Kveldssanger

Somtimes I do wonder how I ever live with myself!

It seems there is. Pages 97-101. Some really good pictures, and some good accompanying text. By no means extensive, though there are probably a few bits I could have added to my coursework / subsequent blog post. Not sure why I didn't consult it when writing it, to be honest.

Sweet photos, David!

I shall check!

01/03/16. Fact #164. The utilisation of a device that creates a wound means that the locally-exposed surface can be readily colonised by a pathogen, thereby meaning decay propagation around the wound area and then further beyond is possible – particularly if the tree cannot compartmentalise the wound effectively. If the tree is already weak, which may likely be the reason for such an investigative practice (to determine extent of decay), decay has an even higher probability of either setting in or further propagating. Furthermore, the deeper the wound, the more potentially significant the wound becomes in terms of decay onset and facilitating succession into surrounding areas – small, shallow holes that span no further in than two growth rings are the lowest risk, followed by narrow holes that delve deeper into the wood (Johnstone et al., 2010; van Wessenaer & Richardson, 2009; Watson, 2006; Weber & Mattheck, 2006). Species-specific traits in relation to CODIT do of course dictate how decay may develop (Shigo, 1986; Shigo, 1991), though artificial drilling (or the removal of bark plates) is never beneficial from an energy perspective as the discolouration of wood local to the wound means less wood is available for the tree to store energy, in addition to the potential onset of decay and the consequences incurred thereafter. It is important to recognise that decay organisms can travel down a bore hole and propagate further within the tree as a result, albeit on a local scale initially. Over-frequent boring can therefore exacerbate instances of decay – particularly as it breaks the natural barriers formed by the tree to stop further decay from occurring (reaction and barrier zones) that may have been laid down in response to pre-existing decay (Lonsdale, 1999; Schubert, 2007; Weber & Mattheck, 2006). Further, the larger the bore hole the greater the risk, on average, of decay onset or propagation (Kersten & Schwarze, 2005). Species that lack true heartwood may be more susceptible to the adverse effects of drilling, because their ‘heartwood’ does not have the extractives that react with oxygen as a mode of defence against pathogenic invasion (Shigo, 1991). Polyporus squamosus, for example, was found on half of the specimens subjected to increment bore holes during one study. As a fungal species that has a strategy that involves entry via stem wounds, such bore holes may provide conditions for germination of its fungal spores (Kersten & Schwarze, 2005). Such an observation can act as a proxy indicator for similar fungal strategists, that too employ such a tactic for entry. Curiously, the study suggests that certain fungal species might be adversely impacted by the presence of bore holes, given the conditions created as a result of such boring. In this study, Inonotus hispidus was found to have limited radial outgrowth around areas of boring damage sustained by an increment borer (that creates larger holes up to 10mm), whilst not having limited radial outward growth from damage via the IML-Resistograph (that creates much smaller holes). This may be to do with Inonotus hispidus having a preference for low-oxygen, high-carbon dioxide conditions, which other decaying fungi are also adapted to – these conditions are not present when bore holes are larger. In this longitudinal cross-section of ash (Fraxinus excelsior), we can observe how the tunnel created by the increment borer has led to discolouration around the wounded region. The hole itself, though only within the reaction zone region, has also been filled by a mycelial plug of the shaggy bracket fungus (Inonotus hispidus). Such a mycelial plug keeps conditions right for fungal decay, which would have been temporarily altered (adversely) by the creation of the tunnel courtesy of the removal of a wood core. Source: Kersten & Schwarze (2005). With regards to micro-drills in particular, and for other devices that bore into the wood, shavings created from the drill’s passage through the wood can sometimes be displaced along the bore tunnel, thereby directly aiding with internal propagation and the spread of decay organisms (Axmon et al., 2004; Johnstone et al., 2010; Kersten & Schwarze, 2005). Research has nonetheless concluded that such decay onset from micro-drills is typically short term (8-10 years), after which point compartmentalisation had fully completed. In trees that were tested that had no evidence of decay there was no onset of decay post-drilling (Kersten & Schwarze, 2005; Shigo, 1986). Concerns should however manifest when boring into trees with existing decay, as drilling can, as established, facilitate fungal progression into sound areas of wood. How drilling with a resistograph enabled the decay from honey fungus (Armillaria sp.) on black poplar (Populus nigra) to propagate outwards along the boring tunnel. Source: Weber & Mattheck (2006). One must also note that vascular tissue will be damaged during the boring process, which can impact upon hydraulic conductivity and efficiency of the tree’s vascular system by default, in addition to the fact aeration of the xylem and subsequent risk of xylem dysfunction (and subsequent decay onset) will potentially manifest. This is