Blog - Flora & Fauna
Woodland web updates- 8 : migrants and aerosols.
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.
Woodland and forest cover
Compared to some of our European neighbours, it seems that our percentage woodland and forest cover is quite low at 13%; as was recently discussed on the BBC "More or less" programme. Only Denmark and the Netherlands have similar low levels of cover. Finland, on the other hand, has almost three quarters of its surface area covered with trees. After the end of the last ice age, trees gradually recolonised the exposed landscape so that vast swathes of the U.K. were covered with woodland/forest - the wildwood. It might be thought that our current low figure is due to increased urbanisation, road/motorway construction etc. In fact, the tree cover is remarkably similar to that at the end of the first millennium CE. More trees were ‘lost’ in succeeding centuries with the expansion of farming, and trees were harvested for boat building and house construction. The Mary Rose was built using oak and elm. It was the first big ship of the Tudor naval fleet. It has been estimated that over 600 trees were needed for its construction; that is equivalent to about 16 hectares of forest/woodland. Wood was also used to produce charcoal, which was used to smelt metals, particularly iron. The history of charcoal burners in the New Forest is well documented. Many woodlands / forests were the preserve of the landed gentry and the aristocracy and reserved for deer hunting. Anyone caught killing deer or boar from such woodlands could suffer terrible punishments but would more likely be fined.. Woodland and forest continued to be depleted so that by the end of the seventeenth century, the percentage cover had fallen to 8%. At the beginning of the twentieth century, the figure stood at a pitiful 5.2%. The Asquith administration in 1916 established a committee to report on the country’s woodlands and timber supplies. This lead to the setting up of the Forestry Commission which was not just concerned with established ‘strategic reserves of timber’ but also trying to create viable communities in marginal areas. Through its efforts over the succeeding decades, the U.K’s area of woodland and forest has increased significantly - though the Forestry Commission’s heavy use of coniferous species (particularly in the 60’s and 70’s) has been criticised. Coniferous woodland / plantations do not support such a wide range of plant and animal life as deciduous woodland. However, their current emphasis on diversity (and recreational use) favours a much wider range of species, including broadleaved/deciduous trees and the development of a richer ground flora.
What are Buckingham Palace Gardens like from the inside? And what are the Royal gardeners trying to achieve?
The main thing about the queen's gardens is that they are very private. They are large (39 acres) and surrounded by busy roads but not many people get a chance to go inside and even fewer get the inside story from the horse's mouth. So my guided tour around the gardens this week with the Head Gardener, Mark Lane, was an unusual insight, made possible by being a member of the Royal Forestry Society. Mark explained that the Queen wanted no photos whatsoever of the garden and he wouldn't even let me take a mugshot of him. Beyond the privacy that exists within the garden, there are extensive efforts to keep it hidden from the outside - the eight gardeners and dozens of contractors have planted evergreen trees and shrubs just inside the walls to shield the gardens from voyeurs in neighbouring high-rise buildings. And there's a lot to hide with a 3.5 acre lake, a tennis court, statues, a summer-house with its very own corgi (stuffed, I think), and a private borehole for watering and lake-filling. Mark Lane has been working in the garden for over 40 years, 30 of those as Head Gardener so the planting and design are very much a joint creation by him and the Queen herself, working to create a giant secret garden on what is, in essence, a triangular traffic island. They have tried to plant as many different species as possible so you are also in what could be thought of as an arboretum - I saw no weeds whatsoever so it's probably fair to say that there is not a tight budgetary constraint. Mark's bold claim is that "any habitat you can name we have an example of here." I walked along the herbaceous border for 150 metres without seeing the same plant twice, apart from the six or seven banana plants. This border runs along the edge of a lawn extensive enough for a helicopter to land. Indeed one chopper touched down just before the coronation in 1953 making it London's oldest helipad, now reinforced with matting underneath the lawn. Behind this is the lake with two islands, both rarely visited by Royals - or other humans - to encourage wildlife there. Another semi-secret element is the woodland path behind the herbaceous border for the Queen to use on occasions "when she wants some peace and quiet". Apart from creating a pleasure garden for the Royal family, the gardeners are focused on the three big garden parties the Queen holds in early summer each year (aside from Covid years). Each one is for 7,500 guests, who are allowed to roam freely around the gardens. Mark and his team are so concentrated on these events that his motto for each party day is, "not a leaf out of place". They also prune the roses in late autumn rather than Spring so that they bloom and are at their best for the parties. His main criteria for choosing the species of rose are that they should have maximum fragrance and be disease resistant. "Every garden," insists Mark, "should have a conservation plan" and Buckingham Palace Gardens has one: they recycle 99% of their waste, they