Blog - Flora & Fauna
The opening of the woodland canopy.
Certain woodland plants are found in the understory. Plants like wood anemones, woodruff and lungwort bloom early in the year. These plants make use of a ‘window of opportunity’ when the light levels are good as the tree canopy has not developed, the leaves have not yet expanded. They use this ‘window of light ‘ to flower. However, climate change is affecting many ecosystems - including woodlands. With warmer temperatures, leaf buds tend to open earlier and the leaves begin to expand. If the window for growth is reduced, how can the wood anemones and others cope ? [caption id="attachment_38093" align="aligncenter" width="700"] wood anemone[/caption] To investigate this question, scientists based the Universities of Tübingen and Frankfurt examined thousands of preserved herbarium specimens of early flowering plants, dating back over a hundred years. The sheets not only hold specimens collected when they were flowering but also have information on ‘when and where collected’. Each sheet is a a moment in time from over a century ago. Collectively, the 6000+ sheets allowed the scientists to establish historic flowering times of woodland plants over large areas of Europe. [caption id="attachment_38094" align="aligncenter" width="700"] Woodruff[/caption] The information extracted from the herbarium records revealed that plants like wild garlic and wood sorrel now bloom some six days early than at the beginning of the twentieth century. For each 1oc rise in (Spring) temperature, their lowering has advanced by more than 3 days. This means that they have gained time in the light - in an open canopy. Whilst they may have gained time, these early flowering plants are at greater risk of frosts. It may also be that their pollinating agents may not be around - unless they too have brought forward their development / life cycle. There is some evidence that such changes are taking place. Recent work at Wytham Wood (outside Oxford) has shown that blue tits have moved forward their egg laying to 'match' the development of the oak canopy, and the appearance of caterpillars (on which the young are fed). Essentially, the timing of the food chain has changed.. Hopefully, such changes will occur in different ecosystems across the country.
woodlands web updates 16
LASI is the Laboratory of Apiculture and Social Insects at the University of Sussex. It is particularly noted for its research work on bees. Recently, Dr Balfour and Professor Ratnieks have published a study on the rôle of certain 'injurious weeds'. Five of our native wildflowers fall into this category : Ragwort (Jacobaea vulgaris), Creeping or Field Thistle (Cirsium arvense), Spear or Common Thistle (Cirsium vulgar), Curly Dock (Rumex crispus), and Broadleaved or Common Dock (Rumex obtusifolius). They compared the ragwort and the thistles with plants like red clover and wild marjoram (often encouraged / sown on field edges etc).. They found that the 'injurious weeds' were particularly 'effective' at attracting pollinators, not only did they they attract greater numbers of pollinators than clover etc, but also a greater range of pollinator species. This was ascribed to the open nature of their flowers and their generous nectar production. This brings into question the control of species like the ragwort, as it is clearly important to pollinators (as are some 'botanical thugs' - like brambles). Ragwort contains chemicals that are toxic to livestock, causing liver damage; it has been blamed for the deaths of horses and other animals. At the Smithsonian, Kress and Krupnick have analysed the features of some 80,000+ species of plants to see how they might fare in the Earth's changing climate (the Anthropocene). This may seem like a large number of different plants, but represents approximately only 30% of the known species of vascular plants. There is not enough information of the remaining species to make a reasonable guess as to how they might react to climate change; a reflection on how little we actually known about our 'botanical resources'. Sadly, they conclude that more plants will lose out than win. Particularly at risk of extinction are the Cypress family (which includes the redwoods and junipers) and the Cycads, whereas black cherry might be a winner. As was reported previously in the woodlands blog, there is a difference between the leaves of the redwoods found at the top of the tree and those lower down. Those at the top are small, thick, and fused to the vertical stem axis; this fusion of leaf and stem creates a relatively large volume of tissue and intercellular space that can store water. The leaves in the lower part of the crown by comparison are large, flat and horizontal to the stem axis. Now scientists as the University of California (Davis) have further investigated the role of these leaves. They now believe that the different leaf forms help explain how the exceptionally tall trees are able to survive in both wet and dry parts of their range in California. In the rainy and wet North Coast, the water absorbing leaves are found on the lower branches of the trees. In the Southern part of the redwoods range, the water collecting leaves are found at a higher level to take advantage of the fog (and rain, which occurs less often).