particularly an issue where dulled drill-bits are used – if drilling is necessary, very sharp drill-bits must be utilised. Caution must also be exercised so that, when preparing for drilling, no pulling or twisting movements to remove bark are undertaken, in addition to not drilling when bark is loose in the spring and autumn, and not plugging or dressing the drill holes (Johnstone et al., 2010; Kersten & Schwarze, 2005; Shigo, 1991). Such aforementioned practices can facilitate in the creation of more expansive decay regions, either by providing entry or making site conditions preferable for rapid succession. In addition, bore hole presence can provide conditions for cracks to propagate laterally out from the hole (Shigo, 1986). This can bring about a situation where future failure or weakness can establish and / or cracks can propagate under mechanical stress, caused initially by the presence of the bore hole (Weber & Mattheck, 2003). Ultimately, unless the invasive increment leaves a spindle-shaped hole, the force-flow of the wood grain locally will be interrupted in a manner that detracts from equal stress distribution (Mattheck & Kubler, 1997). The presence of a bore hole (which cannot possibly leave a spindle-shaped tunnel) might therefore impact upon the structural integrity of the tree, given acute stress build-up. Invasive techniques also require human operation for large portions of the process, and thus the process is open to human error more so than in computerised techniques – i.e. a radial core sample may not be a true radial core sample and thus a second sample may need to be taken, and if a sample is being taken and assessed for decay via feel, smell, etc, then it is open to more subjectivity and prognosis might be incorrect. Computerisation brings about objectivity and improved accuracy, which is critical when looking to determine internal wood decay (Nicolotti & Miglietta, 1998). Human error can simply lead to unnecessary (further) wounding, which will have adverse impacts upon the health of the tree that, given the reasons behind invasive tests, will likely already be under stress. Shigo (1986) even suggests that, if boring is necessary, the operative should practice on a fallen log first. The financial cost is generally relatively acceptable for many invasive devices, though particular devices may cost tens of thousands of pounds. However, the modest cost does not make up for the need for operators to be properly trained and knowledgeable in the interpretation of the results from the device. If operators are not skilled in the device they are using, not only may the tree be falsely-diagnosed but, as previously mentioned, additional invasive tests may need to be undertaken to obtain the required readings. Additionally, notably for drills, the only decay that will be detected is along the bore tunnel – decay pockets could be missed by a fraction of an inch and thereby avoid detection (Nicolotti & Miglietta, 1998). A skilled operator will be more likely to successfully bore into the correct areas after fewer attempts. Weighing up the cost versus the benefits really doesn’t paint such invasive techniques as ultimately good for health of the tree, in light of the aforementioned points. However, the ease of use of many invasive methods, when compared alongside accuracy (critical for the safety levels of trees in urban areas, in particular), cost, and reduced implications to tree health with their appropriate (not excessive) use, can justify their utilisation without significant concern (Johnstone et al., 2010). Of course, for specimen trees or trees that are otherwise deemed critically important, non-invasive (or minimally-invasive – the PICUS Sonic Tomograph) means of decay-detection might be preferable – thermal imaging may be the chosen option in such a scenario (Catena & Catena, 2008). References Axmon, J., Hansson, M., & Sörnmo, L. (2004) Experimental study on the possibility of detecting internal decay in standing Picea abies by blind impact response analysis. Forestry. 77 (3). p179-192. Catena, A. & Catena, G. (2008) Overview of Thermal Imaging for Tree Assessment. Arboricultural Journal. 30 (4). p259-270. Johnstone, D., Moore, G., Tausz, M., & Nokolas, M. (2010) The Measurement of Wood Decay in Landscape Trees. Arboriculture & Urban Forestry. 36 (3). p121-127. Kersten, W. & Schwarze, F. (2005) Development of Decay in the Sapwood of Trees Wounded by the Use of Decay-Detecting Devices. Arboricultural Journal. 28 (3). p165-181. Lonsdale, D. (1999) Principles of Tree Hazard Assessment and Management (Research for Amenity Trees 7). London: HMSO. Mattheck, C. & Kubler, H. (1997) Wood – The Internal Optimization of Trees. USA: Springer. Nicolotti, G. & Miglietta, P. (1998) Using High-Technology Instruments to Assess Defects in Trees. Journal of Arboriculture. 24 (6). p297-302. Schubert, S. (2007) Acousto-Ultrasound Assessment of Inner Wood-Decay in Standing Trees: Possibilities and Limitations. PhD Dissertation (Diss. ETH Nr. 17126). Swiss Federal Institute of Technology, Zürich. Shigo, A. (1986) A New Tree Biology. USA: Shigo and Trees Associates. Shigo, A. (1991) Modern Arboriculture. USA: Shigo and Trees Associates. van Wessenaer, P. & Richardson, M. (2009) A Review of Tree Risk Assessment Using Minimally Invasive Technologies and Two Case Studies. Arboricultural Journal. 32 (4). p275-292. Watson, B. (2006) Trees: their use, management, cultivation, and biology. India: The Crowood Press. Weber, K. & Mattheck, C. (2003) Manual of Wood Decays in Trees. UK: The Arboricultural Association.