have bee hives on the island, they retain rotting Robinia trees for the bats, and they have much increased their areas of meadow grasses. These grassy patches have been good for moths and butterflies and the gardeners can be sure of this because every year they choose several nights to set up overnight moth traps. Using a mercury light, they trap, count and then release dozens of species and they have a record of this annual audit going back to 1956. Other species are not so lucky - grey squirrels are "controlled" though Mark was too coy, even with the group of foresters I was accompanying, to say whether he shoots, traps or poisons these "tree rats" It seems that being Royal doesn't stop your trees or garden from suffering from pests and diseases. Honey fungus is a menace that they attack using fungicides and "air-spading", whilst Oak Processionary Moth nests are removed for incineration, and even their London Plane trees are attacked by the Massaria fungus which has been present in London since 2007. Buckingham Palace Gardens have a very long history and at one time had a four-acre mulberry garden to produce silk worms. The King at the time (King James 1st) was so keen on silk production that he ordered every county in the country to plant 1,000 Mulberry Trees, some of which still survive such as the ones at Charlton House in South East London. The variety and quality of trees mean that Buckingham Palace Gardens has 15 National Champion trees, three of which were planted by the Royal family. One of the most unusual plants we stumbled across was the Ilex vomitaria, a species of holly which, when eaten, makes the consumer vomit. But my favourite was the common hawthorn whose berries had been recently harvested - they are used to make Buckingham Palace Gin which for £30 a bottle is available commercially (who said the Queen doesn't share?!). All the hundreds of varieties of trees and shrubs are part of Mark Lane's aspiration as Head Gardener which he describes as "to create a garden that is notable not just because it's attached to Buckingham Palace but which stands on its own merit." He told us of an incident in the gardens, when the queen was meeting a man who was one of thousands of guests at one of the tea parties. His phone went off and he looked a bit confused, not sure whether to take the call. She advised encouragingly, "yes, take it - it might be someone important." Although photos are not allowed it seems some have been smuggled out. If you search "Buckingham Palace gardens" on Google images you'll find a nice collection of snaps. My pictures are all from outside, trying to look in. Have you visited? What was your impression?
Big Butterfly count 2021.
Butterfly Conservation has organised the Big Butterfly Count for the last twelve years. This year, the count took place between 16th July and August 8th. The count gives some information of how butterfly and moth populations are faring. Both butterfly and moth numbers give us some information about the ‘health’ of our environment, and indeed what has been termed the insect apocalypse. Though some 150,000 counts were registered this year, the ‘average’ number of butterflies / moths recorded per count was nine. This was down from the average count of 11 last year, and 16 in 2019. The total number of butterflies / moths counted was down by some 14% overall compared to last year. Those species that had significantly reduced counts were Peacock down by 64% Common Blue down by 59% Speckled wood was down by 41% Small tortoiseshell and the Comma dropped by 32% On a more positive note, the ringlet and marbled white were recorded in greater numbers (but they did have low counts last year). The Spring weather was probably a significant factor in these generally disappointing results. The wet May would not have helped breeding or feeding; low temperatures are not conducive to activity. The poor weather would particularly impact on those species that normally produce two broads a year. Further information on the results of the count can be found the Butterfly Conservation website : here.
Viruses, Varroa and honey bees.
Honey bees are often infected by the mite - Varroa. Mites are small arachnids. The varroa mite is an external parasite, attaching to the body of the bee and feeding from it. It also infects honey bees with various viruses, which further harm the bees. One such virus is the deformed wing virus. Bees that are severely infected with this virus die within days, some have such poorly developed wings that they cannot properly forage for nectar and pollen. The virus also affects their ability to learn, so that if they forage they may not be able to find their way ‘home’. Lost bees die, the colony is deprived of food collected by such bees and the colony may collapse. Eliminating the mite is difficult and the use of chemicals risks contaminating any honey collected from treated colonies / hives. However, researchers at the National Taiwan University have found a naturally occurring compound that may help alleviate the effects of the virus. The compound in question is sodium butyrate Na(C3H7COO). In a series of experiments, the research team found that bees that were fed sugar-water laced with butyrate were better able to resist the effects of subsequent viral infection. Compared to a control group that did not have butyrate, some 90% were still alive five days after infection whereas 90% of the control group died. The butyrate treatment also improved the bees’ ability to forage and return to the hive. Further details of this work here. Sodium butyrate is an inexpensive chemical, and if its benefits are substantiated then it could provide an affordable solution to the mite and virus problem that honey bees face.
opening and closing – flowers, leaves …..