A problem with plastic.
In the C19th, many objects were made from ivory. The ivory came from the slaughter of elephants. As elephant populations fell, so the search for a suitable substitute began. Celluloid was one of the first materials used but it was easily combustible. It was soon replaced by other materials like Bakelite, this was the first entirely synthetic plastic. It was made from phenol and formaldehyde. It was used for toys, radios, telephones etc. Bakelite was tough, heat resistant and did not conduct electricity. Other materials followed, and many different plastics are produced today; for example, polyethylene (which is widely used in product packaging) and polyvinyl chloride [PVC] (which is used in construction and pipes because of its strength and durability). The trouble is that plastics are just so useful. Plastics are cheap, lightweight and durable. Durability is a good quality when the plastic is being used but not when it is discarded, for example, into landfill where it may take centuries to degrade. Sadly, many consumers leave empty bottles / containers / wrappers in the streets, on the beach, at picnic sites etc. As most plastics are made from fossil fuels / oil, the manufacture of plastic is also a driver of climate change. Since the middle of the twentieth century, it is estimated that some 8.3 billion tonnes of plastic has been produced. Sadly much of this has ended up in landfill, in rivers, the soil, and the oceans - with significant effects of wildlife. Plastic pollution is ubiquitous. For example, the Great Pacific Garbage Patch, which is a collection of large areas of plastic and other debris in the North Pacific Ocean. It has been estimated that it contains some 1.8 trillion pieces of plastic . It is a serious threat to marine life such as whales, sea turtles, fish, and birds. Plastic items are discarded with little thought to the consequences. Bottles etc can end up as traps for many animals and a few years back we (at woodlands) found a child’s plastic boat dumped in a woodland (see featured image above). Sometimes, we see the distorted remains of plastic tree guards ‘strangling’ young trees. Plastic carrier bags (sometimes filled with dog faeces) can end ups suspended from trees / shrubs in woodland, or caught on wire fencing, waving n the wind. Discarded plastic items come in all shapes and sizes; those that are 5mm or smaller are termed “microplastics.” Microplastics come in part from larger plastic pieces that degrade into smaller pieces; but also from microbeads. Microbeads are very small pieces of polyethylene plastic that are added to health and beauty products, such as some skin cleansers and toothpastes. Now microplastics are to be found everywhere from deep oceans, to Arctic snow and Antarctic ice. They are found in foodstuffs and drinking water. One investigation found that if parents prepare baby formula by shaking it up in hot water inside a plastic bottle, their child might swallow tens of thousands of these microplastic particles each day. The movement of these particles through ecosystems is graphically summarised in this article. There is currently much discussion and research about how these microplastics will impact on the environment and different organisms, including us. Because they are so small and to be found widely in the environment, they enter organisms and food chains. Apart from the plastic in these particles, they may also contain chemical residues of plasticisers, drugs, and pharmaceuticals, and heavy metals may stick to them. Sometimes, sewage sludge may be used as fertiliser and this can contain nanoplastics. Also, treated wastewater is used for irrigation purposes and this again may be a source of plastic. Research indicates that earthworms in microplastic ‘enriched’ plant litter grow more slowly and have a shorter life span, and there is evidence that the gut of earthworms becomes inflamed after exposure to microplastics. Earthworms are important in aerating the soil and transporting materials such as dead leaves from the surface to deeper in the soil, they also 'inadvertently' transport micro-plastics. Springtails, a group of soil micro-arthropods (Collembola) can also help move micro-plastics in the soil. The movement of microplastics through the soil makes these materials ‘accessible’ to other soil dwellers but it is not clear if they pass along food chains (as has been the case with pesticides). Whether nano-plastics are taken up by or affect plants - again is not yet clear. However, the chemicals released by plastics such as phthalates may taken up by plants. There is a significant risk of physical and physiological damage to organisms and ecosystems by these micro-plastics *. The particles also get into the human body and the consequences for our health are, as yet, unknown. further information on nanoparticles etc : https://www.sciencedaily.com/releases/2022/04/220420133533.htm
April Fungi Focus – Chaetosphaerella phaeostroma
