Kveldssanger

I went through the whole range of emotions watching that video, I will admit!

In light of what you said there Jon, I completely agree (and am glad you said that). I suppose the manner in which I have tended to understand 'precedent' is that, whilst not 'binding', it's something that holds influence over future decisions. I recall there was a more recent case that was originally quite 'way-off' from the precedent, and at the court of appeal the judges overturned it and ruled more with precedent (cannot for the life of me remember the case, right now - someone please jog my memory!), so from that I kind of took it as something that means that a 'passive' and perhaps 'partial' continuation of the status quo applies (as in, don't you attempt to deviate wildly from the norm else you'll get proverbially burned). I shall make sure to add to my work something along the lines of what you have said, and that quote you mention is very good! Thanks.

It's merely a case of immersing into something, in my opinion. For example, I cannot fluently speak French if I don't constantly practice the language at every given opportunity (for the record, je ne parle pas Francais). We're all good at different things, and I am in no doubt you're far better at many things than I am. Hopefully my fact of the day thread isn't too confusing, as I do try to make it as easy to read and understand as possible!

Lol! No worries, mate.

Am I missing a joke, or have you replied to the wrong thread?

[ame] [/ame] Hardly been viewed. Enjoy!

I'll +1 this.

...went to mow a meadow.... So I'm looking at case law relating to poisonous trees for my Lvl 4, and I thought of something. It may have very well been discussed before, to death (pun intended), though I want to pick brains of those here one further time. In my report, I have written the following: Building upon this point however, one may raise questions with regards to what occurs if an individual assumed control of a parcel of land on which a yew tree resides adjacent to a boundary. In case law outlined on poisonous trees (specifically Erskine v Adeane [1873] and Cheater v Cater [1914]*), it was ruled that if a tenant assumes control of land where a yew tree already exists along a boundary, then there is no claim if an issue arises as a result of animals grazing upon the foliage, though how would this apply to domestic situations? For instance, if a homeowner rented, from a landlord who owned a row of houses, a property whose back garden was met, in one corner, by a mature yew tree in an adjacent property (owned by the landlord) that partially overhung the boundary, then if their large pet dog then consumed the foliage from that tree, would there be a case to be made against the landlord, in light of the fact that the tenant accepted the property as it stood with the yew tree being there? * from the judge, who quoted in the 1914 case: "in a case of this kind the tenant takes the land demised as it is, and therefore if the tenant here took the land with the yew trees growing over it so that his cattle could eat of the branches and they did eat, he cannot complain". I understand the beast that is common law, and recognise that both overhanging branches (nuisance abatement) and the ruling in Rylands v Fletcher [1868] that included the phrase "it seems but reasonable and just that the neighbour who has brought something on his own property (which was not naturally there), harmless to others so long as it is confined to his own property, but which he knows will be mischievous if it gets on his neighbour's, should be obliged to make good the damage which ensues if he does not succeed in confining it to his own property" also may apply, though I'm curious to know exactly where the precedent would sit with my hypothetical scenario. Hopefully this makes sense - if not, let me know! Cheers.

Indeed! Hopefully of use. Correction to above post: ...species such as Ustulina deusta (syn. K. deusta) and Ganoderma applanatum (the former, exclusively) were found where the tree was in advanced stages of decay...

