The soil in many arid ecosystems (for example, savanna, deserts, & shrublands) is often covered by a thin layer of organisms, a community of lichens, mosses, liverworts, fungi, cyanobacteria and other microbes. They form a biocrust in the very top layer of the soil.  These organisms produce a variety of chemicals that glues together the soil particles.  Most biocrusts start of with a single type of organism (often a lichen or cyanobacteria, they are hardy). As these grow, they change the immediate environment so that others can then colonise the area so slowly the community grows.. The resulting biocrusts are important in helping reducing soil erosion and dust production.  Whilst dust can hold nutrients that will benefit plants as and when it is deposited, it can also have negative effects. Dust reduces water and air quality.  Dust storms can be truly massive and terrifying, for example, the 2009 Australian Dust storm. Occasionally, in this country we experience saharan dust that his been carried hundreds of miles on the wind.  If wind-blown dust lands on glaciers, snow or ice sheets then it affects the albedo.  The albedo is a measure of a surface’s ability to absorb and retain energy, or putting it the other way round, the ability to reflect heat / light energy.  Dark coloured objects tend to absorb more light energy than light coloured surfaces.  So if snow or ice becomes coated with dust, it will absorb more heat and may melt.   Biocrusts prevent many millions of tonnes of dusts entering the atmosphere each year.  It is thought that they may cover some 12% of the earth’s land surface.  Soil with a biocrust needs a far stronger wind before it starts to erode.  Sadly, like many other things, biocrusts are under threat due to climate change and shifting patterns of land use. [caption id="attachment_41261" align="aligncenter" width="675"] Church wall being colonised by Lichens[/caption] Biocrusts can also form on walls and buildings, for example, lichens and mosses colonise gravestones.  Whilst biocrusts have positive effects when they form on soils, it is thought that they can have deleterious effects on stone / brick surfaces due to the various organic acids and other chemicals that the colonising organisms can produce.  The production of these chemicals can degrade (weather) structures and lose their integrity / aesthetic appeal.   The Great Wall of China, which once stretched for some 8000+ kilometres, is protected by biocrusts in parts.  Construction of the wall started about. 200 BCE and continued (on and off) till the 1600’s CE.  Much of the wall has now been lost.  Some parts of the wall were made from stone and bricks (held together by sticky rice mortar). Other sections were constructed from ‘rammed earth’, made by compressing natural materials (eg. chalk, gravel, lime) with soil.  Some have regarded these sections of the wall as ‘weak points’.  Recent work by Bo Xiang and colleagues found that the ‘rammed earth’ sections were often covered by a biocrust, (of lichens, mosses and cyanobacteria).  This biocrust actually helps maintain the integrity of the wall by protecting it from wind and water erosion.  It reduces temperature extremes and the porosity of the wall, reducing infiltration and its water holding capacity.  All of these help maintain the integrity of these sections of the wall. If biocrusts are lost, through fire, climate change or human intervention then recovery can be problematic.  Organisms like cyanobacteria may recolonise a site quite quickly by organisms blowing in from nearby and undisturbed areas.  Full recovery of the crust and composition generally occurs more rapidly where the soil is fine  textured and moist. When the soil is coarse and dry then re-establishment of a biocrust may take hundreds or thousands of years. Thanks to Art for lichen image on church wall.  

Big Bertha, Darth Vader, and Inchy are just some of the names people use for their chainsaws, mauls, and winches. Others, of course, only ever use the correct name for their forestry equipment, but they are missing out on the advantages of nicknaming. Apart from entertainment and exercising a dry sense of humor, there are some good reasons for naming your forestry kit. By using personalized names, you can agree on the right tool for the job. In the case of one forester with two hydraulic jacks, he called the larger one Jack and the smaller one Jill. It’s useful to distinguish like this if you are asking someone to bring a particular tool from the car or van. Another benefit of naming is to remind yourself of the dangers of certain tools. Hammers are sometimes called finger finders, and those heavy post knockers are sometimes called “Clonkers” because of their tendency to clonk the user on the head. Some tool nicknames are just more intuitive than the more formal names, with some woodworkers calling a spirit level a “bubble stick.” One forester calls the wedge used in felling her “Cheesey.” Others are just short names and therefore easier to say, such as “Thor” rather than sledgehammer, smashing three syllables into one. Most foresters enjoy a bit of quirkiness, and names sometimes refer to where the tool was acquired (“my auction saw”) or something about its history. One bandsaw user had a blue safety switch on his saw, but when he replaced it, the same button was green, so he forever referred to it as the “green blue button.” Perhaps we name our forestry tools because they become our trusted friends, and we want to show affection and respect, or maybe it's for practical reasons. Do you name yours?

