(Arboricultural-styled) 'Fact of the Day'

[Gary Prentice]

I'm sure that 'begs' more than one question.

 

I'm guessing that forward thinking managers/owners etc with an environmental holistic approach will usually have a 'champion' somewhere within the organization. someone with the interest, knowledge and expertise/experience - even charisma, to navigate and steer from within to change the mindset of the organization.

 

Reading through websites, journals etc it's surprising, or not, how often the City of London is involved. I often wonder just how much certain people are involved behind the scenes to generate interest in change?

 

Just my two pence.

[Kveldssanger]

You'd like to think so, that's for certain! An article by Jeremy Barrell in the recent Arb Mag was quite interesting though, and covered that somewhat.

[Kveldssanger]

The below post is something I am sharing from an assignment I wrote recently. It is long, though I hope it is of use to some of you. All sources are at the end, and I strongly suggest the books I have referenced you buy – they’re all absolutely fantastic books. Particular kudos goes to Dujesiefken & Liese’s ‘The CODIT Principle’, which is hands-down brilliant.

 

08/02/16. Fact #147.

 

The compartmentalisation process can be split into four sections, under the banner of two governing parts. The four stages are: (1) wounding, (2) response of the tree to compartmentalise the injury and possible infection, (3) the succession of micro-organisms that seek to actively or passively combat the tree’s natural defence mechanisms, and (4) development of subsequent wood discolouration and decay. The two governing parts are: (1) events that occur within the wood at the time of wounding, and (2) events that occur afterwards (Shigo, 1991). However, there are many aspects that we likely yet do not properly understand, or even understand at all.

 

It is also necessary to recognise that, by default, trees are hugely compartmented (Karban, 2015; Shigo, 1986). Wood is split up by growth rings and radial rays into small sections, single cells are internally compartmented into many different functional units and are themselves segmented into groups by radial and terminal parenchyma, and branches are not conductively attached to the trunk tissue from above. Certain species will also form heartwood, which further compartmentalises the tree. Compartmentalisation is nothing new to a tree, therefore. There is nonetheless a difference – natural growth form leads to high levels of ‘compartmentation’, whilst ‘compartmentalisation’ is a concept that relates to resisting decay exclusively (Shigo, 1986).

 

The overall concept of phenotypic response to infection is determined by not only genetics (Santamour, 1979; Santamour, 1984a; Santamour, 1984b; Shigo, 1986; Shigo, 1991), though also energy levels (Shigo, 1986; Shigo, 1991; Wargo, 1972; Wargo, 1976; Wargo, 1977). Where energy reserves are high, the compartmentalisation of decay will be more effective than if energy levels are low. When a tree that has poor energy reserves is infected, the pathogen will thus have an easier means of establishment internally, further reducing already-depleted reserves. Therefore, CODIT mechanisms, whilst dictated by genetic qualities primarily, are heavily influenced by the energy available to the tree. Without needed energy reserves, not even a mighty oak may be able to compartmentalise effectively.

 

It should also be noted that phenology plays a role in successful defence (Shigo, 1991). All trees have their weak points, and therefore at times the response to wounding will inherently be less favourable, given the traits of the tree. Such a weakness may be exacerbated if the period of acute weakness aligns with the period of maximum strength of the infecting pathogen.

 

In essence, compartmentalisation is a truly dynamic process. Reaction zones are constantly shifting in response to pathogenic activity (sometimes on multiple fronts from multiple wounds). This favours everything involved within the process, as a state of immobility in nature means death. Despite this, the tree always has the upper hand, as the pathogen that wins the battle to begin infecting its host may (1) not be the pathogen that is best-suited to attack the specific host tree, and / or (2) the pathogen does not know what it can expect in terms of resistance by the tree – the tree’s defence system responds to pathogen presence, in a sort of unexpected counter-attacking measure that the pathogen cannot (accurately) anticipate (Shigo, 1986).