08/03/16. Fact #169. Trees located within the urban environment are, by default, more of a risk to public and property. This is because beneath many such trees are permanent (or more frequently temporary) target zones, which would not necessarily be found to such a degree in a rural setting. Having said that however, many urban trees have a very low level of risk, and are thus deemed to hold an acceptable level of risk. Granted, some urban trees present more of a risk, and the manifestation of a greater level of risk can occur through a variety of different means. One significant contributing factor to the increaed risk of an urban tree, and which is the focus of this post, is fungal decay. Where trees have been wounded, are stressed, or may even be largely in good condition, fungi can enter into and establish within the structure of a tree, break down the lignin and / or (hemi-)cellulose within the wood, and thereby reduce the tree’s structural integrity. In turn, the associated hazards increase. Therefore, understanding more about fungal decay is important, and the authors of the study discussed below pursue a greater undestanding of fungi in our urban trees. By using some of the trees in Helsinki, Finland, the authors sought to gain more of an understanding about the abundance and patterns of decay of certain common wood-decay fungi found in the city. In total, 194 trees (76 of the genus Tilia, 60 of the genus Acer, and 58 of the genus Betula) in both parks and streets were assessed within the study, of which all were showing signs of health decline, or were outwardly hazardous. During the inspections to determine that such trees were indeed hazardous or in decline, information was gathered in relation to the external symptoms (fungal brackets, cracks, cavities, etc) and their exact locations (including height upon the structure) upon the trees. Subsequently, all were felled over a period of time between 2001-2004, and from there the research began into assessing what fungal species caused the decay (at times, DNA sequencing was needed, and notably for differentiating Ganoderma species from one another), and how extensive horizontal decay was within the tree’s structure (by taking cross-sections around areas of dysfunction). Following on from the investigations post felling, the authors identified 13 fungal species and genera within the host Acer spp., Betula spp., and Tilia spp. Pholiota sp. was most frequently found to have colonised all three tree genera, and often other fungal species were found alongside. Other fungal species, such as Piptoporus betulinus, were only found upon trees of the Betula genus, though of course the host preferences (not all fungi are generalists) of different fungal species will determine, from the limited range of tree species assessed, what fungi could possibly be present on each of the three genera, and how often (Rigidoporus populinus, for example, was predominantly – but not exclusively – found upon Acer spp.). Interestingly, Piptoporus betulinus was also never found alone within its host, which therefore suggests other fungi will also have contributed to decay within the Betula spp. featuring in this study (this may align with its strategy of specialised opportunism, where the fungal spores wait for the host Betula sp. to become stressed before attacking). In fact, the only three fungal species isolated from the trees of this study that occurred alone around 50% of the time were Ganoderma applanatum (syn: G. lipsiense), Hypholoma sp., and Phellinus igniarius. This perhaps suggests they they are either far more competitive and defend their ‘patch’ aggressively, they enter into trees and take advantage of substrate conditions other fungi cannot similarly exploit, or succeed into substrates other fungi had already decayed (and then exited). Below, the table (pardon the small size) outlines all fungal species isolated, and from which hosts. For a better view of this table, please visit the journal article itself (linked at the bottom). Armillaria spp. does not include A. mellea nad A. ostoyae, but instead mainly A. cepistipes and A. borealis (both weak pathogens, which are usually saprophytes). Additionally, only certain fungal species could actually be readily identified by their sporophores (including Rigidoporus populinus and Ganoderma applanatum), because not all fungi had produced sporophores at the time of inspection and felling (and if they did, they may have been few and far between – Hypholomoa sp. never produced fruiting bodies, and no symptoms were externally evident to suggest it was there). However, the authors do note that sporophores were found on the trees where decay was most extensive in the radial direction, and this may indeed make sense when one considers that fungi will not produce a sporophore (an exit strategy) unless there is a need to do so (such as running out, locally, of substrate – indicating wider radial spread in the direction of the sporophore). Not only this, but even where fungal sporophores were not evident, crown dieback could be observed as a result of decay by Piptopirus betulinus and Inonotus obliquus, for example. The table beneath further outlines on how some fungi, whilst present in the tree (either outwardly or via laboratory analysis), did not cause crown symptoms to show. For many fungal species, the crown symptom rate is actually very low. A break-down of how different species of fungi could (or could not) be observed within a tree. In relation to the extent of decay, most trees were either hollow (57%) or were significantly decayed (35%), and particular fungal species were only found in hollowed trees (including Armillaria spp., Phellinus igniarius, and Pholiota spp.). Conversely, species such as Ustulina deusta (syn. K. deusta) and Ganoderma applanatum were found only where the tree was in advanced stages of decay, and variation existed between how frequent their presence was (the latter was more routinely found as a primary decay agent, whereas the former was not found in discoloured wood but only where wood was already very decayed). Of the 8% of trees where wood was only discoloured, Piptoporus betulinus and Ganoderma applanatum were two examples of fungal species that could be found. From this data, one can recognise how different fungi will occupy different stages of the decay process, and therefore a succession of sorts may perhaps occur amongst individual species. Building upon the above, the authors also recognised how different fungal species would create different radial decay patterns (see the below table). Species including Cerrena unicolor and Ganoderma applanatum were observed to more readily create decay cross-sections of greater radial spread, for instance (and also invade the vascular cambium). However, most species were found to extend out to across more than half of the cross-sectional area of a tree’s main stem, which means the critical t/R value of 0.3 (Mattheck’s hollow tree failure theory) is quite significantly encroached upon, and for 5-6 of the fungal species here, surpassed. In terms of the location of decay, it was found that Ganoderma applanatum was usually found in the lowest 1m of the main stem, which means entire tree failure is very possible when decay is very extensive. Other fungal species were found in different locations, including branch forks (Rigidoporus populinus). In such an instance, decay may only induce failure further up the tree’s structure. Comparing different fungal species observed and how far out (radially) they were observed to go, at a cross-section. Looking further at the table above, a few additional observations can be made. Firstly, as even stated by the authors, Pholiota spp. may be pathogenic within the rooting system of a tree, and because this study only assessed the above-ground structure, exact extents of decay within host trees may not have been fully understood. Armillaria spp. is also a root pathogen, and the same comments apply to that genus as well (thought A. mellea and A. ostoyae were not isolated in this study, so Armillaria spp. may be under-represented for severity). However, in general, the table does demonstrate that fungi may very well facilitate failure in the stem or branching area, and particularly for those that extend over the 70% threshold – Ganoderma applanatum may very well cause basal failure, whilst Rigidoporus populinus may cause failure in the lower crown (at a branch junction). In recognising all of this, we can begin to appreciate how fungal strategies (some are notably pathogenic, whilst others are not so) have significant impacts upon how we manage urban trees, and therefore we must understand specific species’ strategies and cater management to meet the ‘needs’ of the tree. There is little use in not discriminating between different fungi, as some (Cerrena unocolor, Ganoderma applanatum, and Inonotus obliquus) certainly have the potential to be more hazardous than others (Pleurotus spp.). Additionally, as some fungal species (Hypholoma spp.) will more typically (or exclusively) succeed into trees already extensively decayed or hollowed (see the below table), recognising their presence may be important for understanding what condition the host may be in. Granted, this is likely common knowledge, though it is still important to recognise this over and over again, as it really is a main crux of tree management for safety reasons in urban areas. It is necessary to note, however, that only three tree genera were studied in this situaton. Therefore, caution should be exercised in forming absolute conclusions, as many urban locations consist of tree species and genera over and above what was assessed in this case. Nonetheless, credit where credit is due – a fantastic study! How different fungal species occupied trees at different levels of decay, indicating how identification of their presence may help detail the condition the tree is in. Source: Terho, M. & Hallaksela, A. (2007) Decay characteristics of hazardous Tilia, Betula, and Acer trees felled by municipal urban tree managers in the Helsinki City Area. Forest Pathology. 37. p420-432.