‘Trees for Life’ and ‘Woodland Trust Scotland’ are trying to revive lost pinewoods, that once formed part of the Caledonian Forest.  This forest supported a rich and diverse flora and fauna, including serrated wintergreen, distinctive lichens, crossbills, capercaillie, wild cats and red squirrels.   After the last Ice Age, plant and animal species moved across the 'land bridge' that connected us with continental Europe.   Pines (Scots Pine aka Pinus sylvestris) were ‘quick’ to move into Scotland and the land vacated by the glaciers.  Now less than 2% of this once great forest survives. To find pockets of ancient and ‘lost’ pine trees, these two organisations have adopted a number of approaches. Making use of old maps and texts, for example, those produced by the Reverend Timothy Pont (a Scottish minister and cartographer) in the 1500s. He was the first to produce a detailed map of Scotland.  These can point to areas that were formerly populated by “fir trees”, ie pine. Examining Gaelic place names, which might reference woodland or pine trees. Using the original ordnance survey maps (which often had fir tree symbols) to produce digital copies, which can be overlain on modern maps - hopefully to reveal former woodland sites. Using ecological evidence.  For example, wild pine often grows with old birch trees, whereas planted pine is usually found with larch and other ‘commercial conifers’. Old pine trees often have a distorted shape, with thick, gnarled and twisted trunks; they survive in remote gorges and crags.  Areas that previously supported wild pine, often have old stumps still present and / or certain distinctive lichens / plants - remnants of once diverse ecosystem. Using these various techniques, dozens of lost pine woodland areas have been identified and located.  Much of the original Caledonian Forest was lost through felling (for timber and / or fuel) over the centuries.   Later came sheep farming and this was followed in Victorian times by deer and grouse shooting.  In the last century, commercial forestry resulted in the further loss of ancient woodland. However, restoration is possible.  Where some old trees have survived, there is often a seed bank in the soil and these seeds can germinate if the dense canopy of commercial conifers is removed.  Many pine seeds that do germinate are lost as seedlings due to grazing due to deer or sheep - who seem to prefer them to Sitka etc.  Hopefully as areas with pine grow on, so other species such as rowan, birch and hazel will develop and in time a ‘full’ woodland will develop.

Last week's woodlands’ blog talked about the fall in insect numbers across the UK.  This is not just a UK problem, it is far more widespread.  Insects,  bees and bumblebees as pollinators aside,  are important in ecosystems;  there are armies of other insects that are providing ‘services’ for us. When a tree dies in a woodland, bacteria and fungi are important agents in the decay of the tree and the recycling of elements, but they are assisted by beetles. If the dead tree was a veteran, during its lifetime it will have provided  a variety of micro-habitats.  Holes and crevices would have been used by bats,  birds,  insects etc.  Now, the the decaying wood will be support different organisms, from microbes to larger fungi, such as bracket fungi that can erupt from surface of the dead tree.   As the wood decays,  the material may become a ‘home’ for saproxylic beetles. For example, Stag beetle larvae feed on decaying wood (building up fat reserves, which the adults later rely on. it adds humus and fertility to the soil as its nutrients are released. Though bees and bumblebees (members of the order Hymenoptera) are important as pollinators (of many fruit and crop plants, so are the hoverflies key to  the pollination of many wild flowers.  Hoverflies belong to a different group of insects - the Diptera. There are several thousand hoverfly species spread across the world. They are found on every continent with the exception of Antarctica.  Work by Dr. Wotton and his team at Exeter University suggests they are situations where hoverflies may be more effective pollinators than bees and bumblebees, and the role of hoverflies in crop pollination may have been under-estimated.  Hoverflies can carry pollen over considerable distances, and may  visit isolated plants.  The common drone fly (Eristalis tenax) has been known to travel some 100km and carry the pollen of eight plant species.  Hoverflies (or Syrphidae) are also known to migrate over considerable distances.  The female marmalade hoverfly can migrate from Scandinavia to Spain and North Africa, migrating in the autumn to lay their eggs.  In the following Spring, succeeding generations migrate north again.  Some American hoverflies are known to migrate from Canada to the southern states. Insects are not just important in terms of facilitating decay or aiding pollination, some are involved in seed dispersal.  Scientists at Kobe University studied the dispersal of seeds from the fruit of the silver dragon plant.  Using  time lapse photography techniques, they watched to see which animals feed on the plant’s fruit at night. Whilst crickets (order : Orthoptera) ate much of the fruit, earwigs (order : Dermaptera) and woodlice (not insects, but terrestrial crustaceans) also consumed significant amounts of the tiny seeds of the fruit.  Further work demonstrated that many of the seeds survived the passage through the gut of these animals.  So apart from being seed predators, small invertebrates may also help their dispersal, depositing them away from the parent plant. Woodlice are interesting land based crustaceans that generally feed on dead and decaying plant material, helping in the recycling of nutrients. Further examples of the importance of insects in nature can be seen in fig production.  The fig wasp 'gives its life' in the process of pollinating the fig, in return the fig provides a safe ‘nursery’ for the young on the wasp, seed the woodland blog on the fig.  There are many types of fig and each has its own wasp, to ensure successful pollination.  Full details of the life cycle of fig wasps can be followed here.  The association between the wasps and figs is an example of mutualism. This co-dependence probably had its origin some seventy million years ago, and the wasps and figs have co-evolved since then. .