28/02/16. Fact #163. Birds are without doubt the principal means of seed dispersal by animals, and trees that produce fleshy fruits are typically reliant upon such dispersal means to expand their geographical ranges. Ornamental trees that produce fleshy fruits grown within urban locations, which are not necessarily native to the area in which they grow, may therefore also benefit from such a dispersal mechanism and begin to succeed into the surrounding environment. Granted, frugivorous birds within urban environments may behave differently to birds within woodland stands (or other ‘natural’ setting), and not much is known about the foraging preferences of such birds in the urban setting. Despite this, it is considered that the colour of tree fruit is one driver influencing upon attracting birds, because of the good vision of birds (to make up for their poor sense of smell). In this study, the authors investigate how the preference of birds to the fruits of Ilex aquifolium cultivars (and the standard Ilex aquifolium) growing within urban environments has impacted upon the dispersal of seed, and in turn enabled the species to advance into previously uncharted territory within northern Europe. Because the main dispersal mechanism of the species’ seed is via birds, understanding what fruit characteristics (colour, size, etc) influence avifaunal frugivory is important. By the same token, do birds preferentially select cultivated Ilex aquifolium, or instead opt to consume the fruits of the native non-cultivated species? Similarly, understanding what site qualities attract birds can help to improve understanding of the dissemination of Ilex aquifolium into the surrounding landscape. Because the natural range of Ilex aquifolium reaches its north-eastern climax in Denmark, the study site was located around the current climax zone (within Greater Copenhagen). Within this area, six sites were selected, of which three were cemeteries and three botanic gardens – all within urban areas. Over the past few decades, this climax zone around had been relatively stable, until more recently (since the turn of the millennia) when it was observed to expand its range by a distance of 100-200km up into Greater Copenhagen. Such a shift, the authors remark, would be down to the more favourable climatic conditions, though would be facilitated by seed dispersal courtesy of frugivorous birds. To investigate if birds had different preferences with regards to fruit from different cultivars, the following cultivars were used within the study: ‘Bacciflava’ (strong yellow fruits, in clusters of 3-5, and 8mm in diameter), ‘Crinkle Green’ (vividly red fruits, in clusters of 1-3, and of 7-9mm in diameter), and ‘Pyramidalis’ (vividly red fruits, in clusters of 1-4 and of 8-10mm in diameter). The standard Ilex aquifolium fruits also featured, in order to compare cultivars to the standard (and native) holly species. To understand the fruit properties of all four hollies used, samples were taken from the individuals from which branches were sourced for the study, and the maximum diameter of the fruits, the fresh mass of the fruits (pulp:seed ratio), and water content were measured. Ilex aquifolium ‘Bacciflava’. Source: University of Richmond. From the three cultivars and the native species, branches containing fruits were sourced (within Denmark) and placed at the six locations (from December to February). All branches had similar qualities, possessing 10-20 leaves and fruits, and were fixed to identical wooden boards atop a 1.6m wooden stick to expose the fruits to birds exclusively. Five of these boards were set up in open areas at least 5m away from trees over 3m in height, and five were set up under trees and tall shrubs over 3m in height. Over the course of the survey period, the branches were all checked 15 times, and records gathered as to how many of the fruits had been taken from each sample. Once the survey was completed, it was found that birds (blackbirds and robins) had eaten 2,655 of the 3,404 (78%) fruits across all four branch types. However, the rate at which the fruits were removed varied between branches, with ‘Crinkle Green’ having its fruits removed most abundantly. In terms of the total number of fruits removed from each branch type, the cultivar ‘Bacciflava’ massively reduced the average by having only 35% of its fruits removed. ‘Crinkle Green’ had 94% of its fruits removed, ‘Pyramidalis’ 92%, and the native holly 91%. Therefore, it is evident that birds had a strong preference for red-coloured fruits (fruit of ‘Bacciflava’ was a green-yellow in colour), though there is little evidence to suggest there is any preference as to what fruits were eaten beyond mere red colouration. There was also a marked difference in the rate at which fruit was removed from the different feeding station locations, with branches under trees having their fruit removed at a much higher rate than those in exposed settings. Ilex aquifolium ‘Pyramidalis’. Source: Helmers. In light of the results, it can first be noted that birds did eat the fruits from all four branch types and across both feeding station locations (exposed and sheltered). Therefore, there is potential for many Ilex aquifolium cultivars to enable for seed dispersal and the associated expansion in the native range of the species. Granted, red fruits were eaten far more readily, and this suggests that cultivars with red fruits (and the red fruits of the standard Ilex aquifolium) are far more appealing to birds. It must of course be noted that other fruit colours, such as white and orange (which some Ilex aquifolium cultivars have), were not used within this study, and therefore all that can be ascertained is that red fruits are more desirable to birds than green-yellow fruits. Looking beyond fruit colour, it can be said that smaller fruits are removed more readily by birds. This is because ‘Crinkle Green’, which had 94% of its fruits removed, possessed the smallest fruits. Such a finding does however conflict with the understanding of larger fruits being more desirable to birds (up to a point, when fruits become too large to fit within a bird’s beak), and particularly earlier in the fruiting season of Ilex aquifolium. The pulp:seed ratio was however shown not to be an influencing factor, as ‘Crinkle Green’ in fact had the lowest pulp:seed ratio, whilst the second highest branch type from ‘Pyramidalis’ had the highest ratio. Building upon this, because the nutritional profile of fruits was not measured, it is difficult to make the assertion that the amount of flesh on a fruit is significant in determining bird frugivory. It may very well be that birds seek nutritional fruits, and these fruits may very well have varying pulp:seed ratios. A robin perched upon the branch of an Ilex aquifolium. Source: Warren Photographic. In terms of the amount of fruit per branch, because the number of fruits was relatively similar across all branches (10-20 fruits on each branch), there was little data to support claims that the abundance of fruits influences upon bird frugivory. Of course, if entire specimens were studied, then it may very likely be found that fruit abundance does influence upon frugivorous birds. In fact, other research has shown exactly this, and the authors remark that Ilex aquifolium cultivars that produce more fruits will hasten the species’ expanding range by attracting birds more readily. The fact that birds also more routinely ate fruits from branches sheltered by the canopy of trees and tall shrubs is also telling. From an evolutionary and habitual perspective, this is not surprising, because birds will utilise the cover to reduce the risk of predation whilst they are foraging for food. An open environment leaves the bird exposed, and therefore if fruits can be obtained in sheltered settings then that is much preferred. Such a preference is actually quite beneficial for Ilex aquifolium, the authors allege, because it is a shade-tolerant species that can readily exist beneath tree canopies. By this token, the habit of birds eating fruits from sheltered hollies in urban areas may enable the species to expand its range by using urban woodland sites (and other sheltered locations) as vectors. Therefore, it can be said that, if an Ilex aquifolium is to be planted within an urban setting then it is to be located in an exposed area, and should not have red fruits. Granted, this is assuming that its northward spread is not to be desired. Furthermore, because the survey sites were only in botanic gardens and cemeteries, there is a failure in recognising how small to medium-sized gardens within the urban and sub-urban setting may impact upon bird frugivory and the subsequent dispersal rate of Ilex aquifolium. Nonetheless, the results are interesting, and there is certainly scope for considering what types of cultivar to plant within an urban environment if succession of the species is of concern. This applies not only to Ilex aquifolium, but across the entire botanical spectrum. Source: Møller, L., Skou, A., & Kollmann, J. (2012) Dispersal limitation at the expanding range margin of an evergreen tree in urban habitats?. Urban Forestry & Urban Greening. 11 (1). p59-64.