Nice shots there of a Fomes (and the rest, too). Interested also (seriously). Going with the missus to the Redwood Forests next year (most probably), though also keen to go over to Poland.

Really good study, that! Right up my street, with its implications for conservation. If you read any of this thread, read the one above!

07/03/16. Fact #168. Unless the substrate on which a seed resides is preferable, the germination and successful recruitment of the seedling will likely fail. Compiled with the fact that different species’ seeds require different substrates and conditions to germinate and establish, recognising exactly what constitutes preferable is important. For smaller-sized seeds (such as birch), which will lack nutrients that are internally available with larger seeds (such as acorns), it is typically accepted that a more nutrient-rich and external substrate is necessary. Whilst this nutrient-rich substrate may very well be the soil itself, it may even more often not be the soil but decaying deadwood that, courtesy of decomposers (bacteria, fungi, insects), has had its locked-away nutrient mineralised (made freely available for uptake by other organisms). In this sense, for smaller-sized seeds, a change in seedbed (substrate) and microsite conditions may very likely signal a change in the rate at which such seeds germinate. The focus of this post is a study that invesitgated how different seedbed conditions impacted upon the rate of seedling recruitment, performance, and morphology of Betula alleghaniensis (yellow birch). The study was undertaken in 2010 within Quebec, Canada, which is part of the species’ native range, and the seedbeds were all located in forest stands dominated by Acer saccharum (sugar maple). As a general rule of thumb, yellow birch prefers nutrient-rich substrates (notably decaying deadwood, though also soil) that have good light availability and are largely leaf litter-free; the same can most probably be said for many other species of the genus Betula, too. Therefore, the main aim of the study was to ascertain whether there was a difference in suitability between these preferable substrates available in such an area of the species’ native range. Within the overall study location, four areas were selected. All had ‘recently’ been harvested with a selective cutting method, with two areas having been cut in 2004 (new cut) and another two having been cut in 1994 and 1995 (old cut). Sugar maple was the most dominant tree species on all sites, with yellow birch also featuring prominently. Other tree species were present, including (but not exclusively) Acer rubrum (red maple), American beech (Fagus grandiflora), and Thuja occidentalis (eastern white cedar). In each area, yellow birch presence (a total of 1,015 individuals) within the understorey was measured, and all that ranged from 15-330cm in height were recorded. Where each yellow birch was recorded, the seedbed (mineral soils, mosses, deadwood, moss-covered deadwood) and microsite types (pits, stumps, fallen trunks, etc) were also noted, as was the level of canopy ‘openness’. Where a seedling was found upon deadwood, the level of decay (from 1-5) was also recorded, as was from what species the deadwood came. To ascertain performance and morphology, a total of 274 of the yellow birch were also removed from the site, and assessed for their growth increment, their number of branches, and their age. These individuals were also dissected into their roots, stem, branches, and leaves, and each part was weighed after being dried to measure dry-weight biomass. Roots were also measured and segmented into categories associated with their diameter. A view of the understorey of a stand of predominantly sugar maple and yellow birch in Quebec, Canada. Source: Wikimedia Commons. Explanations relating to the methodology now over, we can begin to assess the results. Firstly, it was found that seedbed and microsite types were different between the old and newly cut stands. From this, we can perhaps recognise that harvesting of a site can have an effect upon recruitment of yellow birch seedlings. Looking more into this this difference, the authors found that moss-covered deadwood was the principal substrate upon which yellow birch seedling would grow (46% and 29% of all seedlings in old and newly-cut stands, respectively), though mineral soils would support more seedlings in newly-cut stands (at 41% of all seedlings found, compared to 34% in older cuts) – probably because of less deadwood being available. Curiously, deadwood lacking moss was less often used as a substrate, with only around 20% of seedlings in each stand type growing upon it (below, the upper graph demonstrates these differences). In terms of what microsite was preferred, skid trails were most frequently found to accomodate seedlings in newly-cut stands, and in older stands skid trails were second-best to stumps (below, the lower graph demonstrates microsite differences). However, across both site types, skid trails supported almost equal amounts of seedlings (of which most grew directly within the soil), as did trunks. Perhaps, the suitability of skid trails is clear, as they may very well generally have higher light levels reaching the forest undercanopy. How the seedbed type (DW – deadwood; MDW – moss-covered deadwood; MS – mineral soil) impacted upon seedling recruitment of yellow birch in newly-cut stands, and those cut some time ago in 1994 and 1995. How different microsite types supported different amounts of yellow birch (PM – pits and mounds; S – stump; ST – skid trail; T – trunk; WD – woody debris). In terms of the age distribution of seedlings across both stands, seedlings in the stands cut in 1994 and 1995 (15-16 years prior to the study) were, on average, 12.6 years old, and for newly-cut stands (cut six years prior to the study) they were 9 years old on average. This in itself is interesting, as it suggests some of the seedlings in the newly-cut stands pre-existed the change in site conditions when harvesting