Though some insects are problematic in that they are carriers of disease (for example, mosquitos and malaria, ticks and Lyme disease); it is nevertheless true that without insects food chains and ecological systems would collapse.  Insects act as  pollinators not just of garden flowers, but of crops,  natural pest control agents (ladybirds eat aphids), Decomposers, breaking down waste products of other animals, remains of dead plants and animals (dung beetles). Their activity ensures the recycling of nutrients in complex biogeochemical cycles. However, as the woodlands’ blog has reported previously, insects (like so many wildlife species) are under threat.  They are in decline due to loss and damage of habitats,  climate change,  pollution and  pesticide use. The decline in insect numbers (in the UK) is ‘monitored’ through BUGLIFE and Kent Wildlife Trust.  Each year a survey is undertaken using the ‘splatometer technique’, in which motorists are asked to record the number of flying insects (e.g. moths, flies, aphids, bees and flying beetles) that are squashed on their front number plate (after a journey).  The length of the journey is recorded, a photo taken and count details uploaded via the BUGLIFE APP, the app includes a tutorial and some safety advice.  Comparing this year’s results of over 6000 journeys with those gathered in 2004 (by the RSPB, who used the same method) reveals a dramatic fall in flying insect numbers.   London, for example, showed a dramatic fall in numbers of 91%.  The fall across England was 83%, Wales saw a 79% drop and Scotland a 76% fall.   Whilst figures for Northern Ireland were limited they suggest a 54% decline. [caption id="attachment_21589" align="alignleft" width="300"] bumblebees favour teasels[/caption] Insects [and other wildlife species] can be helped by: Creating larger areas of natural habitats (many have been lost to roads, agriculture, urban expansion) Creating wildlife corridors to join up similiar habitats/ecosystems throughout the landscape Creating wild flower ‘meadows’ by road sides, verges etc Reducing the use of pesticides and other chemicals which have significant effects on wildlife.  The effect of neonicotinoids on bees and bumblebees is well documented.       

At present, our forests and many across much of Europe have a medley of different species, and this has been the case for many hundreds of years.  They have survived minor fluctuations in climate and weather.  However, now climate and weather are changing in significant ways.  There are more extreme weather events, ranging from unprecedented rainfall to drought and periods of very high temperatures.  Winters seem to be be warmer and wetter, summers hotter and drier. Consequently, there is concern that many tree species being planted today will not be able to survive in the conditions that they are likely to experience in 50 or a 100 years time.  Species like the European Beech (Fagus sylvatica) are likely to struggle (like many did in the heat wave of 1976).  The root system of the beech is shallow, and though it has large roots spreading out in many directions, it cannot access water that may be present at deeper levels in the soil.   Though it is not known how native trees might adapt or be able to respond to a changing climate, it is possible that the number of tree species per km2 able to survive through to the next century may well fall by a third to a half in a warmer climate (depending on how quickly the warming occurs). Examination of some 60 plus European trees species at University of Vienna by Johannes Wessely et al suggested that the English or Pedunculate Oak (Quercus robur) may be a species that could cope with changing climatic conditions. It seems that native UK Oaks are genetically diverse, and this gives rise to variation and the potential to adapt to changing conditions.  Oak is wind pollinated and its light pollen can be dispersed over long distances, which promotes outbreeding and genetic diversity. Whilst the oak has always been valuable as a species for :- Timber production : it is used in furniture making and in the past thousands of oaks were used in the building of ships such as the Mary Rose. Carbon sequestration / storage - it is long lived and has a large above ground biomass Biodiversity : it provides a ‘home’ for many species of animals, plants and fungi. It offers food and shelter for many invertebrate species, numerous insects and spiders); its leaves often show the ‘scars’ of their feeding activities. Its bark is an ideal substrate for many lichen and bryophyte species (epiphytes). The roots of the trees establish mycorrhizal associations with various fungi. Now, the Oak may prove to be valuable in a warmer world as a species for timber production and reforestation projects.  The Oak’s ability to support other plant, animal and fungal species would also be important in terms of biodiversity and resilience..   Forests with a smaller number of tree species are thought to be less resilient to climate change and less biodiverse.   [caption id="attachment_41217" align="aligncenter" width="675"] A solitary oak[/caption]

