Blog - Woodland Web Updates
Woodlands web updates : 27
Tree survival and drought. Researchers at the University of California have been working on a method that helps predict whether forests / woodlands can survive periods of drought. As climate change is altering patterns of snow and rainfall, so periods of drought are likely to become more common. Forests are important in terms of carbon sequestration, that is, they take up carbon dioxide from the air and convert it into sugars, starches etc that are stored in the leaves, branches, stems and roots. However, in order to assimilate and convert carbon dioxide (in photosynthesis), trees (indeed all plants) need a supply of water. When water is limited, trees need to make use of their reserve materials. Just as we make use of body reserves of fat and glycogen when food / diet in inadequate. However, reserves can only sustain a tree for a finite period of time. If drought persists, the tree reaches a ’tipping point’ and it will die. The researchers studied a forest in the Sierra Nevada that experienced a period of drought between 2012 and 2015. During this period, millions of trees died. The team recorded rainfall, soil moisture and temperature in the forest AND the amount of carbon dioxide that the trees absorbed, and their reserve materials. They found that the trees were able to maintain function / health after the onset of the drought but with the passing of time, the trees exhausted their reserves and were unable to use / convert carbon dioxide into food. They had reached the tipping point and died. The methodology of this study was called CARDAMON (carbon data assimilation with a model of carbon assimilation); it is hoped that it can be used to evolve strategies to enhance forest and woodland resilience in the face of climate change. Pollinators. [caption id="attachment_35902" align="aligncenter" width="675"] hoverfly[/caption] University researchers from the UK and Finland have been trying to determine the most effective pollinators of crop plants, like strawberries (and other fruits). Plentiful and effective pollinators are needed to ensure a good harvest of the fruits. The researchers studied the pollinators at three strawberry farms through the (long) growing season for the fruit. They adopted two approaches : They caught the insects that visited the strawberry flowers and analysed the pollen they carried in detail (pollen load and type). They also counted the number of flower visits by the different insects, (a quick way to identify key local pollinators). Many insects were identified, including :- European drone fly : Eristalis arbustorum Honeybee : Apis mellifera Levels drone fly : Eristalis abusivus Buff tailed bumblebee : Bombus terrestris White tailed bumblebee : Bombus lucorum Common drone fly : Eristalis tenax Red tailed bumblebee : Bombus lapidarius Early bumblebee : Bombus pratorum Bent-shinned Morellia : Morellia aenescens Hoverflies are true flies, that is, they belong to the order Diptera or true flies, as they have a pair of wings and a pair of halteres (balancing / orienteering organs used when in flight). Several of the flies in the genus Eristalsis are known as Drone Flies (due to their resemblance to honey bee drones). The larvae of Eristalis species are commonly found in putrid / stagnant water and sometimes referred to as “rat-tailed maggots”. It was noted that pollinators also made use of the wild plants to supplement their diets, as strawberries alone cannot meet the nutritional needs of pollinators. ‘Elsanta’ strawberries have a relatively low sucrose and protein content in both their nectar and pollen. The precise order of importance of pollinators varied between farms. Bee (Apis and Bombus) species and hoverfly (Eristalis) emerged as key pollinators. The European drone fly was the most important pollinator at two of the three farms studied, evidence that hoverflies can be effective pollinators. One farm had commercial hives of the honey bee but they were less significant than the activities of of the hoverflies and bumblebees. The abundance of a particular insect, coupled with its active period were / are important determinants of pollinator importance. Sawdust and plastics - a possible use?. Plastics represent a relatively new, but persistent and major form of pollution (on land, in the sea, indeed everywhere). Whilst many plastic objects are instantly visible in the form of discarded bottles, fast food containers, many plastic pollutants are in the form of very small particles of plastics - nano and microplastics. The concern is that we and other organisms are taking these microscopic particles into our bodies from our food / drinking water. However, it is possible that plant materials may offer some ‘solutions’. Water that contains micro and nano plastics can be filtered through sawdust that has been treated with tannic acid. Tannic acid is large molecule, its molecular formula is C72H52O46 . Tannic Acid is found in certain plant galls (swelling of trees caused by parasitic wasps) and in the twigs of certain trees, such as Chestnut and Oak. The wood sawdust contains fibres of cellulose, combined with hemicelluloses and lignin. Water can flow through this material by capillary action. This plant-based filtration (known as bioCap) of plastic-laden water is capable of dealing with a wide range of nanoplastics (PVC, PET, polyethylene etc), and tests with mice suggest that the filtered water may be sufficiently free of plastic to pose little risk.