took place (though, of course, where seedlings were found in skid trails they surely could not have pre-existed harvesting). As for the average height of seedlings and how open the canopy was above their location, no marked differences were found between both stand types, though mineral soil did support seedlings of greater height (on average) when compared to deadwood and moss-covered deadwood. Focussing on those individuals found on deadwood, over 60% were found growing on conifer logs. Because the dominant species in the forest stands were not conifers, this suggests that coniferous species occupying a smaller total population of no more than 20% of the total amount of trees (including eastern white cedar) more markedly supported the regeneration of a species dominant in the stand (yellow birch). This alone is important for forest managers and conservationists. The inverse was actually found with sugar maple, where its deadwood only supported around 10% of all seedlings – this is in spite of it occupying 50% of total the total number of individuals in the stand. Away from the species of deadwood, more heavily-decayed deadwood was found to support more yellow birch seedlings (see below graph). How different decay classes of deadwood (1 being the lowest) supported different numbers of yellow birch seedlings. Looking at morphological traits of the seedlings, it was found that those seedlings growing within the soil had the greatest growth increments. However, those growing upon deadwood (both covered and not covered in moss) had a higher fine mass root ratio, meaning that their root systems were more developed than those growing in mineral soil of an identical height. Not only this, but leaf area ratio (total leaf area compared to overall seedling dry mass) was highest in seedlings growing on moss-covered deadwood. This suggests that, whilst height growth is reduced, the seedlings have better root systems and more leaf area (aiding in resource uptake and photosythesis, respectively), and may therefore be in a better ‘condition’. After all, height is not the only determinant in the quality of a seedling. From these results, what can we conclude? Principally, the benefits of heavily-decayed deadwood cannot go ignored. Evidently, deadwood, and particularly moss-covered deadwood (which will typically be more decayed, anyway – higher moisture levels), is critical for the recruitment of yellow birch, and even in spite of it occupying only small to moderate levels of the forest floor. This is likely because decayed deadwood is more readily penetrable by roots, has more nutrients available for uptake, reduced competitin for resources with other plants, and retains higher levels of moisture which seedlings require. In this sense, much akin to how the less plentiful coniferous deadwood is more important for yellow birch recruitment than broadleaved deciduous deadwood (probably because coniferous deadwood decays more slowly, thereby providing a viable substrate for a longer period of time, which enables a seedling to develop a better rooting system and anchor into the mineral soils beneath), deadwood is more important than the more spatially abundant mineral soils. This clearly demonstrates how more ‘niche’ substrates need to be conserved in forest ecosystems, in an attempot to retain ecological integrity. Just because something is found in the greatest abundance does not mean it is the most important thing for the ecosystem – perhaps, even the opposite! Here, a yellow birch seedling that started its life growing on the now heavily-decayed stump, has developed ‘stilts’ from where the roots anchored into the mineral soil beneath and the stump then rotted away. Source: Dr John’s Blog. In terms of whether harvesting impacts upon seedling recruitment – yes, and no. Of course, the presence of seedlings growing upon stumps was notable (particularly in older stands, where stumps were of course likely to be more significantly decayed), and such stumps would not exist to any marked degree if harvesting operations did not occur. Granted, one must recognise that stumps may have been more routinely used as a substrate because trunks were likely less available, and therefore seedlings may only be using what is available to them. That aside, the authors comment that yellow birch may be less reliant upon harvesting to free-up the canopy and allow more light to penetrate through, and instead grow successfully and retain a constant seedling cohort if suitable substrates and microsites persist (largely, deadwood that is well-decayed – canopy openness seems not to be highly significant). This is because many seedlings in the newly-harvested stands pre-existed the harvesting date (asides from those growing in skid trails, directly within the soil), suggesting it wasn’t the harvest operations that most actively facilitated seedling recruitment levels. Therefore, the benefits of (well-decayed) deadwood are yet further accentuated. As if there wasn’t already enough justification to retain deadwood, we can now add this study to the ever-expanding arsenal that is amassing at the gates of the forest manager. Without such deadwood accumulation (and notably of coniferous species), the recruitment and performance of yellow birch seedlings may begin to suffer. In time, the entire composition of the forest may begin to alter, if such a suitable substrate becomes lacking. Without doubt, one must allow for a stand to succeed at all times, though there is also a need to conserve and manage with responsibility. For yellow birch, reducing the presence of coniferous species within the stand and not allowing deadwood to accumulate and decay in situ would be an ecological travesty. Source: Lambert, J., Ameztegui, A., Delagrange, S., & Messier, C. (2015) Birch and conifer deadwood favour early establishment and shade tolerance in yellow birch juveniles growing in sugar maple dominated stands. Canadian Journal of Forest Research. 46 (1). p114-121.

I thought only dentists offered such a service?