Large trees are important in terms of carbon storage - with large quantities of above ground biomass, lots of carbon is locked away for years. Trees like Sequoiadendron giganteum, the giant redwoods, are truly large trees;. They are, by volume, amongst the largest trees in the world and incredibly long lived.  Some are thought to be over 3000 years old. Seeds of Sequoiadendron giganteum only arrived in the UK in the 1850’s, brought in by Patrick Matthew and William Lobb.  Lobb was employed by the Veitch Nurseries, based in Exeter.  He travelled extensively in both North and South America (including Argentina and Chile), and brought back not only seeds of the giant redwood but also some 3000 seeds of the monkey puzzle tree (Araucaria araucana).  He made a second trip to South America and brought back many different species of flower, including the chilean bellflower, the flame nasturtium, species of myrtle, and Escallonia macrantha. Exotic trees and shrubs were much prized by wealthy Victorians, and redwoods were planted in the estates and at the entrances of many grand country properties.  They also make appearances in many public parks and gardens, see for example the redwoods at the Lower Pond at Whinfell Quarry Garden in Sheffield. Forestry England estimates that there are half a million Sequoias (giganteum & sempervirens) in the country, and nearly 5000 giganteum trees are recorded by location by redwoodworld.co.uk, the woodland trust ancient tree index and the Forestry Commission.   Though it is only some 170 years since their introduction to the UK, some of these trees are amongst the largest trees in the country. This despite the fact that the climate here is not the same as that on the West Coast of America, their 'natural home'.  Due to their growth rate and carbon sequestration potential, there has been some discussion as to whether they might be included in commercial planting initiatives as they seem resilient to changes in climate, rainfall, soil moisture etc.  Disease resistance in another consideration.  The growth and biomass of some 97 Sequoias at three different sites (Lakehurst, Havering and Benmore) has recently been investigated (using laser scanning)*.  The growth of the trees at Havering was less than that at the other sites, possibly due to lower rainfall (and increased competition) in the East.  However, the growth rates of the trees studied were in the region of 150kg above ground biomass per year (this equates to 81kg of carbon per year).   Such growth is broadly similar to that of their American counterparts of a similar age.  It would seem that Sequoias might be a good choice for planting in terms of carbon uptake.   *Full details of this work here : https://royalsocietypublishing.org/doi/10.1098/rsos.230603    

Many natural ecosystems are periodically exposed to fire.  After a fire, there is often reduced competition and increased nutrient availability (from ash etc.).  The plants and flowers that grow after a fire are visited more often by pollinators, such as bees and other insects.  This can result in increased production of fruits and seeds. Bushfires have been part of certain australian ecosystems for thousands of years and some native species are ‘fire adapted’.  They have come to 'rely' on fires as a means of reproduction and / or  dispersal. Whilst no one fire can be attributed to climate change alone, rising temperatures and aridity, lengthening of the ‘fire season’, combined with bursts of extreme ‘fire weather’, all combine to suggest climate change is implicated. As the frequency of fires increases, the possible benefits of fire to such ecosystems / species are being lost. Fire can help with the physical dispersal of seeds from the parent plant.  In some parts of the world, such as South Africa and Australia, fire and / or smoke can be the stimulus for seed dispersal and subsequent germination.  Plants such as some species of Protea, Banksia, certain members of the myrtle family (e.g. some Eucalypts), and some Pines and Sequoias 'make use' of fire to disperse their seeds. Seed dispersal involving fire is termed serotiny.  Many of these plants produce woody fruits or cones in which the seeds are held.  The mechanism underlying seed release varies but can be due to a resin that ‘seals’ the seeds inside the fruit or cone.  The resin ‘melts’ / liquefies on exposure to heat releasing the seed or there may be a structure called a seed separator (as in Banksia).  Serotinous conifers (like lodgepole pine), have mature cones in which the cone scales are naturally sealed shut with resin.   Most of the seeds stay in the canopy until the cones reach 122-140o F  (i.e 50 to 60oC).  At these temperatures, heat / fire  melts the resin and  the cone scales open to expose the seed. The seed can then drop or drift to a burned but cooling ash-rich soil bed. The seeds do well on the burnt soil available to them as the site offers reduced competition, more light, warmth plus the nutrients from the burning of leaves and litter.  Some species align their germination to immediate post-fire conditions - stimulated by chemicals present in the smoke.  The organic compounds karrikins,  products of the degradation of cellulose are  a germination ‘cue’ for some species.  Karrikins are thought to be present on the soil surface after a fire.  When it rains,  the karrikins are 'washed' into the soil, and seeds present in the soil seed bank are then stimulated to germinate. Thanks to Steve Sangster and John Cameron for images of woodland fire.