woodlands web updates : 26
Trees for a longer life? Researchers from US Forest Service has completed a survey of tree planting in Portland, Oregon and concluded that the more tres are planted in an area, the longer people live. The Portland “Friends of Trees” have planted some 50,000 oaks, dogwoods and other trees around the city over the last thirty years. After adjusting for factors such as race, income, age and education, the team found that where more trees had been been planted, fewer people died. This was true for all areas - wealthy or less so. Furthermore, as the trees aged, the mortality rates of the people nearby went down. Trees generally improve air quality and moderate extreme high temperatures. A recent report in the medical journal The Lancet suggested that many of the premature deaths from the 2015 heat wave in Europe could have been avoided with 30 percent more tree cover. Birds in decline. UK bird populations are in decline. Much of the decline occurred in the 1970’s and 80’s, and was particularly noticeable in populations of farmland and woodland birds. However, the losses have continued in recent times, with a 5% decline between 2015 and 2020. Again, woodland birds have fared poorly with a 12% decline in this period. The steepest decline in population numbers are seen in species such the Tree Sparrow, Willow Tit, Lesser Spotted Woodpecker and Nightingale. These have all declined by 90% or more since the late 1960’s. The Turtle Dove shows the biggest decline of any species. Habitat loss is thought to be the main driver of population decline for many species, but oil and plastic pollution are also factors, as is disease - such as trichomonasis and avian flu Certain species typically associated with urban areas / habitats (Swift, House Martin, Starling and House Sparrow) are also declining. Predation by cats might be a factor, the Mammal Society estimates that cats in the UK catch some 92 million prey items over Spring and Summer, of which around 27 million are birds. Disease such as avian malaria is another factor, one study found 74% of sparrows were infected with the parasite Plasmodium relictum; the changing nature of urban gardens may also be a consideration. Bees and sunflower pollen grains Bees and bumblebees are struggling with various parasites /infections. One parasite is the gut pathogen Crithidia bombi. This is known to affect the ability of bumblebees to create a successful colony. Previous studies have indicated that the the gut microbiome of the bees can help protect against infection by this parasite. Now a study at the University of Massachusetts Amherst has found that sunflower pollen can help bees resist infection. It was not known why sunflower pollen was effective, it could be that the shape of the pollen grains was important or the chemical makeup within the grains, or a combination of the two. To test the ‘anti-parasitic nature of the pollen’, an experiment was set up so that some bees received the outer shell of the sunflower pollen (the sculptured exine), whilst another group received the materials from the centre of the pollen grains (but no outer coverings), and a third group received whole pollen. Bees that received whole pollen grains or just the spiny shells had far less of the parasite in their gut compared to those eating the ‘soft centres’ . The pollen grains and pollen shells reduced infection by 80 to 90+%. So it is the spiny shape of the pollen grains that is important in reducing infection in the bees. 'Physical removal' of pathogens is known in other animals, for example, great apes infected with certain nematodes or tapeworms will consume bristly leaves. These 'irritate' the gut and increase the expulsion of the parasites.