05/03/15. Fact #167. From the popularity that was associated with my post on wind-related tree deaths in the USA, I thought I’d build slightly on how wind can create hazards by going over a really interesting article in the book Tree Structure and Mechanics Conference Proceedings: How Trees Stand Up and Fall Down. The article looks at how, over the period of 1992 to 1999 in Rochester, New York, wind gust speed impacted upon the rate of street tree branch failures. Because data relating to such failures was held electronically, and old climatic data is ‘easily’ obtainable, the methodology was very simple and solely involved relating branch failure date to the wind speed in that area at the same time. The study is also not lengthy and was in fact created on the back of this study, but the data contained within is absolutely brilliant and so it’ll certainly be of interest to many reading this. As a means of setting the scene so to speak, the authors first establish two things: (1) when branches failed, and (2) when wind gusts were deemed significant (in this case, over 40mph for over 5 seconds). In relation to the first point (see the below graph), it was found that branch failures were most frequent during the months when foliage was present upon the trees (May to October / November) – specifically, July, August and September (even including the 243 failures in strong winds in September 1998) had a very high number of branch failures in comparison to other months. In a way, this is to be expected, as full leaf crowns will drastically increase wind resistance of a crown. Branches will therefore be loaded not only by greater weight from the leaves they are supporting, but the leaves they are supporting will have a large surface area that can readily catch in the wind (which will further increase the loading upon the branch, pushing it closer – or beyond – it’s safety factor). Furthermore, if it’s raining, then the water caught by the leaves will yet further increase the weight the branch will bear. The number of branch failures, per month, in Rochester. Note that 243 failures occurred during September 1998, as a result of strong winds. However, when looking at when the strongest wind gusts were, we can observe something peculiar – the frequency of such gusts is almost an inverse of the rate of branch failures across the calendar months (see below). This suggests that it is not the frequency of strong wind gusts that correlates with branch failure, but simply the occurrence of such a wind gust. The number of wind gusts of 5 seconds or greater, and how strong such gusts were (see legend key). From here, the authors then look to segment the total number of branch failures into categories relating to wind speed. As somewhat expected, there is an exponential increase that begins at around 40mph, and drastically starts to rise at 60mph. The lack of 70-79mph data is because no such gusts occurred during the survey period. The data is shown below. The number of branches failures in Rochester’s street tree population, and at what wind speed the branches were overloaded at. Pulling apart this data further, the authors sought to compare at what wind speeds branches failed at, during both the period in which foliage was present, and when foliage was not present. Results for the branch failures when foliage was present (shown below) are interesting, in the sense that it appears to be that wind gusts alone are not the cause of failure (as noted by the high spike of branch failures at 43mph). Of course, there is marked correlation between wind gust speed and branch failure rate. The authors in fact suggest that the effect of the observed wind gusts on branches may be exacerbated by simultaneous (or prior) precipitation, drought (where wood rays become very dry), and previous stronger and more sustained gusts. Therefore, calmer winds in ‘right’ conditions may at times more readily cause branch failure than when stronger wind gusts occur and such aforementioned influencing conditions are not evident. Branch failure frequency during the time when foliage was still present upon the tree, in relation to the wind gusts that caused such failure. Diverting attention to the leafless period, there seems to be little correlation between branch failure and wind gust speed (as shown below). Perhaps, other climatic faactors (snow, ice, etc), in conjunction with wind loading, will induce failure in such instances; and in times where snowfall or ice accumulation is significant, branches may certainly fail under such extreme loads. Gusts that induced branch failure during the leafless period. So what can we gain from this study? Hopefully, a lot. Admittedly, the sample size was limited (only eight years and in one city), though it goes to show how, at least for broadleaved trees, wind gusts during the summer will indeed be more likely to cause structural failure. Without question, we must not ignore other loading factors that may combine with wind, during the growing season (most probably precipitation). During the winter (leafless period), it seems wind gusts alone are far less likely to correlate to any degree with branch failures, and instead wind gusts may be significantly aided, through the presence of snow or ice, if branch failure does occur. Failure may even occur independently of wind gusts. Source: Luley, C., Pleninger, A., & Sisinni, S. (2002) The effect of wind gusts on branch failures in the city of Rochester, New York, U.S. In Smiley, E. & Coder, K. (eds.). Tree Structure and Mechanics Conference Proceedings: How Trees Stand Up and Fall Down. USA: International Society of Arboriculture.

A good bit by Jeremy Barrell here on ivy (see p7).

I get it all the time as well, even when the ivy is only just starting to climb up the lower stem! I don't understand how the myth has become so widespread, as rarely do I see a tree that is wholly struggling as a result of ivy colonisation (apart from a few hawthorns and the odd oak). In theory, ivy is part of the senescence process of a tree, as over its lifetime its vigour will reduce and ivy will have a greater likelihood of establishing significantly. In time, the ivy may finish the tree off, though not before it has (almost certainly) been declining prior to that (and perhaps for a long period of time). I would agree that the only times to remove ivy would be to reduce wind sail on exposed urban trees, and to safeguard specimen trees from the adverse structural impacts of ivy (altering crown structure, etc).

Disgustingly shameless bump for those that are interested and may have missed this.

Shame it won't ever get reprinted, as it's a classic that, even though Mattheck has put out more books since, is still highly regarded and a seminal text. Got it from a library for a week, and I'd buy it if it wasn't so costly. Until then, my photos of the book will do.