In my last post I wrote about inconspicuous ascomycetes – the kind of tiny species that hide in plain site, manifesting themselves as little black dots on dead plant matter such as woody stems. This time, I want to zero in on a species that is not quite so inconspicuous and which grows on dead deciduous wood. After spotting it for the first time this year, it then started popping up everywhere in my local woods and beyond. I’ve found it in three different sites over the past few weeks alone. And not only me, as I’ve seen numerous postings in various online mycological interest groups by people who’d stumbled across it just as perplexed as I initially was. Who knows, perhaps the conditions have been particular good for it this year, or perhaps it’s always been around and I’ve just never noticed it. It’s name is Chaetosphaerella phaeostroma, and though it doesn’t have a common name in English, I’d argue it probably should do, as it is a fairly distinctive species. From a distance, it manifests itself as black fuzzy patches. Up close however, one notices that nestling amongst the felty patches of hairs are dozens of tiny slightly rough textured dark bluey-grey to black spheres up to 0.5mm in diameter. [caption id="attachment_37861" align="aligncenter" width="650"] Chaetosphaerella phaeostroma[/caption] These are the perithecia of this pyrenomycetous ascomycetes – if you didn’t read last months post, these are the hard black spherical flasks that hold the asci sacs that in turn hold and release its spores of this particular group. Looking closely, you can see the top of many of them have broken away, like the tops of Easter eggs. There are many, many fungi species that consists of groups of tiny spherical perithecia like this (to name but a few, there are the various species in the genuses of Nischkia, Ruzenia and Rosellinia, if you care to Google them). But Chaetosphaerella phaeostroma is distinguishable from these due to the coarsely hairy mat its perithecia are immersed in, known as the ‘subiculum’ (defined as the net, felt, or crust-like growth that covers a substrate formed by a mat of hyphae from which fruiting bodies emerge). In fact, there was a time when scientists believe this was two separate species, the orb-like perithecia being one of them, the hairy subiculum being another. [caption id="attachment_37862" align="aligncenter" width="650"] The large distinctive spores of Chaetosphaerella phaeostroma.[/caption] Fungi are complex organisms that constantly seem intent on thwarting those whose attention they attract. So it’s perhaps no surprise to find out that there is actually another species, Acanthonitsckea tristis, that looks superficially much the same as Chaetosphaerella phaeostroma. Whether it is more or less prevalent in the UK, I don’t know, but as ever, the way to tell them apart is through microscopic examination of the spores – the fungi in focus has relatively large (20-25x6-9 microns) banana-shaped ones that are segmented into four with the end segments lighter than the middle two; Acanthonitsckea tristis has much smaller single-celled ones about 6-9x1.5-2 microns. [caption id="attachment_37863" align="aligncenter" width="650"] No hairy subiculum and totally different spores point towards an entirely different genus of Nitschkia for this otherwise very similar looking specimen.[/caption] I duly set about looking for the evidence, laying my find, after removing it from the wood with a penknife, facedown on a microscope slide overnight. The next day, I put the slide under the microscope and found thin curved ones, about 10x2 microns, which fit neither species. I was perplexed for a while, until the ever-helpful Emma Williams of the British Mycological Society pointed out that not only did the spores look more like those of the Common Tarcrust (Diatrype stigma), which I covered in some detail a few years back, or those of a number of other species in the related Eutypa genus, but that Chaetosphaerella phaeostroma doesn’t actually grow on dead deciduous wood, but parasitises these Diatrype and Eutypa species. I had stray spores. [caption id="attachment_37864" align="aligncenter" width="650"] In the top left of this picture you can see Chaetosphaerella phaeostroma growing as a parasite on its host in the bottom right, a member of the Eutypa genus.[/caption] And so I went back to break open the tiny perithecia and tried to ease a new batch of spores out. I was relieved that these did indeed perfectly match the large segmented spores of the Chaetosphaerella phaeostroma I thought I’d discovered. A closer inspection of the original photos also showed that beneath the margins of the felty subiculum, one could see the distinctive pimples of a Eutypa species upon which this was growing. Whereas the Common Tarcrust is fairly easy to identify, the various Eutypa species are not so much. Some grow as a crust with the perithecia embedded in a spreading hard black body (the stroma) on top of the wood, like the Common Tarcust, and some species grow with the stroma forming beneath the wood and the perithecia emerging through it as little black dots. Wikipedia notes this “widespread genus is estimated to contain 32 species”. Even my fairly specialist literature at hand notes only about four species in detail, and I found no records of which might be found in the UK. [caption id="attachment_37865" align="aligncenter" width="650"] This cross-section photo shows the perithecia of this Eutypa species growing beneath the surface of the wood.