Oh, indeed! Got a Kickstarter page up to get funding for a vaccine to cure it, but until then it's photos and books galore! I stand by what I said, as well. I saw more fungi on the Heath in one day than I did in nearly an entire year where I work. That's the beauty of established woodland stands and veteran trees, I guess!

I echo what others have said. He couldn't be learning at a better place. I take it he's already adept in fungal ident'?

Perhaps reading Common Sense Risk Management of Trees will help, with regards to understanding risk. Link here.

Trying to find a role in an LA is tough, as LAs cannot unfortunately make jobs out of thin air in this day and age (not that they necessarily ever did). Finding consulting work is also quite tricky I would image, unless you have some experience under your belt. Working as a volunteer for an LA is good, though your scope for learning is limited in such an environment as I'm not sure if an LA can divulge all information relating to works issued, etc. Have a read of BS 3998, perhaps? There's an uncontrolled PDF copy floating around online, if you search.

Cheers, Sean. Glad it's of use to people other than myself!

27/02/16. Fact #162. Antitranspirants are products that, when applied to foliage, reduce the rate of foliar transpiration. Comprised of a wax, plastic, or resin, the application of an antitranspirant leaves a thin, protective film atop the leaf surface (Brent-Jones, 1966; Watson & Himelick, 1997; Watson & Himelick, 2013). The film may last for several weeks, though re-application is necessary if there is a desire to reduce transpiration rates for elongated periods of time. Furthermore, if leaves are still growing then the film will crack and its efficacy will be reduced as a result (Watson & Himelick, 2013), meaning application prior to the leaves being fully-grown is perhaps not wholly effective. In addition to this, as the spray dries to become invisible, there are no means to ascertaining how much has been applied or retained upon the leaf at any given time, and nor is there a way in which the extent of cracking can be ascertained (Brent-Jones, 1966). When used improperly (applying too much and potentially also at overly-frequent intervals), application of an antitranspirant may be detrimental to plant health. Reductions in root and shoot growth may be observed, in such instances (Lee & Kozlowski, 1974; Watson & Himelick, 1997). However, when used properly, their application can increase growth rate and aid with plant establishment via the retention of more water (Davenport et al., 1972; Steinberg et al., 1990). There is also distinct variability in the efficacy of different products, though not only do the products themselves differ but differing environmental conditions, as well as different species, result in varying levels of efficacy across product ranges and also within the same product (Hipps & Nicoll, 1997; Watson & Himelick, 2013). For instance, on species including the pines (Pinus spp.), application can significantly reduce transpiration (by bolstering the already waxy leaf surface), though can also reduce the rate of photosynthesis very markedly; mainly due to reduced CO2 diffusion (Davenport et al., 1974; del Amor et al., 2010; Kozlowski & Davies, 1975; Watson & Himelick). When applied to some species, certain antitranspirants are also toxic. Because application of an antitranspirant reduces transpiration, leaf surfaces may also potentially warm up considerably more during warmer periods. This can damage the leaf tissues, and result in dysfunction through injury (Watson & Himelick, 2013), leading to early senescence of leaves that have become damaged (Neumann, 1974). Root and shoot growth may therefore be impacted negatively, in response (Ranney et al., 1989; Wellburn et al., 1974). Such products are nonetheless useful for regulating water loss post-transplanting (Berkowitz & Rabin, 1988), and may be particularly effective during the spring months (Harris & Bassuk, 1995). However, the reliance on such products should not replace good transplanting practice (Watson & Himelick, 1997), and care should be used when applying any type of antitranspirant. It is preferable to apply an antitranspirant only lightly, for an overall net benefit in response to an application (Watson & Himelick, 2013). Granted, it should be noted however that once water availability within the soil reaches the lowest critical threshold, even the application of an antitranspirant is of no aid (Steinberg et al., 1990). It may therefore be wise to combine such application, in times of significant drought, with irrigation. References Berkowitz, G. & Rabin, J. (1988) Antitranspirant associated abscisic acid effects on the water relations and yield of transplanted bell peppers. Plant Physiology. 86 (2). p329-331. Brent-Jones, E. (1966) Some aspects of moving semi-mature trees. Arboricultural Association Journal. 1 (3). p71-76. Davenport, D., Fisher, M., & Hagan, R. (1972) Some counteractive effects of antitranspirants. Plant Physiology. 49 (5). p722-724. del Amor, F., Cuadra-Crespo, P., Walker, D., Cámara, J., & Madrid, R. (2010) Effect of foliar application of antitranspirant on photosynthesis and water relations of pepper plants under different levels of CO 2 and water stress. Journal of Plant Physiology. 167 (15). p1232-1238. Harris, J. & Bassuk, N. (1995) Effects of defoliation and antitranspirant treatment on transplant response of scarlett oak, green ash and Turkish hazelnut. Journal of Arboriculture. 21 (1). p33-33. Hipps, N. & Nicoll, F. (1997) Preconditioning Trees to Improve Outplanting Performance. In Claridge, J. (ed.) Research for Amenity Trees No. 6: Arboricultural Practice – Present and Future. UK: HMSO. Kozlowski, T. & Davies, W. (1975) Control of water balance in transplanting trees. Journal of Arboriculture. 1 (1). p1-10. Lee, K. & Kozlowski, T. (1974) Effects of silicone antitranspirant on woody plants. Plant and Soil. 40 (3). p493-510. Neumann, P. (1974) Senescence of attached bean leaves accelerated by sprays of silicone oil antitranspirants. Plant Physiology. 53 (4). p638-640. Ranney, T., Bassuk, N., & Whitlow, T. (1989) Effect of Transplanting Practices on Growth and Water Relations of’ ‘Colt’ Cherry Trees During Reestablishment. Journal of Environmental Horticulture. 7 (1). p41-45. Steinberg, S., McFarland, M., & Worthington, J. (1990) Antitranspirant reduces water use by peach trees following harvest. Journal of the American Society for Horticultural Science. 115 (1). p20-24. Watson, G. & Himelick, E. (1997) Principles and Practice of Planting Trees and Shrubs. USA: International Society of Arboriculture. Watson, G. & Himelick, E. (2013) The Practical Science of Planting Trees. USA: International Society of Arboriculture. Wellburn, A., Ogunkanmi, A., Fenton, R., & Mansfield, T. (1974) All-trans-farnesol: a naturally occurring antitranspirant?. Planta. 120 (3). p255-263.

