to restore wetlands. The hope has been that restoration of wetlands will do much to restore the variety of plants and animals (and help carbon storage). However, research by the University of Copenhagen suggests that such projects might be ‘struggling’. The study examined ten wetlands (near the River Odense) that were restored between 2001 and 2011. The restoration involved the removal of drains and ditches, and allowed streams to meander again instead of flowing in ‘straight channels’. The aim of the project was primarily to reduce the leaching of nitrogen and phosphorus from adjacent farmlands, and hope to see greater diversity of plants (e.g. marsh orchids, globeflower, tussock-sedge and ragged-robin). The ‘restored’ wetlands were botanically poor (whether restored in 2001 or 2011), they had only a quarter of the plant species compared to natural wetlands. This may be due to the continued input of nutrients (from agriculture), which encourages species that are ‘nutrient hungry’ at the expense of others. the ‘difficulty’ of wetland species to disperse from one area to another. It may be that future restoration programs will need to include planting / seeding of additional wetland species. It has been suggested that it could take the best part of a hundred years for the restored wetlands to resemble natural wetlands. Redwoods and relatives. Previous posts have talked about the special features of the giant redwoods (their height, age etc). Over the last 150 years, they have ben subject to the pressures of commercial logging, clear felling and more recently high intensity fires. Indeed, the fires have been of such an intensity that seed banks in the soil have been destroyed. Now they have been subject to genomic analysis, that is their DNA has been analysed and sequenced. The first conifer genome to be sequenced was that of Norway Spruce, then that of loblolly pine. These suggested that conifer genomes are large (3 to 10 times larger than the human genome), with repetitive sequences. Coast Redwoods are hexaploid, that is, they ave six copies of each chromosome (we are diploid, that is, have only two copies of each chromosome). The DNA of a coast redwood has 27 billion base pairs of DNA, the giant sequoia has 8 billion; by contrast we have circa 3 billion. It is hoped that the Redwood Genome project will see the restoration of areas of coast redwood and giant sequoia that have been lost over the years. The genomic analysis will help inform and guide management strategies, ensuring genetic diversity in the newly planted tree seedlings. Such a strategy will (hopefully) enable newly planted areas to survive and thrive — in the Anthropocene. More on chromosomes Just as it has recently been shown that Coast redwoods are polyploids (i.e. have extra sets of chromosomes), so recent research in the Czech Republic has shown that the common nettle [Urtica dioica] has different ecological ‘preferences’ depending on its chromosomal status. Nettles can be diploid (2n = 26) or tetraploid (2n = 52). The tetraploid nettles seemingly have a broader ecological tolerance and a wide geographical distribution, whilst the diploid nettles occur in a narrower range of ecological conditions. Details of this research can be accessed here (note link opens a PDF) and Plants for a future has lots of information on nettles.
Woodlands web updates. 12.
More problems for bees. There is some evidence that power lines could be affecting honey bees as the lines emit an electro-magnetic field; these fields alter the bees ability to learn. Lab experiments in which bees were exposed to electromagnetic fields similar to those under power lines showed that the bees were slower to learn to respond to a threat More likely to show aggressive behaviour Bee balls and hornets. The asian hornet is an invasive (non-native) species. They arrived in Europe (France) in 2004. DEFRA is trying to prevent them becoming established in the UK through the eradication of individuals and nests. They are honeybee predators, capturing workers and feed them to their young. Back in the ‘home territory’ of the asian hornet, bees have a defence against attack. Hundreds of worker bees quickly swarm into a balls around the hornet. The bees then vibrate their wing muscles so quickly that they generate heat and the temperature inside the ball rises and roast the hornet alive with their body heat. These “hot defensive bee balls” were seen in Japanese honeybees (in 1995). The ball must form quickly before the hornet can send out pheromones to attract others of its kind. Sadly, this act of altruism by the workers comes at a cost. Normally, workers live for several weeks but the bees that contribute to the ball die within 10 days. Unfortunately, our European honeybees do not possess such defensive strategies. Consequently, bee keepers are experimenting with various methods to deter the hornets, for example, meshes, sticky patches and flashing lights on the hives. Warming soils ? Soils store vast amounts of carbon (in the form of humus / organic remains), more than the carbon locked up in trees. Scientists from universities at Exeter and Stockholm have looked at data on some 9000 soil samples from around the world, and found that carbon storage declines with increasing temperature. Coarse soils lose carbon faster than clay rich ones.
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.
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 .
Woodlands Web updates 9
Bark beetles. The blog has reported on bark beetles, and efforts to curtail their spread / damage. Now comes some hopeful news. Scientists have mapped the entire genome of the Eurasian spruce bark beetle. This could pave the way for new avenues of research into bark beetles and better means of pest control. Outbreaks of the beetle can lay waste vast areas of spruce forest, One significant finding is that this beetle has an unusually large number of genes (and therefore enzymes) that help to break down the cell walls of plants. However, whilst it has many genes for breaking down cell wall components, it does not have a similarly high number of genes concerned with the removal of toxins - such as the resin, from the wood it ingests. Now that the genetic make up of the beetle is known, it might be possible to turn off particular genes (using what is termed RNA interference), allowing for a highly specific pest control measure. Researchers at Lund University (Sweden) have identified the special receptors on the antennae of the bark beetle, and the pheromones (ipsenol and ipsienol) that they respond to. It is hoped that this might allow the development of environmentally friendly control measures - through disrupting their pheromone communication. This might be achieved by finding a chemical that binds to the receptors even more strongly than the pheromones. Pollinator decline. The Synthesis Centre for Biodiversity Sciences (Stellenbbosch University) has produced a report about the loss of pollinators and the possible effects on flowering plants. Drawing together the information from hundreds of different published research papers, it is estimated that some 175,000 plant species (roughly half of all flowering plants) rely to a greater or lesser extent on animal pollinators. In fact, a third of flowering plants would be unable to produce seed without pollinators. Since so many wild plants are reliant on pollinators, the decline / loss of pollinators will affect many natural ecosystems. Without pollinators, certain weeds and other plants that do not depend on pollinators may have a greater opportunity to spread - with less competition. Fires. Forest fires have been much in the news in recent years. Wide scale fires have been recorded in the United, States, Sweden, Russia and Australia. Drought is a significant factor as material on the forest / woodland floor dries out and combustible material accumulates. In some areas, the accumulation of combustible material may be associated with changing nomadic practices and declining pastoralism. Pastoralism is based on livestock production [e.g. raising of cattle, sheep, goats, even camels]. Such animals and indeed wild ones graze on vegetation so that combustible material is reduced, and to a degree natural fire breaks form. So, one strategy to mitigate the risk of fire in forests / woodlands is ‘targeted grazing’ by either domesticated animals or indeed wild ones.