 

With all this in mind, we can now explore the effectiveness of the physiological responses a tree will go through following wounding.

 

Physiological changes

 

As previously ascertained, the CODIT model is segmented into the reaction zone (walls I-III), and the barrier zone (wall IV). Whilst all four walls resist the spread of dysfunction, they are not all as effective as one another. In fact, the relative strength of each wall increases from I through to IV.

 

Wall I, which resists vertical spread of dysfunction from the wound site, is not a biological feature. It is nonetheless under strong genetic control. It provides the weakest of all the wall defences, but this makes the most sense when one recognises that a tree requires vascular connectivity and function for all of its life processes – if too many vascular elements are plugged, other problems may arise (Shigo et al., 1977). Additionally, any vertical spread of infection is largely without significant risk, as the new growth rings formed in the years following will ensure the tree retains an element of vascular functionality (Shigo, 1986). Where this wall is particularly weak, extensive vertical columns of discolouration and decay will likely manifest (Shigo, 1991).

 

Tyloses, which are balloon-like structures, form from the parenchyma cells that border the vascular tissues, and thus facilitate with the plugging of conductive vessels within angiosperms. The pits, which border the vessels, ensure vascular functionality is retained by promoting the localised lateral movement of water around the plugged vessels (Watson, 2006). This adaption ensures the tree can still operate with relative efficiency. Further, depending on the abundance of parenchyma cells around the vessels, the effectiveness of wall I may be very weak or rather robust. Quercus spp. do, for instance, have parenchyma cells that surround all large vessels in the earlywood, whereas other species may only see parenchyma cells surround a portion of the vessels – Ulmus spp. are but one genus with this characteristic, as their earlywood vessels are so massive and latewood vessels are so densely clustered together that parenchyma cells cannot envelop the entire vascular network. However, the vessel structure of elm means that wood is essentially more air than it is wood, which also acts as a defensive mechanism against pathogen invasion (Shigo, 1986).

 

Tyloses (T) entirely plugging a vessel within a wounded Quercus sp. (Dujesiefken & Liese, 2015).

 

In particular species, the tyloses are also suberised – Prunus avium, Quercus rubra, and Ulmus americana are just three examples (Biggs, 1987). Such suberisation will aid with the ability of wall I to resist pathogenic spread in a vertical manner, though this does not cause the wall to rank above others in terms of efficacy.

 

The second wall, which resists inward spread of dysfunction, is also not a biological feature and is, too, under strong genetic control. This wall is stronger than the first wall, and is strengthened post-wounding by tyloses and suberin within parenchyma cells (Shigo et al., 1977). Wall II is able to be ‘defeated’ by pathogens relatively easily, however – particularly in diffuse-porous woods, where latewood cells are not as densely clustered. The propensity of the wall being breached, therefore, ultimately relates to the thickness of the terminal parenchyma band within the previous year’s latewood – Ulmus spp. will suffer, as their terminal parenchyma are very thinly spread (Shigo, 1986). Where this wall is breached, a deep decay column will form (Shigo, 1991).

 

Radial parenchyma (P), terminal parenchyma (white arrows), and vessels (V) of Acer rubrum under the microscope. (Shigo, 1986).

 

Wall III, which constitutes the existing radial rays within the wood structure, much like wall II, is strengthened post-wounding. This wall provides a better likelihood of protection against decay than the first and second walls respectively, mainly because (at least in broadleaves; not so much on conifers) the radial parenchyma sheets are very thick (many single sheets of parenchyma cells very close together) (Shigo, 1986; Shigo et al., 1977; Thomas, 2000). The fact that no ray will come into contact with another ray is a further safeguarding measure (Dujesiefken & Liese, 2015), as this nullifies the risk of a fungal pathogen using rays as vectors for internal establishment. An increased abundance of radial parenchyma sheets will also impact beneficially upon efficacy of this wall. Where this wall fails, decay will spread inwards and laterally. Where it is successful, decay will be ‘channelled’ between the two successful rays. Depending on the success of wall II however, the decay may still propagate deep into the wood structure (Shigo, 1986; Shigo, 1991).