Nope! Didn't know there was one, and a bit of a trek for a meal for me really. See you in July.

Evening all, The ATF conference is now open to booking: Ancient Tree Forum summer conference in Dorset Ancient Tree Forum Hope to see some of you there!

26/02/16. Fact #161. In the urban environment, conflict below the ground exists between tree roots and services – namely, sewer pipes. Because tree roots will grow up a moisture gradient, and pipes both contain moisture within and may collect condensation on the outer surface, tree roots are drawn to the pipes and, in many cases, are able to intrude into the pipe network (through small openings; usually at junctions, and when the pipes are old and made of clay). Such intrusion obviously causes issues, with regards to the blockage of the pipes, and their subsequent fixing. In response to this, the aim of the authors in this study was to assess what urban tree and shrub species’ roots were found within pipes, whether different species and cultivars had different rates at which their roots were able to enter into the pipes, and if the material the pipe was made of impacted upon the rate of root intrusion. A CCTV image of tree roots blocking a pipe entirely. Source: South Gippsland Water. Underground sewage pipes were (prior to the study, from 1970-2007) inspected – via CCTV cameras – in the Swedish cities of Malmö and Skövde, and the number of root intrusions along pipe lengths were established and mapped as a result (a total of 2,180 intrusions along 33.7km of pipe). From these records, the authors located survey sites. These surveys also noted what the pipe was made of (concrete or PVC), the pipe’s date of construction, and the pipe dimensions. In relation to the plants featured in the study, a 2008 survey of the tree and shrub populations in both cities led to 4,107 individuals being identified within a 20m radius from the pipes where intrusions had been located. Data from earlier inventories enabled the authors to expand the research to 14,552 trees and shrubs. Once the tree and shrub locations had been plotted against locations of root intrusions into pipes, the trees were segmented into 186 different genera, species, and cultivars. As this was considered a vast range, the authors sought to narrow-down the list to a more manageable number. This was achieved by selecting only those trees and shrubs within 10m of an intrusion point, where no other vegetation was found within the original 20m distance; though if two individuals of the same species were found within a 20m distance from an intrusion point then the nearest tree of the two would feature as part of the survey. After the final tree and shrub list (comprising of 2,4,21 individuals from 52 different species and cultivars) was drawn up and the data relating to pipe intrusions analysed, it was found that roots of both broadleaved and coniferous species were able to intrude into pipes. Curiously, it was the PVC pipes (0.661) that had a greater rate of intrusion than concrete ones (0.080) per joint (one length in between two joins). The below table outlines species included within the study, and the rate of root intrusion. Evidently, there are many tree species featured, and this was after many had already been filtered-out of the study scope. Data captured within the survey for each tree species (or genus) relating to the rate at which roots intruded into pipes. From the results gathered, the authors remark that the rate at which Malus floribunda entered into pipes was very significant. Compared to previous studies, and even compared to other species of Malus, this species could be considered very able in terms of root intrusion. In fact, so great was its ability to enter into pipes that it trumped willows at a rate of 3:1. At a broader level however, what this study shows is that many tree and shrub species have similar rates of intrusion into sewer pipes, which therefore suggests that discrimination against particular species may not necessarily be wholly justified. Building on the above comment, we can observe that Tilia cordata and some species of Ulmus also intrude into pipes quite significantly, and even more so than the Salix species observed during the study. Not surprisingly however, Populus canadensis was found to have roots within pipes more often than most other species surveyed (asides from Malus floribunda). Granted, other Populus species were almost half as likely to enter pipes, in light of this survey data. Therefore, it’s not simply a case of observing particular genera that infiltrate regularly into pipes, but particular species within a genus. This seems constant throughout, though Acer spp., Malus spp., Populus spp., and Ulmus spp. most effectively demonstrate this. Interestingly, the lower than expected rate of root intrusion by Populus spp. and Salix spp., the authors allege, is because previous studies have obtained results with a disproportionately high number of thse two genera across the survey sites. As a result, it may simply have been a case that, because these two genera featured so heavily, their roots were more often found in pipes than other genera and species were. If populations of each tree species were normalised, it may have been found that other tree genera and species intruded into pipes more frequently, potentially. This is, in fact, what this study shows, as it was the mean number of root intrusions per pipe joint that were calculated (instead of just the number of intrusions). Granted, this study was not without its limitations. The authors even acknowledge this, and state that tree and shrub species present on a site is not the only determining factor to do with intrusion rate. Soil properties, what pipes are made out of, their age, condition, and the distance to the nearest pipe from a tree are also almost certainly to influence upon infiltration rate. This study is nonetheless serious food for thought, and consideration should of course be given as to what species are to be planted in areas near to pipes. Hopefully, this research will aid with the decision-making process (or, perhaps, the opposite!). Source: Östberg, J., Martinsson, M., Stål, Ö., & Fransson, A. (2012) Risk of root intrusion by tree and shrub species into sewer pipes in Swedish urban areas. Urban Forestry & Urban Greening. 11 (1). p65-71.