woodlands web updates : 25
Earlier flowering times. A survey has shown that plants are flowering earlier in the year. Cambridge University researchers compared the dates of flowering of some four hundred plus species before and after 1986. They found that plants are now flowering roughly one month earlier. More recent decades have been associated with rising air temperatures. This change in flowering time may have profound consequences for the plants. The vast majority of plants are dependent on pollinating insects (bees, bumblebees, hoverflies) to set seed and complete their life cycles. By flowering early their cycle, plants may not match up with the activities of their pollinators. They may flower but their pollinators bee ‘missing’. Their pollinators need to emerge from their overwintering stage earlier. Earlier flowering may not matter for those plants that are visited by several pollinators but for those that are dependent on one or two specific visitors - it may critical. For example, Sainfoin. Sainfoin is host to a particular (solitary) bee Melitta dimidiata (remote image here). It is a monolectic bee; i.e., a bee that collects food (nectar and pollen) from only one species of flower - the sainfoin. If the sainfoin flowers earlier in the year and the bee does not match the shift in flowering, then the bee has a problem. Work on the effects of climate change on pollinators has been somewhat limited to date, but studies in Japan suggest that bees / bumblebees are somewhat behind plants in their response to environmental changes. Bee and bumblebee news. Recent research data provide evidence that (buff tailed) bumblebees are not able to detect or avoid concentrations of pesticides [imidacloprid, thiamethoxam, clothianidin, or sulfoxaflor], as used ‘on the farm’ - from signals sent by their mouthparts. The mouthparts are covered with tiny hairs and these hairs have ‘pores’ in them. Chemicals pass through these ‘pores’ to sensory cells; this is how the bee tastes and smells. It seems likely that the bumblebees are at considerable risk of consuming pesticides in their search for nectar when visiting pesticide-treated crops. [caption id="attachment_19675" align="alignleft" width="300"] Bumbles foraging in artichoke[/caption] Another agrochemical, Roundup, has been found to affect the learning and memory of bumblebees. Roundup, which contains glyphosate, affects their ability to learn and memorise connections between colour and taste. Impaired colour vision is likely to affect the foraging and nesting success of the bees. The research was conducted in Finland by researchers at the University of Turku. In yet another concerning study, researchers at the University of Maryland have found that the life span of laboratory-raised honey bees has reduced considerably. Five decades ago, the lifespan for a worker honeybee (Apis mellifera) under controlled laboratory conditions was about 34 days. Now it is some 17/ 18 days - according the report in Nature. The study also reviewed the scientific literature [from the 1970s to now] and noted a trend in the life span of bees. Shortened worker bee lifespan has implications for colony health and survivorship. The work at the University of Maryland is ongoing. Methane release. Ghost forests are found in coastal areas. As a consequence of climate change, sea water has ‘invaded’ low laying areas and trees have died. The dead trees are sometimes referred to as ‘snags. A number of woodland / forest communities along the eastern coast of the United States have been affected. Recent work by North Carolina State University has shown that these ghost forests release methane. The methane is generated by bacteria in the soil but then ‘escapes’ by means of the ‘snags’. As it passes through the wood of the ‘snags’, microbes may consume and alter the methane. As methane is a potent greenhouse gas, understanding the nature and extent of these methane emissions from ‘ghost forests’ is important. Tree rings The study of tree rings has been invaluable in dating many historic objects ./ archaeological sites. Now, it seems that they could play a role in estimating the amount of carbon that trees are actually absorbing (carbon sequestration), if woodland / forest inventories are coupled with core samples of the trees. The measurement of the annual rings from such cores could create a record of ‘tree growth across space and time’, yielding a more accurate estimate of the amount of carbon being taken up by woodland and forests. Forests, soils and oceans are major ‘carbon sinks’.