 

The barrier zone, or wall IV, differs from the reaction zone walls I-III, in the sense that the resultant structure is anatomically different, and separates infected wood from the healthy wood laid down following wounding. Formed from living parenchyma tissues within the cambium that existed at the time of wounding, the barrier zone is initially heavily lignified, though over time suberin accumulates within the new cells’ walls and provides these cells with an impermeable property, preventing propagation of the pathogen into the ‘new wood’ (Biggs, 1985; Biggs, 1986; Shigo, 1986). As already elucidated to, the rate of suberin accumulation and its overall abundance will impact upon success of the wall. The form that the barrier zone adopts is influenced by wound severity, the time of wounding, the species of invading pathogen(s), and the host-specific traits. Some species will form very strong barrier zones and weak reaction zones, whilst other species may be inversely-specialised (Shigo, 1991).

 

The densely-arranged barrier zone (B), separating the discoloured wood below from the woundwood above (Dujesiefken & Liese, 2015).

 

Decay rarely spans out into the new vascular tissues laid down following wounding, as the barrier zone is comprised of short parenchyma cells. Further, as the new wood of the barrier zone is hydraulically and structurally ‘sound’, it is free of dysfunction and therefore highly resistant to decaying organisms (Lonsdale, 1999; Shigo, 1991); that is, unless, another wound occurs in the new barrier zone tissues, at which point the process begins again. At times, this new wound can be self-inflicted, as the barrier zone is prone to splitting under loading conditions. This is caused by the propensity for the rolling woundwood ribs to not properly adjoin – the rolling ribs may, at times, turn inward, creating radial ‘shakes’ that act as internal cracks (Shigo, 1986). An incompletely closed wound may also provide an excellent environment for fungal pathogens, and it is possible that pathogenic micro-organisms influence the direction of growth of new vascular cambium (Blanchette & Biggs, 1992). The barrier zone also doesn’t actually aid with structural stabilisation very well – its role is to retain the tree’s functional integrity, and not so much its structural integrity (Shigo et al., 1977). Alternatively, the barrier zone can be broken by insect borers. In fact, insects are rather common in trees where wounding has occurred, as the decaying wood within is an ideal substrate for larvae. Such tunnelling by the insect therefore penetrates through barriers, and the tree cannot do anything but look to further wall-off itself (Shigo, 1986), which makes it progressively harder to repeat the same processes as there is less energy available for storage and thus for use.

 

Interestingly, despite the barrier zone’s resistance to the spread of dysfunction into new wood, certain species of fungi, such as Inonotus hispidus, can penetrate the barrier zone (Lonsdale, 1999; Thomas, 2000). Furthermore, the wounding site is most beneficial to fungal growth when woundwood has almost occluded the wound, though once closed, fungal infection of the site will usually stop (unless oxygen is supplied from elsewhere) (Shigo, 1986).

 

Ultimately however, even when walls I-III fail, wall IV is usually steadfast in its defence.

 

Further comments regarding physiological changes

 

The reaction zone (walls I-III) is, in the best cases, able to fully restrict fungal infection further into the wood after wounding, though the success of the reaction zone is largely related to carbohydrate availability in adjacent tissues, in addition to ample water so to combat against the transpirational loss triggered by the death of the exposed wound area’s xylem tissues. Such water stress in particular can cause wood to dry out further away from the wounding site, therefore improving the conditions for successful fungal establishment (Lonsdale, 1999). One can therefore stipulate that the health of the tree prior to wounding plays a significant role in the ability for the tree to resist the fungal attack. It should be noted here that seasonal changes in carbohydrate reserves, and the accompanying changes in wood moisture content, have been shown to alter successful invasion rates of fungi such as Chondrostereum purpureum (Schwarze & Baum, 2000).