25/02/16. Fact #160. Colonisation via active pathogenesis involves direct penetration of the host by the fungal pathogen, largely through the roots though also via air. The establishment of sufficient inoculum base (such as a dead stump or infected root) is critical for successful active pathogenesis, given the aggressive nature of active pathogenesis (Boddy & Rayner, 1983; Lonsdale, 1999; Schwarze et al., 2000; Shigo, 1986). Fungal species of this strategy can employ tactics that infect both healthy individuals and stressed individuals, depending both upon the species of fungus and the context of the site. Active pathogenesis can be broken down into three categories: ectotrophic root infection, wound infection, and canker production (Boddy, 2001). Establishment is via the production of pectinolytic enzymes that destroy pit membranes and advance the spread of desiccated zones, or through wholly combative behaviour where parenchyma cells are destroyed completely during – or more likely in advance of – colonisation. The latter is achieved by the creation of superficial, predominantly non-assimilative mycelium (such as soil rhizomorphs with Armillaria spp.) that grows over the surface of roots, inducing dysfunction and cell death. In killing such cambial tissues, the fungi can colonise without significant hindrance (Garrett, 1970; Rayner, 1993; Rayner & Boddy, 1988). Such strategists may also utilise pre-existing stress within the tree, caused for instance by defoliating insects or pathogenic disease, as a means of entry as a secondary pathogen. As energy must be used by the tree to combat the damage induced by such damaging agents, there is less energy available for additional defensive processes beyond that of combating the damaging agent. Active pathogenesis strategists can utilise this situation to their advantage, as it may mean that (when focussing on the rooting system of a tree) the boundaries between woody and non-woody roots do form form root periderms, become ‘corky’, or become suberised, leading to soil-borne fungal pathogens (such as Armillaria spp.) beginning their attack (Shigo, 1986). In some cases, such secondary infections can be so rapid that they are mis-identified as the primary causal agent. An English oak (Quercus robur) that has been aggressively colonised (on all sides) by Armillaria mellea. The well-known pathogens Heterobasidion annosum and (as ascertained) Armillaria mellea are classified as active pathogens, with colonisation of the sapwood being preceded by mycelial development in the bark. This leads directly to the death of the cambium within the region, and enables subsequent colonisation (Boddy & Rayner, 1983; Fox, 2000; Lonsdale, 1999; Schwarze et al., 2000). The preceding development in bark is a result of spores being washed into the soil, via rhizomorphs, or by direct contact with roots of a separate but infected host (Wargo & Shaw, 1985). Interestingly, Armillaria spp. will by-and-large colonise via soil rhizomorphs. This may be because the spores of the genus are suspected to have to pass through the guts of insects associated with the fungus, before they can successfully germinate (Shigo, 1986). Therefore, much like tree seeds, fungal spores may have an ‘activation’ process equivalent to stratification, fire, digestion, or otherwise – if the means of activation is not present, then the spores will not germinate. As briefly touched upon above, infection can (perhaps only rarely) occur in branches when, under humid conditions, the fungus produces highly water-resistant bridges between branches that come within close proximity to one another. In the UK the fungus Hymenochaete corrugata, which is considered largely a specialised opportunist of Corylus avellana, establishes within the canopy and then spreads further by bridging from colonised canopy space to healthy branches of different hazel specimens (Ainsworth & Rayner, 1990). Fungi that employ active pathogenesis as a means of colonisation may also rely initially upon the aforementioned colonisation strategies (heart rot, specialised opportunism, and unspecialised opportunism) in order to establish an inoculum base from which they can invade healthy sapwood. Stereum gausapatum is an example of this upon Quercus spp., where it is considered to exercise all four strategies to varying extents (Rayner, 1993). References Ainsworth, A., & Rayner, A. D. (1990) Aerial mycelial transfer by Hymenochaete corrugata between stems of hazel and other trees. Mycological Research. 94 (2). p263-266. Boddy, L. & Rayner, A.. (1983) Origins of decay in living deciduous trees: the role of moisture content and a re-appraisal of the expanded concept of tree decay. New Phytologist. 94 (4). p623-641. Fox, R. (ed.) (2000) Armillaria Root Rot: Biology and Control of Honey Fungus. UK: Intercept. Garrett, S. (1970) Pathogenic Root-Infecting Fungi. USA: Cambridge University Press. Lonsdale, D. (1999) Principles of Tree Hazard Assessment and Management (Research for Amenity Trees 7). London: HMSO. Rayner, A. (1993) New avenues for understanding processes of tree decay. Arboricultural Journal. 17 (2). p171-189. Rayner, A. & Boddy, L. (1988) Fungal Decomposition of Wood: It’s Ecology and Biology. UK: John Wiley & Sons. Schwarze, F., Engels, J., & Mattheck, C. (2000) Fungal Strategies of Wood Decay in Trees. UK: Springer. Shigo, A. (1986) A New Tree Biology. USA: Shigo and Trees Associates. Wargo, P. & Shaw, C. (1985) Armillaria root rot: the puzzle is being solved. Plant Disease. 69 (10). 826-832.