Some flowers are open during the day, ready to receive visitors (pollinators) but close up each night at dusk; for example, crocuses, tulips, poppies. Other plants move their leaves in response to light and dark. Such movements of flowers and leaves are known as nyctinastic movements. The reasons for these movements are not particularly clear / obvious. A number of suggestions have been advanced : The closing of the petals at night might serve to keep pollen dry. When wetted, pollen is heavier and less easy for insects to distribute. By closing at night, the nectar and pollen is protected from unwanted visitors. Some insects are nectar robbers that is they take nectar but do not contribute to pollination. Darwin made the suggestion that the closing might help protect the floral organs from the chill of night time temperature. Leaves may move to help capture rain, closing down at night to allow water to trickle down to the roots (?). Different explanations may apply to different plants but these movements have a common underlying mechanism, namely phytochrome. Phytochrome is a blue-green light absorbing pigment. It responds to red (in the region of 660 nM) and far red light (>730 nM). Red light is generally abundant during the day, but the balance between red and far red shifts towards the end of the day. This change is detected by phytochrome and it directs the plant’s circadian / daily rhythm. Phytochrome is involved in many processes during a plant’s life cycle from germination to flowering. The nyctinastic movements of plant parts is, however, largely controlled by the movement of water into and out of cells - cells can swell or shrink. Some plants have special structures called pulvini to control the movement of leaves. Pulvini are found in the bean family (Fabaceae), and plants like the sensitive plant (Mimosa pudica) and the Prayer plant (Maranta sp). Pulvini are usually located on the leaf stalk (petiole). A pulvinus is a small swelling on the stalk, it has a central core of vascular (water-conducting) tissue surrounded thin-walled cells (parenchyma tissue) with large fluid-filled vacuoles. The flow of water in and out of the vacuoles of these cells raises or lowers the leaf stalk / leaf. [caption id="attachment_36023" align="aligncenter" width="650"] Pulvinus on sensitive plant[/caption] [caption id="attachment_36032" align="aligncenter" width="650"] Young Mimosa pudica[/caption]
Oak trees, moths and resilience.
Ecology is concerned with understanding the relationships between organisms, and their relationship with their environment. This can involve how climate and soil influence the growth and development of organisms. Ecological studies may focus on a particular organism (autecology) or specific areas. One area that has been intensely studied is Wytham Wood, which lies just outside Oxford. The area includes ancient semi-natural woodland, secondary woodland, grassland and ponds. It is a designated SSSI, where some 500+ plant species and 800+ lepidopteran (butterfly and moth) species have been recorded. Records of bird populations go back some sixty or more years (with the work of David Lack and others); other ecological studies with long-term data include those on badgers, and also work on climate change. Wytham Wood belongs to Oxford University. Historically speaking, it is possibly the most intensely studied woodland in the world. Read more...
Woodland web updates 6.
Pesticides problems. The effect of pesticides on bees and bumble bees is now well documented. However, the combined effect of different pesticides is less well known. If pesticide A is known to kill 10% of the bees in an area that has been treated, and pesticide B kills another 10% then it might be reasonable to assume that 20% of the bees would be killed - IF the effects are additive. However, evidence is beginning to indicate that the effects of the pesticides is more than the sum of the parts - the pesticides work together / synergistically. Pesticide formulations that are sold to farmers are often ready mixed ‘cocktails’ so exposure to more than one pesticide is often the norm, so it is important that these co-operative effects are understood and known. Honey bees have been affected by not only pesticides but also varroa. Varroa is a mite, which lives and feeds on honeybees and their larvae. Fortunately, bees have complex hygienic behaviours, for example, removing dead larvae or pupae. Research indicates that honey bees are modifying this behaviour to deal with varroa mites. Helping pollinators Researchers at the University of Freiburg have recently published work establishing the importance of semi-natural habitat regions next to orchards and other agricultural landscapes for pollinators. Such areas (ditches, banks, overgrown fences etc) help ensure that flowers (and therefore nectar and pollen) are available over a significant period of time. This is important for pollinators such as hover flies, solitary bees, bumblebees etc. as nectar / pollen provided by crops is only available for a short and limited period. Such areas are also important for overwintering, nesting sites, providing food for larval stages etc). Their work focused on orchards near Lake Constance in Southern Germany. Soil remediation with lupins. There are many sites around the world where the soil is contaminated with metals (such as arsenic) as a result of past mining / industrial activities. Such arsenic contaminated soil might be ‘revived’ by using the natural mechanisms that some plants have evolved to deal with certain contaminants. The white lupin (Lupinus alba) is an arsenic-tolerant plant that might be a candidate for phytoremediation of soil. The tolerance of the white lupin to arsenic is thought to be due to the release of chemicals by the roots into the soil. Staff at the University de Montréal placed nylon pouches close to the roots to capture the molecule released. The chemicals were then analysed to see which could bind to the arsenic (phytochelatins). Phytochelatins are known to be used within plants to deal with metals but here they seem to be used externally. Quite how they work is yet to be determined.