 

Furthermore, the reaction zone is not structurally homogeneous and does not therefore form a continuously-similar morphological barrier to the ingress of air and / or fungal attack (Schwarze & Baum, 2000). The research by Schwarze & Baum (2000) also demonstrates that, where reaction zones should migrate alongside the internal progression of fungal pathogens (or other dysfunction), various fungal species (such as Ganoderma adspersum, Inonotus hispidus, and Kretzschmaria deusta) are able to extend into functional sapwood some way beyond the reaction zone, whilst not stimulating the simultaneous migration of the reaction zone. Instead, a new reaction zone forms later at the new colonization front and, much like its predecessor, there is no guarantee this reaction zone won’t befall the same fate.

 

Starch grains (arrows) inside tissues, adjacent to vessels, within the sapwood system (Dujesiefken & Liese, 2015).

 

However, one must recognise that trees may have hundreds – if not thousands – of decayed and discoloured patches amongst their structure. By-and-large, the compartmentalisation process is successful, and most injuries are small (from small insect bore holes, dead twigs, etc), though it only takes one instance of failure (usually with more serious wounds) for dysfunction of any kind to wreak havoc on the tree’s system. This risk also increases over time, after each instance of compartmentalisation, as the locked-away resources and storage parenchyma cells cannot be accessed or used any longer (Shigo, 1986).

 

Furthermore, the chemically-strengthened reaction zone around a wound is, in addition to being loaded with suberin and parenchyma cells, laden with phenolic compounds that act as a toxin to most pathogens present. These phenols are toxic not only to invading micro-organisms, but also to the tree itself (Shigo et al., 1977). Despite this, substantial degradation of phenolic compounds by Ganoderma adspersum and Ganoderma resinaceum has been observed in a range of broadleaved species (Schwarze & Baum, 2000). Therefore, phenols are not necessarily an absolutely sure-fire combatant against fungal pathogenicity. In essence however, the tree segments part of its structure to act as the sacrificial lamb. Of course, the tree most usually survives because, alongside the fortification provided by the reaction zone it is also generating new, healthy wood from the cambium, though it should be noted that a tree cannot fully compartmentalise all of its structure as in doing so it will die (Shigo, 1991) – there comes a point where compartmentalisation simply cannot occur any further, as the loss in accessible parenchyma cells for energy storage reaches a critical point where life processes cannot be sustained.

 

Diverting attention again towards the barrier zone, it is necessary to recognise that the production of callus tissue, the subsequent cellular differentiation within the vascular cambium of the callus, and the eventual closure of the wound (which usually results in fully functional vascular connectivity), occurs following wounds inflicted only up to the depth of the xylem – heartwood, or inactive wood, void of parenchyma cells that can morphologically differentiate into necessary tissues, is unable to respond to wounding in the same manner that sapwood can (Neely, 1988b; Shigo, 1986). The amount and rate of callus production following wounding will of course vary between and within species, the size of the wound, the location of the wound on the tree, and the local environmental conditions (light availability, rainfall patterns, and so on). For example, the higher on the stem an injury is located, the faster the wound is closed. Further, young and small trees overgrow wounds more effectively when compared to older or thicker trees (Neely, 1988a; Schneuwly-Bollschweiler & Schneuwly, 2012).

 

After significant wounding, trees might even produce additional sapwood and also stall heartwood formation, in order to bolster parenchyma cell abundance within the wounded region (or even throughout the entire circumference) (Shigo, 1991). Additionally, radial growth increases following wounding have been observed where drill bits were drilled nearly all of the way through the tree, though did not touch the cambium on the opposite side to the entry point. Curiously, the results of the drill tests indicate that the cambium tissue reacts even when not touched (or directly associated with the problem), and receives signals via the symplastic components of the overall structure (Shigo, 1986) – this crucial vascular connectivity further adds context to the reason why wall I is the weakest of the four walls.