[/caption] To be fair, such widespread but generally unremarkable types as Eutypa, of which we can find many more examples within the vast understudied field of ascomycetes, are not likely to be of much interest to anyone beyond those who have dedicated their life to the study of such things right down to the level of molecular genetics. I quickly decided it wasn’t worth my losing much sleep over narrowing it down to a species level. However, that they themselves play host to more interesting species like our focus species, Chaetosphaerella phaeostroma, and therefore provide vital clues as to their identification, is more of interest to the amateur mycologist, and points to the complex and little understood interconnectedness of our woodland ecosystems. (I have covered several such examples of fungi-on-fungi relationships previously in these postings, including the Yellow Brain, the Silky Piggyback and the Bolete Eater). The other purpose of this month’s post is also to remind ourselves how surface features of many fungi only get us so far, and that how the complex and unusually-shaped spores of many of the otherwise nondescript ascomycetes can be a handy guiding feature. [caption id="attachment_37866" align="aligncenter" width="650"] The lack of the fuzzy subiculum, the vestiges of white downy hair on the perithecia and in particular the long, worm-like spores guide us to an identification of Woolly Woodwart.[/caption] As an example, I just want to quickly mention another species I found recently beneath a damp, well-rotted deciduous log, the Woolly Woodwart (Lasiosphaeria ovina). The one has an english name, and one that reflects its appearance. While it too grows as tiny spherical perithecia that match the size of those of Chaetosphaerella phaeostroma, these are not immersed in the same black felty subiculum but are typically covered in the woolly white hairs that give it its common name. Except, however, that in the case of the specimen I found, these hairs had worn away, leaving distinctly un-woolly little black balls with little to identify them from without diving into the microscopic realm. Fortunately this was another one with highly unusual looking spores; large, long and worm-like, with dimensions around 40x5 microns, and singled celled – indeed, I initially thought I’d chanced upon a stray nematode on the microscope slide. There are dozens of pages of tiny non-stromatic pyrenometous species listed in my go-to guide Fungi of Temperate Europe (vol 2., to be precise), and many many more unlisted. I hope that the example of Chaetosphaerella phaeostroma shows that not all need a microscope for identification, and that its not worth being too daunted by this group. [caption id="attachment_37867" align="aligncenter" width="650"] Chaetosphaerella phaeostroma[/caption]
It would seem that pollinators have ‘favourite plants’. Research centred on the National Botanic Garden of Wales has looked in some detail at the foraging habits of bees, bumblebees, hover flies and solitary bees - our most important pollinators. Dr Abigail Lowe identified the plants that the insects were visiting by analysing the DNA from pollen grains on their bodies (a process known as DNA barcoding). It is clear that the ‘preferences’ of the insects change with the seasons and indeed the availability of particular flowers. In Spring, nearly all the pollinators frequent buttercups, lesser celandines and dandelions (all brightly coloured yellow flowers). Come the summer, honey bees and bumblebees tend to favour thistles, knapweeds and brambles, whilst hover flies may be seen on hogweeds and angelica plus thistles and knapweeds. In autumn, the bumblebees can be see visiting asters (Daisy family flowers) and brambles. Full details of her work can be found here : https://botanicgarden.wales/press/plants-for-pollinators-new-dna-research-reveals-fascinating-insights-into-the-plants-used-by-bees-and-hoverflies/ [caption id="attachment_27033" align="aligncenter" width="600"] Pollen dusted bee on sunflower[/caption] There are also suggestions on how to help pollinators in your garden, such as encourage buttercups and dandelions by reducing mowing (in the Spring) plant late flowering daisy type flowers encourage some bramble (you might get some blackberries, in return) reduce the use of chemicals (especially pesticides and herbicides) hoverflies can be encouraged by damp, wet areas and rotting wood and these suggestions would also work in a woodland.