04/03/16. Fact #166. Ivy (Hedera helix), which is classed as a woody liana, can be both good or bad for a tree, depending upon the setting. For example, in urban locations where trees exist as solitary specimens for largely amenity purposes then ivy may be an issue, because its presence increases the wind sail of a tree and also detracts from its amenity value (one cannot appreciate the tree’s structure so readily). Conversely, in a setting where a tree is retained for ecological value, or it simply sits amongst a group (copse, woodland, or forest) of trees, then ivy may be hugely beneficial. The love that ivy receives is therefore relative. This pine (Pinus sp.) was so laden with ivy in its crown that it got blown over in the wind. Looking beyond the mere pros and cons of ivy however, what drives its colonisation? Does ivy discriminate between trees as to which it will ascend and thus colonise extensively (in time), or does it simply colonise whatever host it has in its immediate grasp? In a recent study from 2013 undertaken in the Siro Negri forest in Italy, such questions are answered. Before looking at the results from the study however, it is important to understand a bit more about the Siro Negri forest. Located in northern Italy, it is a small remnant (9ha) of alluvial forest once more abundant across the landscape. A habitat considered ideal for ivy (climatically), tree species include field maple (Acer campestre), hornbeam (Carpinus betulus), hawthorn (Crataegus monogyna), white poplar (Populus alba), black poplar (Populus nigra), oak (Quercus robur), false acacia (Robinia pseudoacacia), and elm (Ulmus minor). Many trees are over 100 years of age, and there has been no significant disturbance since 1970. Back to the study, the authors first identified four plots of 250-320 square metres in 2005 and 2009, and within these plots measured the DBH all trees. Those with a DBH of over 7.5cm were tagged. In 2011 (I don’t know why there was such a wait), the authors returned and undertook an assessment of all ivy stems growing upon the tagged trees that had a DBH of greater than 0.5cm. For all tagged trees, they were assigned one of five categories relating to the colonisation extent of ivy upon their structure: (0) ivy not present / below 1.3m on the trunk; (1) ivy present upon lower half of trunk; (2) ivy extending up into second half of trunk but not yet into the crown; (3) ivy within lower crown’s principal branching structure, and (4) ivy across entire crown. In terms of further data gathered, on top of the DBH measurements undertaken in 2005-2009, radial cores at a 50cm height were taken from each tree to estimate age in 2011. If age was not evident as ring growth was asymmetrical or decay was present, the core was discarded. Similarly, radial cores from 50 randomly-selected ivy stems (43 once some were discarded) were taken at a 50cm height, again in 2011. The number of ivy stems present on each tree was also measured. Moving on to the all-important results, the authors found that there were a greater number of ivy stems of 0.5cm-1cm in diameter than there were of diameter between 1cm-2.5cm, and 2.5cm+ (657, 345, and 225 stems, respectively). 52% of tree surveyed were host to more than one ivy stem, though only 17% of trees had ivy growing throughout their crown (category 4).The ivy stem of most significant size was 14cm in diameter, and had 53 growth rings. However, an older ivy stem of 69 years was found, albeit with a stem diameter of just 9.5cm. In addition to this, not only was it was found that areas where tree density was lower and trunk diameter was greater that ivy stems greater than 0.5cm were more abundant, but that tree age was also associated with increased ivy colonisation (which is expected, considering older age usually means a greater trunk diameter and, at least in woodlands, lower tree density per hectare). Therefore, isolated oaks (Querus robur) of more significant age and size were observed to be host to a greater abundance of ivy stems and overall extent of ivy than the smaller and denser field maples (Acer campestre) and hawthorns (Crataegus monogyna). Other tree species sat in between these two ‘extremes’. However, tree age and size did not appear to majorly influence growth rate of ivy stems; asides from if the tree trunk had no extra space for the ivy stems to grow into. In this sense, the growth rate of ivy across trees of all age and sizes (and also species) was not found to be markedly different. In this image, ivy can be seen to have colonised upon the trunks quite significantly, though not yet into the crowns of the trees. Source: Weed Wise. Perhaps these results are not all too surprising, given the longer a tree has been in existence the longer that ivy has the potential to grow up alongside and into the tree’s crown. Granted, a younger tree with a greater trunk diameter than an older tree would, as suggested by the authors, still very likely support better ivy growth. The ‘ascension’ strategy of ivy may be also an important factor in why larger trees are more extensively colonised, however. Because ivy will attach itself to its host via adhesive adventitious roots, larger trees with rough bark (such as Quercus robur) can support ivy far more successfully than a younger tree with smooth bark. In fact, given bark typically roughens quite extensively with age (excluding species such as Fagus sylvatica), it can perhaps also be suggested that older trees are more abale to support significant ivy growth by mere virtue of older age bringing with it the rougher bark. Looking at the crown of a tree, the fact ivy was observed to colonise large oaks of a healthy age is actually quite interesting. Oaks usually have dense foliage crowns, which would mean any constituent ivy is less able to obtain the light it needs to photosynthesise (which is identified, by the authors, as a reason for why ivy will prefer to grow into the crowns of tall trees with smaller leaves and generally lighter foliage crowns). Therefore, we can potentially conclude three things: (1) ivy will ‘rank’ large trunks with rough bark as more important than lighter crowns, (2) the oaks in the study had thin crowns, or (3 – as suggested by the authors) that isolated large trees, even if they have dense crowns, can still provide prferable light conditions (the adverse impact in negligible) for ivy. A more isolated tree also means that its trunk is exposed to more light, which is also beneficial for ivy. This may explain why isolated trunks had more ivy stems than similar trunks in denser stands. Crossing over into urban areas therefore (this study was done in woodland), we can begin to understand why exposed, older, and larger trees (particularly oaks, though interestingly also hawthorns) can become so laden with ivy. Having understood the above, such a sight should perhaps now be wholly understandable. Source: Cronodon. In light (pun intended) of the above therefore, hopefully we can begin to understand what drives ivy colonisation. From looking around on Google Scholar, further articles exist on lianas (and herbaceous vines) of other species and their growth rate / extent upon trees, though it largely appears to be an unexplored topic. Perhaps scope exists for additional research, and particularly for ivy. Source: Castagneri, D., Garbarino, M., & Nola, P., (2013) Host preference and growth patterns of ivy (Hedera helix L.) in a temperate alluvial forest. Plant Ecology. 214 (1). p1-9.