 

Moving away from the four walls on an exclusive basis and broadening the horizons of resistance to dysfunction as a whole, there are many other observable physiological mechanisms that a tree goes through following wounding. One significant aspect of resisting pathogens, whilst previously described in brief, is suberin accumulation. Suberin accumulation is an important process within the cell walls of new tissues that have formed after wounding, but before the internal spread of the pathogen is resisted to any marked degree. It does also occur within the lamella on the inner wall of a cell, which is already present at the time of wounding, though this lamella differentiates into a ligno-suberized layer following any such wounding (Biggs & Miles, 1988). The rate at which an infected site can accumulate suberin is directly related to the resistance to pathogen spread, as established. Therefore, trees that can flush the wound site with suberin stand a better chance of resisting infection (Biggs & Miles, 1985). However, suberin accumulation typically works in conjunction with, in angiosperms, the tyloses’ ‘plugging’ of conductive vessels. Suberin, on an exclusive basis, is not normally able to form homogeneous resistance (Biggs, 1987).

 

Furthermore, suberin and its relation to the barrier zone (it is present as a lining of the cells present within the barrier zone) is very much evident, and its abundance will therefore have direct relevance to the success of the barrier zone (Shigo et al., 1977; Shigo, 1986). Suberin is ultimately what provides the fourth wall with its microbial resistance; many – but not all – fungal species cannot break down suberin (Biggs, 1987). Additionally, the accumulation of suberin (and lignin) within the boundary zone is reliant upon temperature, with 0°C being the threshold (Biggs, 1986). For wounds to completely lignify and suberise therefore, it may take many hundreds of ‘degree days’, and thus the rate of ligno-suberisation absolutely impacts upon the resistance of the barrier zone to infection. Wounds will also decrease in infection potential over time as they lignify and suberise (Watson, 2006), with a more rapid process, which is related to preferred temperatures (that will vary between species), aiding with a more swift decline in infection potential (Biggs, 1986).

 

It is critical to note, however, that suberin is only produced by living cells (Deflorio et al., 2008), and therefore if a wound extends into the heartwood then suberin cannot play a role in particular areas of the wound (those spanning outside of the sapwood region). However, heartwood can ‘compartmentalise’. Where it is wounded, a boundary is formed of enzymes that react with oxygen or in response to the presence of chemical secretions by micro-organisms (Shigo, 1986; Shigo, 1991). Such chemical alteration of the heartwood ensures that fungal pathogens do not have free-reign of the heartwood. Interestingly, heartwood that has very high concentrations of extractives is generally found to be within the longest-lived trees (Shigo, 1986) – heartwood therefore is critical in the overall compartmentalisation process, without question. Pathogens will eventually break down the extractive-rich heartwood, however. The process is simply much slower. At this point, it is worth noting that tree species with false heartwood (including Acer spp., Fagus spp., Fraxinus spp.) do not form their ‘heartwood’ (that is simply a discoloured central column) regularly, but instead form such discoloured wood following branch death. The discoloured wood serves the same purpose as heartwood does, by-and-large. Discolouration in false heartwood species is initially a light pink to orange, with the wood only darkening upon infection (Shigo, 1986).

 

In some species, such as Acer spp. and Betula spp., injuries made in very late winter or early spring may ooze or drip sap for some days to weeks afterwards (Shigo, 1986). This is a normal response and aids with creating undesirable (anaerobic) conditions at the wounding site for micro-organisms. Conifers do the same with traumatic resin ducts (canals). As the sap clogs the vessels, oxygen availability progressively decreases. Because wood-decay fungi are aerobes, they cannot function where the sap has clogged the region. Further, the pressure flow is outward, not inward (Dujesiefken & Liese, 2015; Shigo, 1986; Shigo, 1991).

 

Sources:

 

Biggs, A. (1985) Suberized boundary zones and the chronology of wound response in tree bark. Phytopathology. 75 (11). p1191-1195.