March Fungi Focus: Bracken Map and other Little Black Dots and Smudges
There are times when one does begin to wonder whether one has tumbled too far down the rabbit hole of mycological obsession. Though the Spring months might seem something like a drought period for many in search of curious fungi, they are all around us and all year round. For the hardcore few, the next few months in particular are a time of rummaging through hedgerows and peering at dried twigs, grasses and herbaceous stems in search of what effectively appear as little more than black dots. From then on, it is a just a small step away from the full-blown insanity of lichenology. This month’s focus is on the more common and recognisable of these obscure types, which all fall within the category of ascomycetes: these are the spore-shooter types that develop their spores internally, typically in tube or flask-like sacs and in batches of eight, as opposed to the basidiomycetes, where the spores grow externally on cell-like structures known as basidia, typically in groups of four, which drop off as they mature. Patellaria atrata, growing as inconspicuous black dots on a dead fennel stem, with the spores arguable more interesting looking than the fungus itself. I’ve written quite lengthily about various groups of ascomycetes in previous posts, but despite the fact that they far outnumber the basidiomycetes in terms of prevalence and the proliferating number and variability of species – which include the colourful goblet-shaped Green and Turquoise Elfcups, the hard black woodwarts and tarcrusts, and other less noticeable things like Sycamore Tar Spots and Holly Speckle) – many consider them a no-go area due to the inedibility of the majority of them, not to mention the fact most are very difficult to even see, unless one is looking specifically for them, yet alone identify. Few have common names, and even the Latin names change with alarming regularity as individual species find themselves reclassified or split up into numerous subspecies. The obvious exception here is that prized edible, the Morel (Morchellan esculenta, although there are a few other lookalike species), one of the few that make it into spotters guides and foragers handbooks. The spores of Bracken Map developing within its ascus, with their characteristic crescent shape, relatively large size and multiple segments. To really get to grips with the subject would take the kind of life-long fanaticism and fastidiousness displayed by the likes of Peter Thompson, the author of Ascomycetes in Colour (2013), who has evidently spent years driving around the country in search of photographic examples of the numerous nondescript specimens that can be found on specific hosts such as dead grasses, leaves and other organic material. It took literally a lifetime of research before the husband and wife team of Martin B. and J. Pamela Ellis devoted their retirement from teaching to put pen to paper for their landmark Microfungi on Land Plants: An Identification Handbook, first published in 1985 with a revised and enlarged edition appearing in 1997. Though it’s technically been out of print for years, the book remains a must-have for serious mycologists, giving an exhaustive list with detailed illustrations of the type of species one might find on a wide array of specific hosts, and secondhand copies are accordingly pricey. There’s also been more recent scholarly books such as Bjorn Wegen’s up-to-date and even more comprehensive Handbook of Ascomycota (2017), but again, this is a specialist publication intended for an academic readership and priced beyond the range of all but the most curious of amateur naturalists. The foreword of the revised 1997 edition of Ellis and Ellis refer to microfungi as “ones which require the use of a microscope to see their variety”. Nevertheless, a microscope isn’t always necessary for the identification of a number of common types if you can ascertain their host. For example, over the next few months, if one looks closely at dead nettle stems, one might spot the tiny tangerine-coloured fruiting bodies (ascocarps) of Calloria neglecta, an ascomycetes fungus specific to them. Two very similar looking species grow on ash keys: Diaporthe samaricola, grows on the seed part; the smaller Neosetophoma samarorum only grows on the winged part. An even more extreme example of host specificity is Diaporthe samaricola, which over the winter months appears as miniscule black dots, less than half a milimeter in diameter, on the dried winged seeds, or keys (‘samara’) of ash trees. However, they will only appear on the seed part of the ash keys. Another fungus, Neosetophoma samarorum, produces eruptions of even smaller dots on the winged parts of the keys. The two will often appear side by side. They have no adverse affect on the health of the tree in question, although there is another ascomycetes that does have a notoriously detrimental effect on its host - Hymenoscyphus fraxineus, responsible for Ash Dieback and detailed in a previous post. Its small, white nail-shaped fruitbodies can be found on the blackened twigs and petioles at the foot of the infected tree around June. Bracken Map (Rhopographus filicinus) is another commonplace and instantly recognisable species that is host specific. It can easily be spotted at this time of year in most places where you find dead bracken, just prior to a new season’s growth sprouting up to replace the last, but actually one can find it all year round. The reason for its name is self-evident, as it grows in elongated spreading black blotches that eventually merge to form irregular shapes like countries on a map. Dead bracken stems throughout the year can be seen hosting the tell-tale ascocarps of the Bracken Map. These blotches are the ascocarps, the fruitbodies from which the spores are released. The are described as pyrenomycetous, meaning that like the tarcusts or woodwarts or commonly-spotted Cramp Balls (Daldinia concentria, aka King Alfred’s Cakes), they are hard, brittle, and often carbonaceous, optimised to continue