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Woodland web updates 14.

Woodland web updates 14.

by The blog at woodlands.co.uk, 3 February, 2022, 0 comments

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

Woodlands web updates : 13

by The blog at woodlands.co.uk, 2 February, 2022, 0 comments

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.    
bee

Woodlands web updates. 12.

by The blog at woodlands.co.uk, 27 December, 2021, 0 comments

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

Woodlands web updates 11

by The blog at woodlands.co.uk, 5 December, 2021, 0 comments

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.

woodlands web updates 10.

by The blog at woodlands.co.uk, 11 November, 2021, 2 comments

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

Woodlands Web updates 9

by The blog at woodlands.co.uk, 31 October, 2021, 2 comments

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.
Woodland web updates- 8.

Woodland web updates- 8.

by The blog at woodlands.co.uk, 15 October, 2021, 0 comments

Migrating hoverflies. Hoverflies are important pollinators, plus they also act as important predators  of crop pests such as Aphids.  Some hoverflies (like the pied and yellow clubbed hoverflies) spend the summer in the U.K. but then fly to the Mediterranean or North Africa come the autumn. They begin these migrations on sunny days but simply flying towards the sun would take them on a rather long winded  route.  A study by a research team at Exeter University suggests that they are able to account for the sun’s movement using their circadian rhythm - an internal clock.   If the circadian rhythm of the hoverfly is disrupted, then so is its flight path. Migrating cuckoos. Like many other birds, cuckoos are in decline.  Some time back, the BTO set up a research unit to learn more about the  decline and behaviour of cuckoos.  The work of this group has revealed details of the cuckoos’ migration routes and its winter homelands. Cuckoos have two routes out of the UK : They migrate out south west via Spain and Morocco - the WEST route, or  They take a south east route via Italy and the Balkans (the EAST route) but Both routes ultimately converge on the Congo Basin in Central Africa. However, the birds that take the WEST route leave some eight days later than those taken the EAST route, but were more likely to die en route. Most of the mortality of the birds occurs in the European section of the migration path.  This may be a reflection of the status of their stop-over sites.  Problems might include : Habitat change, droughts and wildfires Decline in food sources (e.g. large moth caterpillars). A lot more detail / information on this project can be found here. VOC’s The air around us is a mixture of different gases / particles / and aerosols.  An aerosol is itself a ‘mixture’ of very small particles (solid or liquid) in air.  These particles can come from a variety of sources :such as volcanoes, cars, trucks and wood fires. Examples of aerosols include  mist,  cigarette smoke,  fires volcanoes car exhaust fumes.   Some trees and plants also release volatile organic compounds (VOCs), for example  Pine trees release alpha-pinene.  Recent research has established that these volatile compounds / vapours are not only responsible for the characteristic scent, but are also important in the formation of aerosols found in the air in and around such woodlands and forests.   Atmospheric aerosols scatter and absorb light, and also influence the formation of clouds, though these processes are not fully understood.  Recent research by the University of East Finland has showed that biogenic aerosols (formed from VOCs) can reduce the amount of solar radiation that reaches the earth’ surface.  They help scatter the radiation back into space.  These biogenic aerosols increase the number of cloud droplets and make the clouds more reflective.
Woodlands web updates 7

Woodlands web updates 7

by The blog at woodlands.co.uk, 2 October, 2021, 0 comments

The British Dragonfly Society has produced a report “State of Dragonflies, 2021”.  Dragonflies display the usual characteristics of insects, three pairs of jointed legs, three clear divisions to the body, compound eyes and a pair of antennae.  They also have two  pairs of (transparent) wings.  The hindwings are broader than the forewings so they belong to the group - Anisoptera (from the greek unequal wings).  They can fly fast and manoeuvre well.  Their ancestors were some of the first winged insects to evolve. The report notes that Many species have increased their distribution (since 1970), for example, the emperor dragonfly,  the ruddy darter. Though some like the black darter seem to be in decline; this may be associated with a lack of heathland management and the drying of blanket bog areas. Several species have arrived in Britain from Southern Europe for the first time, with others returning after long absences.  The vagrant emperor is a long distance migrant from Africa and the Middle East. It is thought that it might now be breeding more regularly in Southern Europe so that some now migrate northwards more often. Dragonflies are moving northwards across Britain and Ireland (associated with warming temperatures and climate change) Whilst the distribution of species has increased, the actual numbers of different species is not known so it is not possible to say if dragonfly numbers have increased overall. However, compared to many reports on the collapse of insect numbers, it would seem that that many dragonfly species are responding to climate warming and an increase in the number of ponds (for example, see the woodlands blog of the restoration of ghost ponds in Norfolk), lakes, gravel pits in recent years. The larval stages of dragonflies (nymphs) are spent in water. Apart from changing the distribution of various animals (and plants), climate change can have other effects.  Some homeotherms ‘warm blooded’ animals (birds and mammals) are undergoing changes in their body form or ‘shape shifting’.  Sara Ryder et al of Deakin University, Australia has studied several species of Australian parrot and has found that their beak size has increased since the nineteenth century:  this increase in beak size is thought to be associated with better heat exchange.  Other research has reported on changes to tail length in wood mice, also tail and leg size in masked shrews.  The changes are generally less than 10% but they do seem to be responses to changing climatic conditions. Pampas grass (Cortaderia selloana) is a tall, clump forming grass with attractive plumes that can find a home at the coast, in town or in your garden.  It was originally a species native to South America. However, it now has a much wider distribution, mainly due to its use as an ornamental plant though it was also used in South Africa to control erosion on dumps around mines. Each plume can produce tens of thousands of seeds.  Consequently, it is now regarded as an invasive species in many countries. It has expanded across industrial and urban areas, squeezing out native species in coastal regions of France, Spain and Portugal, Now the IUCN (International Union for the Conservation of Nature) has introduced a system to recognise the threats posed by harmful species (such as Pampas Grass)  - The Environmental Impacts Classification of Alien Taxa.

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