24/02/16. Fact #159. I thought I'd write more about this. I touched upon it in an earlier fact, though read it again and have wrote about it all in more detail. Awesome paper! It goes without saying that the world of mycorrhizal fungi is so vast and complex that we’re only just beginning to scratch away at the surface of understanding, though this doesn’t mean we haven’t made some very interesting developments over recent decades. For example, we know that trees may use mycorrhizal networks to ‘trade’ resources across a single species and across differing species, as do we know that they will ‘communicate’ to signal neighbours about upcoming defoliation events by insects. However, whilst we understand the concept, we aren’t necessarily in possession of an arsenal of data that can really begin to demonstrate the intricacies of mycorrhizal networks. I feel that this study is one that begins to establish knowledge of such intricacies, and therefore I hope that you find this as brilliant and mind-boggling as I did when I first read it a few months back (and also hopoe I am making sense with what I write!). The focus of this study was a group of 67 Douglas fir (Pseudotsuga menziesii) of varying ages (courtesy of natural regeneration) in an area of 30m x 30m, and on the manner in which the ectomycorrhizal network of the species Rhizopogon vesiculosus and Rhizopogon vinicolor impacted upon the connectedness of Douglas fir individuals. By a similar token, it looked at the population structure of the two fungal species, across the study site. In order to obtain data required to draw conclusions from the study aims, samples of soil were taken from four sides of each tree within the plot area (usually within the drip line, though if canopy cover was lacking then obviously not so). This enabled for the authors to theoretically obtain fibrous tree roots from each individual, and analyse the tree roots not only to identify the Douglas fir they were from, but to determine whether the two Rhizopogon species were present within both the root cambium and soil environment and, if so, of what genet they were from. The map below shows the plot area, and the sample locations. From each sample location, arrows are drawn to show what tree’s roots were found at each sample site, and from what Rhizopogon species (and genet) the roots were associated with. If we take, for instance, the upper-most blue-shaded area indicating a Rhizopogon vesiculosus genet, we can see how the genet is connected to many different trees across the site. These trees were thus deemed to be ‘connected’, as they shared an ectomycorrhizal network. R. vesiculosus genets can be seen in the blue-shaded areas, and R. vinicolor genets in pink-shaded areas. The coloured lines around the shaded areas represent different genets of the two species, and the black dots within are the sample sites. The lines from the black dots show the links to the Douglas firs, which can be seen as the green star-like shapes (larger ones signify larger trees, and there are a total of four ‘cohorts’ marked by different-sized shapes). The arrow marks the Douglas fir most connected to other trees. In light of the results obtained, which are shown above (visually), the authors identified a total of 56 Douglas firs that were connected with other trees in (largely) the plot area, via the ectomycorrhizal networks created by the two Rhizopogon species (and one fungal genet connected 19 trees!). 45 of the trees were inside the plot area, though a further 11 were outside (and this is why some are plotted outside the sample area). Within the site, 27 ectomycorrhizal genets were also found, of which 14 were from R. vesiculosus and 13 were from R. visicolor. 18 of the genets, 9 from each species, were found to connect at least two trees together. More associations were more frequently found amongst the larger and older individuals, most probably because they had been there longer and their larger rooting environments enabled them to assume more associations with ecotmycorrhizal genets. The table below provides a more detailed breakdown of the genets found and their associated with the different cohorts of Douglas fir. A table showing the data obtained from the study. In terms of the population structure of the mycorrhizae and its impact upon the Douglas firs, the authors found that two trees over 43m apart shared a connection via only two different ectomycorrhizal genets. Their connectedness had to span over more than one genet, as the maximum distance one genet (R. vesiculosus) spanned was around 20m. The ability of R. vesiculosus to span greater spatial distances may also be the reason behind why it was found to connect (10.2), on average, more trees per genet than R. vinicolor (4.4). The most connected tree (at 94 years of age), marked with the arrow in the first image, was considered to be ‘central’ to the overall ectomycorrhizal network, and had a relationship with 11 different ectomycorrhizal genets and 47 other Douglas fir. A total of 62% of the Douglas fir from Cohort 1 and Cohort 2 were also found to be connected with trees from Cohort 3 and Cohort 4. This means that these younger specimens shared associations with the same fungal genets that older specimens were connected to, which the authors found interesting as it suggested that the fungal species surveyed had Douglas fir hosts that would ensure longevity of its existence within the landscape (as if the fungus has anticipated that, by only colonising older specimens, it could itself cease to exist when its old hosts all die out – succession-planning, if you will). Furthermore, it enables the younger specimens to share an already established inoculum base, from which carbon and water can be provided by the older specimens to aid with establishment. Beneath, a further image shows associations between individual Douglas fir studied during the research. Showing how individual Douglas fir were linked to other individuals, the coloured circles vary in size depending upon tree DBH and colour (from yellow [young] up to dark green [old]) depending upon age. Thicker lines between individuals shows a greater degree ot connection, associated with how many different ectomycorrhizal genets linked them. What we need to be aware of here is that this study was done over a tiny fragment of Douglas fir forest, and therefore if the associations were extrapolated out over an entire landscape, the connected nature of individuals to others would be absolutely incredible. Not only this, but because two trees were found to be connected at over 40m away, it highlights how the above-ground isolation of individuals in a stand masks the intricately-connected nature of the individuals beneath. Thus, we must really see a forest as a network, in place of individual trees. The fact that older individuals were found to have many more connections, on average, than younger ones, also highlights the criticality of retaining older specimens in a stand – if only for the benefit of safeguarding ectomycorrhizal networks that aid with younger specimens obtaining required resources for their growth. However, we must also recognise that the mycelial networks of the two Rhizopogon species studied benefit hugely from the older trees, and retaining them is also of benefit to their existence. Targeted felling of large individuals, therefore, could wreak havoc (and rather quickly) upon the entire system, as the stand’s resilience is built upon these (and related) ectomycorrhizal networks that have established and persisted for a long time. Even if, as the authors suggest, a connection does not provide the young tree with resources, it will still benefit from connecting with a well-established ecotmycorrhizal genet that is itself healthy and fully-functioning as a result of obtaining its carbon from upper-canopy, mature Douglas fir. It does not pay to be isolated from the crowd. Source: Beiler, K., Durall, D., Simard, S., Maxwell, S., & Kretzer, A. (2010) Architecture of the wood‐wide web: Rhizopogon spp. genets link multiple Douglas‐fir cohorts. New Phytologist. 185 (2). p543-553.

I personally wouldn't go on an ad hominem, as I think it's always important to entertain different views and opinions, but there are certainly some things I struggle to agree with from an ideological standpoint - one of which is the use of fossil fuels, which it is argued that by sheer virtue of the fact they have done so much 'good' for humanity then they something to justify using (he discusses this in two recent videos with a guest about fossil fuels). However, the videos make me consider my own views, and they certainly broadened my thought horizons.