woodland web updates : 24
Electric bees ? Both bumblebees and flowers carry an electric charge. Flowers have a weak negative charge, whilst the bees have a positive charge. The attraction between these two opposing electric fields may help the bees sense flowers. The electric charge of a bee may even stimulate a flower to release a burst of scent, aka volatile organic compounds. This was true for petunias, but not snapdragons. When a bee has visited a flower, the negative charge is briefly lost - maybe a signal to tell other bbees not to visit? Other work by Bristol University has indicated that synthetic fertilisers and pesticide can interfere with a flower’s electric charge for some time after spraying, and that this can modify the foraging of bumblebees. "Black bees" The black bee, Apis mellifera mellifera, faces a number of threats like the domestic honey bee. It is also known as the European Dark Bee or the Black German Bee. It has been present since the retreat of the last Ice Age, but its distribution has become restricted as a result of habitat loss, parasitism by Varroa mites and viruses. The black bee can be distinguished from other honey bees by its stocky body and sparse abdominal hair (which is brown), and overall dark coloration - so they appear black or dark brown. Recent research (using DNA analysis) has shown that black honeybees can be found in many locations in Ireland and are not extinct, as previously suggested Black bees are noted for their longevity and hardiness (ability to cope with winter temperatures); it is possible that if winters become shorter / milder that this change may not favour black bees. Weird weeds? It seems that our gardens may be home to ‘new’ or unusual species of plants. The Royal Horticultural Society would like gardeners to report on interesting ‘weeds’ that might find as they could be rare plants or plants growing in unusual places / areas. You are asked to take photographs of anything that you find interesting, and upload the images to iNaturalist. Reporting on unusual plants is not the only thing that the RHS is interested in. There are other garden projects that one can contribute to, for example, reporting sightings of garden pests such as the berberis sawfly, cellar slug, hemerocallis gall midge, lily beetle, rosemary beetle and spittlebug. Mycorrhizal networks. A common mycorrhizal network (CMN) is when fungal hyphae connect the roots of many plants (either of the same or different species) below ground. They have attracted considerable attention in recent times (woodland wide webs), with claims, for example, that resources are transferred through CMNs to increase seedling performance and mature trees send resources / defence signals to offspring etc. However, a recent report in Nature has suggested that there is a ‘bias’ towards citing the positive effects of CMNs and that, to date, knowledge of common mycorrhizal networks is limited.
Woodland web updates : 23
No match for nonpareil ? Many varieties of apples have been around for centuries. For example, the nonpareil which was bred (in France) back in 1696, the Egremonet russet much admired for its flavour and appearance dates from Victorian times. The Cox's Orange Pippin is a cultivar first grown at Colnbrook in Buckinghamshire by Richard Cox. By end the of the C19th, the Cox’s pippin was one of the most popular apples. However, there is a concern for these heritage apples in our changing climate. In recent years, we have experienced warmer and wetter winters. Such winters do not offer enough chilling hours for these trees. Many trees need a period of cold in the winter months, where the temperatures are below 6oC but above freezing. About 1000 chilling hours are needed for apples such as the nonpareil. However, winters are present are offering approximately 600 chilling hours. Gala apple trees (developed in New Zealand) need only 600 chilling hours but it might be that they will not respond well to the wet winters we (currently) experience. Some feel that they do not offer the complex flavours of ‘classic apples’. Kew Gardens has now planted a varied selection of apple trees One third are heritage apple trees One third are ‘new’ varieties needing fewer chilling hours One third are varieties from countries warmer than the UK Over the coming years, the trees will be monitored to see which ‘do best’ in terms of cropping in London’s warming temperatures. The apple-growing industry in the UK is under considerable strain, with many growers unable to afford replanting this year. Growers ‘refresh’ their orchards regularly, replacing older trees with new ones, but now many cannot afford to do this. The sector is struggling with a shortage of workers - made worse since the UK's exit from the European Union high energy costs low returns from the supermarkets that buy their produce The option to ‘buy British’ may become a much rarer option. Further details here Recovery after forest fires. Bacteria and fungi are the first to start rebuilding from the charred remains of burnt forest and woodland. The number and variety of microbes falls dramatically after a fire. Then, there was a microbial succession in the burned soil, that is, the number and types of bacteria and fungi changed quite quickly, with fast growing types able to advantage of the reduced competition for resources. The situation is not dissimilar to what happens to our gut microbiome when we have to take antibiotics. Antibiotics ‘knock out’ many of the useful bacteria in our gut, but gradually the microbiome is re-established. Reporting on weeds. It seems that our gardens may be home to ‘new’ or unusual species of plants. The Royal Horticultural Society would like gardeners to report on interesting ‘weeds’ that might find as they could be rare plants or plants growing in unusual places / areas. You are asked to take photographs of anything that you find interesting and upload the images to iNaturalist. Reporting on unusual plants is not the only thing that the RHS is interested in. There are other garden projects that one can contribute to, for example, reporting sightings of garden pests such as the berberis sawfly, cellar slug, hemerocallis gall midge, lily beetle, rosemary beetle and spittlebug.