The stumpgrinder, grinding up a... stump?

02/03/16. Fact #165. Trees must feature heavily within urban environments, if the adverse impacts of man-made and artificial landscapes are to be lessened in magnitude. However, in many instances, tree cover is not where it could be. Roadside verges may be void of trees (even those that are rather wide) and other public areas may also be somewhat lacking in tree cover. In an attempt to counteract the harshness of the urban environment, many local authorities (public bodies) are stating their desire to improve the tree cover within their realms, or at least make areas more ‘green’. Many suitable areas likely exist to feasibly support such a pursuit, though what is straightforward on paper may not be so in actuality. In this post, we focus on a case study undertaken in the tree-lacking and intermittently concrete-laden East Baltimore, where the municipal authority is seeking to double the city’s tree cover over the coming years (to 40% canopy cover). Specifically, the study looks at two areas of East Baltimore (Madison-Eastend and Berea), where tree planting en masse is potentially possible (due to a current lack of trees – only one tree for every 83m and 62m of street, respectively!) though, since the 1960s, planting schemes there have routinely failed (at the time, many residents were in opposition to tree planting). In fact, residents in East Baltimore during the 1960s preferred clean concreted areas, and considered trees to be directly in opposition to their values. Locally, they were dubbed “tree rebels”. Since then however, the population of East Baltimore has drastically altered. Gone is the largely European immigrant population, and in its place is a growing community of African Americans that moved in from rural areas. The lack of trees has remained, however. In addition, to reach the 40% canopy cover desires it has been recognised that residents must also start to plant trees in their gardens, as planting street and park trees alone will not enable East Baltimore to reach its target goal of canopy cover. Below, we can observe a broad break-down of existing canopy cover and potential future canopy cover levels if tree planting is successfully completed. Current canopy cover and the potential future canopy cover levels of the two areas in East Baltimore. The authors therefore have two (or three) principal questions to answer: (1) is there ample space to support “aggressive” tree planting regimes, and (2) do current residents of the two areas want more trees and, even if they do, are they willing to support planting schemes. A third question builds on the second one a little, and asks whether the changing ethnic composition of the areas has an influence upon desires relating to tree presence and planting. Madison-Eastend and Berea were selected as areas for the study, as they are near to where the principal “tree rebel” groups were, and are also suitable for accomodating a large-scale increase in tree presence. The two areas also vary enough in terms of house ‘plot’ size (property and surrounding garden) and available public green space (Madison-Eastend is lacking significantly within properties and along roadways, and Berea is most certainly not), which enables for views to be obtained across a wider spectrum. Granted, both areas have ample potential space for trees (as shown below, in the two figures). In Berea, there is a massive amount of space in front and back yards for trees to be planted. Some space also exists along highway verges, and in open spaces. Tree pits also exist, which are currently empty. If needed, more tree pits can be made. Berea contrasts with Madison-Eastend, where we can observe little space along streets and in the grounds of properties to plant trees. Instead, a large park area, and some empty tree pits, will support tree planting. Again, more tree pits can be made, if necessary. In order to obtain the data for the study, the authors interviewed 16 residents from Berea and 10 from Madison-Eastend. The interviews lasted for roughly 15 minutes, and had some form of structure, though did allow for interviewees to diverge from the interview and expand upon other tree-related issues if they so desired. All interviewees were African American. Upon completion, 14 of the 26 interviewees held a generally positive perception of trees. The authors remark that the shading benefits of trees was particularly valued in Madison-Eastend, given the area (and Baltimore as a whole) has a potentially uncomfortably warm and generally humid subtropical climate (exacerbated by the lack of trees, no doubt). For those interviewed in Madison-Eastend who did not have access to shaded locations, the desire for larger trees to bring shade to the area directly outside of properties was particularly evident. If such areas were not available, or even if they were, interviewees would “gravitate” to the side of the street that did not receive direct sunlight. In Berea, interviewees echoed sentiments from those in Madison-Eastend, and even whilst a few streets did already have large trees that cast shade, it was recognised that the urban heat island effect was an issue area-wide as a whole. Remarks were also made as to tree shade reducing costs associated with running air-conditioning systems. A few empty tree pits can be seen here in Madison-Eastend, that have been turned to grass. We can also observe a lack of front yards or gardens. Source: Roadsnacks. Other positive values held by residents interviewed included the amenity value trees provided and their beneficial impacts upon tackling climate change (or just generally improving the environment, because trees are needed for humans to live). Turning towards negatives, interviewees (even those who generally liked trees) stated that the wildlife attracted by trees was annoying – bird poor was a principal nuisance, though insects and also rats were raised as concerns residents had. Tree pollen and its associated allergies was also a concern outlined, with one interviewee stating they didn’t want to have to start taking tablets again to combat their allergic reactions. However, quite selflessly, one interviewee stated that they would champion large-scale tree planting operations, even in spite of their allergic reaction to pollen. A necessary trade-off, they claimed. Overhanging branches and roots entering drain pipes were also issues raised. An interviewee in Berea, for example, exclamated that they did not want trees because of the issues with roots in water pipes. Similarly, an interviewee from Madison-Eastend used an example of vacant properties with tree branches encroaching upon them to outline why trees may be bad. Falling limbs in storms was also a concern, of which limbs from large trees were particularly an issue. Echoing past planting failures, one resident in Madison-Eastend stated that they had watched trees die before, so questioned why the city hadn’t cared for previous trees planted. Perhaps, the same thing will just happen again, they assume. Where dead trees still remained, residents also wished that East Baltimore authorities would remove the dead ones before stating they want to plant more, as the dead trees were not amenable and, in some cases, had been left for over a year without removal. On a more profound level, one resident interviewed was concerned that tree planting en masse would lead to gentrification of the area, meaning a potential destruction or displacement of the community they had grown up within. On a similar note, political agendas were a concern, where trees may simply be planted to further the career of a politician. Drug issues were also a concern, as trees could be a place to hide drugs (that residents were keen to stop occurring at the current high drug-use rates). However, no remarks were made on the concrete landscape being more preferable than one with trees, in contrast to the 1960s era of “tree rebels”. Focussing on aftercare of trees, views were mixed. Some who were interviewed said they would care for the trees, though were concerned other residents nearby would not (or even if they did, children may break them). Others stated that, as so many trees had died before, they were lacking the confidence in any future tree planting schemes being any different. It was also mentioned that whilst homeowners may water trees, those who rent may not (because homeowners have a greater vested interest in the area surrounding their property). Changing culture was also cited as a reason for why aftercare undertaken by residents may be poor. Whilst the initial wave of African Americans was from rural areas who had a closer affinity with nature, the current younger generation grew up in the concreted city landscape. Therefore, would they even care for trees and nature in the same way as the older generation do? In light of the results from the interviews, we can observe how there are mixed views on tree planting and the associated aftercare by residents. Whilst trees bring shade and look good, they may cause mess, not be loved by renters in the same way they may be by homeowners, and be viewed as a vehicle for furthering political agendas. However, because no interviewees stated they preferred concrete landscapes, the views from the 1960s may no longer be held (though we must accept this was a very limited sample size). From this, we can suggest that tree planting to any large degree is far more of a possibility than it once was, and it may be wise to try again. It should also be noted that all points raised both for and against trees were also entirely valid, and would probably be relatively similar for other areas across the western world. Of course, it then comes down to balancing those values aforementioned, and ensuring that current negative views of trees are challenged in a constructive and informative manner. If this can be achieved, the goal of 40% tree cover across Baltimore may become a more achievable dream. Source: Battaglia, M., Buckley, G., Galvin, M., & Grove, M. (2014) It’s not easy going green: obstacles to tree-planting programs in east Baltimore. Cities and the Environment (CATE). 7 (2). Article 6.