releasing spores over a relatively long period of time during the late-winter and spring months when the weather is relatively dry and temperatures start increasing, and yet there’s little greenery about to shelter them from the dry wind and lengthening hours of sunlight or get in the way of spore dispersal. Each of these fruit bodies contains numerous tiny ‘perithecia’; flask shaped pits in which the asci sacks and the spores that develop within them are housed and are kept from dessication. The spores are released from holes known as ‘ostioles’ in the top of the perithecia that cover the black surface of the Bracken Map. If one looks really closely, one can see that the ostioles in the case of the Bracken Map are elongated along the length of the bracken stems. The ostioles from which the spores are released can just about me made out when the ascocarp is looked at extremely closely. The shape of the ostioles are a key feature in identifying other pyrenomycetous fungi, as detailed in my 2020 post on Woodwarts, Blackheads and Tarcrusts. It’s just as well, because there are many other types of such fungi that are not quite as distinctive-looking as the Bracken Map, and often much much smaller. I’ve been scrutinising various hedgerows recently, and noting that despite their superficial similarities, the seemingly identical black dots that appear on, for example, elder or hawthorn, are often very different species from those that appear on the woody dead stems of clematis or hogweed or other plants. Fortunately, for those with a microscope, these kind of ascomycetes do have very distinctive spores that often serve as much better means of identification, in consultation with the literature cited above, than the actual ascocarp fruitbodies. As mentioned, basidiomycetes produce their spores externally on basidia, growing like apples from trees almost, and so they are typically asymmetrical and one can note the vestiges of a kind of stem by which they were attached to the basidia. The ascospores of ascomycetes tend to be much more symmetrical, often much larger and in some cases much more complex, consisting of multiple cells in different arrangements. These tiny specks on a dried hogweed stem could be anything, but the complex multi-celled spores compare with a species called Pleospora phaeocomoides. The spores of the Bracken Map are a great example of this – they are 27-35x7-8 microns in size, making them about three to four times the size of a typical mushroom-shaped basidiomycetes type like a Brittlegill – and to put this in perspective, they are just a smidgen smaller than the 40-micron threshold considered visible to the naked eye, or about the size of a small grain of salt. They are crescent shaped with 4-8 segments, and look rather like croissants under the microscope. I’ve detailed a scant few of these types of fungi prevalent over the next few months that can at least be recognised without recourse to a microscope. There are, however, at least 10,000 ascomycetes species found in the British Isles alone, so this is clearly a subject few will want to engage with too thoroughly. There are a couple of other more readily identifiable species that might catch the attention of the woodland walker, however, but I’ll leave these for next month... Bracken Map
Fire and forests.
There is evidence that trees lost to fires and drought are not returning to fire damaged areas. Fire has been ‘part and parcel’ of the dynamics of some forest ecosystems. The fires take out smaller trees, giving space and light to others. Fire (or the smoke associated with it) can even help the seeds of some species to disperse and/or germinate (eg. serotiny in certain Pines). Different chemicals from smoke such as karrikinolide and glyceronitrile are known to play key roles in smoke-stimulated germination of certain species, such as heather. However, climate change is affecting forests (and woodlands) across the globe. Fires are becoming more frequent (associated with increasing drought) and trees are struggling to return / regenerate after intense or repeated fires. An analysis of a number of sites in the Rocky Mountains suggests that in some areas fire, moisture stress and increasing temperatures result in a loss of resilience so that forested areas are being replaced with shrubs, grassland and flowers. "Fire refugia" are areas that somehow avoid significant or frequent damage; they burn less often and/or less intensely than the surrounding landscape. Such areas are important in the recovery of the ecosystem after a fire - allowing re-population of the area with a variety of species. [caption id="attachment_35352" align="aligncenter" width="650"] Woodland recovering from a fire[/caption] Consequently, studies have been directed towards understanding the physical and biological nature of such refugia. The work has focused on mature, conifer dominated forests in the States (The Klamath-Siskiyou region) and the fires that have occurred over a period of some 30 years. It was found that refugia were associated with physical features of the habitat such as rocky outcrops, depressions in the landscape. It was also noted that the density of the smoke that the fires generated was a factor in tree survival (perhaps dense smoke offered a degree of shade?). The area studied has a complex and diverse geology, with varied habitats that support considerable biodiversity. Fire has always been a key factor in the maintenance of the varied landscape but with the climate becoming hotter and drier, there is concern that an increasing frequency of fires will ‘eat away’ at the forest’s ability to regenerate - with the loss of refugia and incineration of seed banks in the soil. Severe fire can reset the path of succession - so that forest can be reduced to bare soil. Complex and established communities of fungi, microbes, plants and animals are lost, reduced down to bare soil. Intense heat will damage the structure of the soil, reducing its organic content and its complex community of microbes. In extreme cases, this can lead to the erosion of the soil.