woodlands web update – 22
Back to one’s roots? Some of the effects of agriculture are very obvious, such as the vast areas of land now covered by monocultures of wheat or oil seed rape. The expansion of mechanised agriculture has resulted in significant reductions in biodiversity, for example, through the loss of hedgerows and ponds (see the post on ghost ponds in Norfolk). However, agriculture has others effects that are not quite so obvious. Soils are ‘filled’ with roots, and roots help engineer landscapes. They help: break up bedrock, improve permeability of the soil to water stabilise the soil, store carbon transport water and minerals to the plants. They have been doing this for millions of years since the colonisation of land by plants. Now, research by scientists in the United States, has shown that the roots of agricultural crops are significantly less deep than those of the natural vegetation in an area. Indeed, the root depth may be shallower by some 60 cm, compared to the natural root systems of an area. If the soil is less root material then there is decreased carbon storage, reduced nutrient recycling and possibly reduced soil stability. Whilst there are some areas where “woody encroachment” is occurring (for example, shrubland taking over in some grasslands and forest advance into regions of tundra so root depth is increasing) - the onward march of agriculture is dominant. Full details of this analysis / research : https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022EF002897 Shrinking in winter Recent research has shown that some small mammals (like moles and shrews) shrink in size during periods of cold temperature. This shrinking is thought to be a response to cold temperature rather than lack of resources. This change in form has been known for some 70 years and is referred to as Dehnel’s phenomenon. Professor Dehnel observed this change in form in shrews [in Poland in 1949]. However, shrews have a short lifespan so an extended studied of this phenomenon with these animals was not / is not possible. Recent studies by German researchers have focused on moles, who can survive harsh winters by becoming smaller. It is thought that this reduction in size enables energy savings. According to Dr Dina Dechmann this reduction in size comes at a cost, as the animals’ cognitive behaviour is affected. Further information here : https://royalsocietypublishing.org/doi/10.1098/rsos.220652 Farming and sustainability With the expansion of farming, less and less of the land is available for our native plants and animals, Hedgerows and ponds have been lost / removed, natural habitats have been reduced. The government has produced new guidance on environmental land management schemes (ELMs). That is subsidies that will be paid to farmers if they help promote and protect nature and improve the environment (e.g. using less insecticide and reducing pollution). There would be payment /subsidies for some 280 measures, for example : Creating fenland from lowland peat Maintaining sphagnum moss Creating land that could produce organic fruit Establishing a skylark plot Adding organic matter to the soil Creating green cover over winter (on 70% of the land) Welcome as these measures might be, there is criticism that they favour big arable farmers and do not really help those working on more marginal land (such as upland and moorland regions). Further information available here. Trees - From Root to Leaf For those who like their trees, here is a new book about them. Written by Paul Smith -who was head of the Millennium Seed Bank of the Royal Botanic Garden, Kew. Not read or seen a copy but the Sunday Times comment "'Stunningly illustrated and detailed ... a celebration of all things arboreal, from the seeds, leaves, flowers and fruit to the diversity of trees and how they have influenced art, culture and science' suggests that it might interest. See "https://press.uchicago.edu/ucp/books/book/chicago/T/bo186012850.html"
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.