That's almost one for r/photoshopbattles.

It's all about doing what is reasonable in light of what is foreseeable, and a resi / PICUS / etc. will supplement understanding both aspects. Nice shots. Ah, so you're German! I take it you don't have The CODIT Principle because you bought the real copy Das CODIT Prinzip.

Get the book, as it's so easy to read and really very good! I'm sure it can be justified as a gift to yourself, but if met with protest then demand that it becomes a gift from someone else. I suppose it becomes a 'lesser of two evils' thing, and notably if we're dealing with a tree in a setting where there is a target zone (so not in the middle of a forest). If there is reason to suspect internal decay, and there is therefore reason to suspect something has to be done to the tree else it might be deemed reasonably likely to cause an issue down the line (this is where expediency comes in), then using such an invasive device to help influence a management decision is most probably going to be justifiable. A bit like that beech we worked on, David. Having identified Kretz (U. deusta), it was evident some form of management was likely going to be necessary, and in that case we'd need to be understanding internal wood proeprties. Using a PICUS would have been feasible, though given it can give improper reading if there are shakes / cracks in the tree, then a Resi is probably the best option. Using this to drill four (five) holes to study the extent of decay, and to subsequent influence (and probably justify) a management decision, then you're covered in two ways: 1. you know what the current state of decay was like at the cross-sections studied 2. you have satiated the desire to justify works, and in light of any hazard manifesting into actuality then there is supporting evidence to add context to why a decision was made to do works A instead of works B or works C. All about painting a picture, and in spite of the issues with invasive devices maybe meaning you run out of red paint slightly too early and finish with too much green, it's still better than not finishing the painting at all (or painting it and having it look absolutely dire). Poor analogy, but hope it makes sense. All I can think of whilst frying eggs at 6 in the morning before college! Oh, and zat German accent ist vunderbar!