Changing forests and woodlands.
For millions of years, forests and woodlands have been changing - as a result of natural regeneration, storms, fires and climate change. However, with the expansion of human populations, woodlands and forests have been cut down to make way for towns, cities and the infra-structure of ‘modern’ life. Sadly forests, and woodlands such as those in the path of HS2, are still disappearing. ‘Untouched’ rain / tropical forest is being cut down to make way for cash crops; plus vast wooded areas have been destroyed by fire in Australia, Sweden and on the West Coast of the United States in recent years. Clearfell of any forested area for timber or agriculture involves the removal of all trees / vegetation and is sometimes followed by burning of the remaining debris. Clearfell can also have unintended consequences (beyond the loss of entire animal communities. An Australian study has shown that it lowers soil nutrient levels - notably nitrate and phosphate. Furthermore, the use of heavy machinery in clearfelling can compact the soil and its consequent exposure to the elements can lead to erosion (rain runoff). When an area is subject to intense fire, there is a drop in the organic carbon content of the soil and structural damage to the soil; it can take many years for such fire-damaged soil to ‘recover’. Forests and woodlands support the vast majority of land-based species. However, the species that we see today on a woodland walk may be different to those our ancestors might have seen five hundred or a thousand years ago. Certain species only survive in relatively undisturbed (and ancient) forests / woodlands. There are species that can ‘deal’ with disturbance and are adaptable, indeed opportunitistic, such as red deer and fox. The same can be said for certain plants species, which can become invasive. Changes in species make-up and biodiversity do not always immediately follow loss of forest or woodland. Generally speaking, the longer the life span of a species then the longer for the effects of forest loss to become apparent. It may be that the effects ‘span’ generations, raptors / birds of prey may manage to raise their young in the immediate period following loss of forest or woodland. But their offspring may struggle to survive in a depleted environment. It might be that with limited resources an animal might simply not reproduce for years, if ever again. Consequently, the impact of forest destruction / loss that species depletion might not be apparent for many years. The loss of forests and woodlands has lead to many local, national and inter-national initiatives to offset these losses: for example, New Zealand’s ‘One Billion Trees” project and the Nature Conservancy’s “plant a billion trees’ campaign. Broadly speaking, reforestation involves the planting of native trees in an area, whereas planting with new (non-native) species is afforestation. Recent research suggests that whilst non-native plants often grow faster than native species, they also have less dense tissues (think: oak versus larch) and decompose more readily, which can contribute to more rapid cycling of carbon. This will not help to mitigate climate change. It is also important to consider which trees might prosper and offer resilience in the light of climate change. Our climate is changing and will be different in the future, with summer temperatures being higher. We have already seen more extreme weather events (leading to flooding and wild fires). Forestry England has a number of tools to help plan which tree species will be suited to a site, now and in future. There is ESC4 which offers a means to help forest managers and planners select tree species that are ecologically suited to particular sites; and there is also the climate matching tool. As Forestry England says this is “so that we can see which places in the world currently experience the climate we are projected to have in future. We can compare these different places to help us plan which tree species will be suited to a site, now and in future”. One strategy is to create woodlands that are more diverse, as it thought that diversity helps woods more resilient to climate change. This can be through encouraging a range of different, but carefully selected trees to grow, and being aware of the provenance of seeds or saplings.