Here's our two:

Evening all, Been watching so many of this guy's videos lately. Some seriously intelligent discussion across an absurdly wide array of topics. I have my own opinions on his videos, and my views vary as much as his videos vary in terms of topics covered, though there's no doubt it's some hugely stimulating material that is very challenging (in a good way). I don't know whether this will be of interest to anyone here, though by all means check out some of his stuff and see what you think. His most recent one I really enjoyed, and it's actually quite different to much of his other stuff. [ame] [/ame] Channel - https://www.youtube.com/user/stefbot/videos

Can we close this thread? We're reminiscing over something that has been and gone, without trying to sound insensitive. Discussing it is not constructive by and stretch of the imagination.

24/02/16. Fact #158. This strategy sees fungi colonise the sapwood in a living tree by taking advantage of the tree’s physiological stress due, for example, to root dysfunction or drought conditions (Boddy, 2001; Parfitt et al., 2010; Rayner, 1993; Rayner & Boddy, 1988; Schwarze, 2008). Development will be in apparently intact, yet dysfunctional sapwood of areas of the tree which remain uninjured, though decay onset will be timed with desirable conditions within the tree (induced by stress). Single genotypes will usually manifest with distinct speed (up to a few metres per year), and spread extensively, using the xylem as a vector, throughout underlying sections of bark, forming vast decay columns. This therefore entails that such decay fungi are present extensively within the tree (yet not in an overt manner) within its functional sapwood, prior to attack. Onset of decay is likely not observed until the tree suffers localised xylem dysfunction, given the high water content of functional sapwood is undesirable for fungal decay (Baum et al., 2003; Boddy, 2001). This mature Betula pendula, whilst still alive, has been aggressively colonised by Piptoporus betulinus, following physiological stress. Latent invasion may also in fact result from the development and subsequent assimilation of separate fungal mycelia, under the conditions associated with dysfunction. The spores may have spread widely within the sap stream over long periods, initiating only later (following stress in the host) their mycelial development, with subsequent ‘assimilation’ of the many establishing mycelium networks as they coalesce. The consequent decay associated with the assimilation and the host’s inability to defend against the widespread attack by the host may ultimately be very significant (Boddy & Rayner, 1983; Parfitt et al., 2010). Research also suggests that even once sapwood does become dysfunctional, presence of decay may not become overt. Decay may not even begin whatsoever. Further, as many fungal species latently exist within specific hosts, particular conditions may only trigger the onset of decay by one, or a portion of, the fungal species present (Parfitt et al., 2010). Additionally, such strategists have a high degree of selectivity with regards to their host site and / or species, with branch junctions being a principal location for decay onset (Boddy, 2001; Rayner, 1993). This is perhaps due to the lower side of the branch junction being an inherent weak point within the tree, because the site has low energy reserves – particularly when the branch attached to the parent branch or trunk is dying (Shigo, 1986). An example of a specialised opportunist’s strategy is therefore the entering into a dying branch with sapwood dysfunction, likely induced by the inability to compete with its neighbours for light, waiting at the junction of the dying branch until the spores are incorporated into the heartwood via secondary thickening, and then establishing and beginning the attack (Baum et al., 2003; Chapela & Boddy, 1988a; Chapela & Boddy, 1988b; Oses et al., 2008). Such a colonisation trait can be described as endophytic – this is where a species resides within the host with no adverse impact upon the host until conditions are right for attack (Baum et al., 2003). Such a scenario may even be beneficial in terms of facilitating the “natural pruning” of limbs that become dysfunctional as tree canopies expand (Rayner, 1993). Under some conditions, certain specialised opportunists may also be able to colonise via active pathogenesis (Rayner, 1993). References Baum, S., Sieber, T., Schwarze, F., & Fink, S. (2003) Latent infections of Fomes fomentarius in the xylem of European beech (Fagus sylvatica). Mycological Progress. 2 (2). p141-148. Boddy, L. (2001) Fungal community ecology and wood decomposition processes in angiosperms: from standing tree to complete decay of coarse woody debris. Ecological Bulletins. 49 (1). p43-56. Boddy, L. & Rayner, A.. (1983) Origins of decay in living deciduous trees: the role of moisture content and a re-appraisal of the expanded concept of tree decay. New Phytologist. 94 (4). p623-641. Chapela, I. & Boddy, L. (1988a) Fungal colonization of attached beech branches. I. Early stages of development of fungal communities. New Phytologist. 110 (1). p39-45. Chapela, I. & Boddy, L. (1988b) Fungal colonization of attached beech branches. II. Spatial and temporal organisation of communities arising from latent invaders in bark and functional sapwood, under different moisture regimes. New Phytologist. 110 (1). p45-57. Oses, R., Valenzuela, S., Freer, J., Sanfuentes, E., & Rodriguez, J. (2008) Fungal endophytes in xylem of healthy Chilean trees and their possible role in early wood decay. Fungal Diversity. 33 (1). p77-86. Parfitt, D., Hunt, J., Dockrell, D., Rogers, H., & Boddy, L. (2010) Do all trees carry the seeds of their own destruction? PCR reveals numerous wood decay fungi latently present in sapwood of a wide range of angiosperm trees. Fungal Ecology. 3 (4). p338-346. Rayner, A. (1993) New avenues for understanding processes of tree decay. Arboricultural Journal. 17 (2). p171-189. Rayner, A. & Boddy, L. (1988) Fungal Decomposition of Wood: It’s Ecology and Biology. UK: John Wiley & Sons. Schwarze, F. (2008) Diagnosis and Prognosis of the Development of Wood Decay in Urban Trees. Australia: ENSPEC. Shigo, A. (1986) A New Tree Biology. USA: Shigo and Trees Associates.

Cracking shots, there! Liking the Kretz, though that stack of Gano is really quite sublime. Made a mental note to look for these species, or evidence of, as well.

Is there a report calculating the potential impacts of construction on the tree, and subsequent pollution? The road is going with 15mts, though will heavy goods vehicles be closer by, and how will the oak be protected (and will builders actually obey the regs and not jump inside the fence)? Pardon the cynicism.