 

Biggs, A. (1986) Prediction of lignin and suberin deposition in boundary zone tissue of wounded tree bark using accumulated degree days. Journal of the American Society for Horticultural Science. 111 (5). p757-760.

 

Biggs, A. (1987) Occurrence and location of suberin in wound reaction zones in xylem of 17 tree species. Phytopathology. 77 (5). p718-725.

 

Biggs, A. & Miles, N. (1985) Suberin deposition as a measure of wound response in peach bark. HortScience. 20 (5). p903-905.

 

Biggs, A. & Miles, N. (1988) Association of suberin formation in uninoculated wounds with susceptibility to Leucostoma cincta and L. persoonii in various peach cultivars. Phytopathology. 78 (8). p1070-1074.

 

Blanchette, R. & Biggs, A. (1992) Defence mechanisms of woody plants against fungi. Hong Kong: Springer.

 

Deflorio, G., Johnson, C., Fink, S., & Schwarze, F.. (2008) Decay development in living sapwood of coniferous and deciduous trees inoculated with six wood decay fungi. Forest Ecology and Management. 255 (7). p2373-2383.

 

Dujesiefken, D. & Liese, W. (2015) The CODIT Principle: Implications for Best Practices. USA: International Society of Arboriculture.

 

Karban, R. (2015) Plant Sensing & Communication. USA: University of Chicago Press.

 

Lonsdale, D. (1999) Principles of Tree Hazard Assessment and Management (Research for Amenity Trees 7). London: HMSO.

 

Neely, D. (1988a) Tree wound closure. Journal of Arboriculture. 14 (6). p148-152.

 

Neely, D. (1988b) Wound closure rates on trees. Journal of Arboriculture. 14 (10). p250-254.

 

Santamour, F. (1979) Inheritance of wound compartmentalization in soft maples. Journal of Arboriculture. 5 (10). p220-225.

 

Santamour, F. (1984a) Early selection for wound compartmentalization potential in woody plants. Journal of Environmental Horticulture. 2 (4). p126-128.

 

Santamour, F. (1984b) Wound Compartmentalization in Cultivars of Acer, Gleditsia, and Other Genera. Journal of Environmental Horticulture. 2 (4). p123-125.

 

Schneuwly-Bollschweiler, M. & Schneuwly, D. (2012) How fast do European conifers overgrow wounds inflicted by rockfall?. Tree Physiology. 32 (8). p968-975.

 

Schwarze, F. & Baum, S. (2000) Mechanisms of reaction zone penetration by decay fungi in wood of beech (Fagus sylvatica). New Phytologist. 146 (1). p129-140.

 

Shigo, A. (1986) A New Tree Biology. USA: Shigo and Trees Associates.

 

Shigo, A. (1991) Modern Arboriculture. USA: Shigo and Trees Associates.

 

Shigo, A., Marx, H., & Carroll, D. (1977) Compartmentalization of decay in trees. USDA Forest Service Agricultural Information Bulletin 405.

 

Thomas, P. (2000) Trees: Their Natural History. UK: Cambridge University Press.

 

Wargo, P. (1972) Defoliation-induced chemical changes in sugar maple roots stimulate growth of Armillaria mellea. Phytopathology. 62 (11). p1278-1283.

 

Wargo, P. (1976) Variation of starch content among and within roots of red and white oak trees. Forest Science. 22 (4). p468-471.

 

Wargo, P. (1977) Wound closure in sugar maple: adverse effects of defoliation. Canadian Journal of Forest Research. 7 (2). p410-414.

 

Watson, B. (2006) Trees – Their Use, Management, Cultivation, and Biology. India: The Crowood Press.

[Kveldssanger]

09/02/16. Fact #148.

 

As the climate changes, the phenology of constituent tree species will also change. For example, bud burst may be earlier or later, as may fruit production, leaf fall, and so on. Therefore, in Japan, where spring is marked by the blossoming of the cherry trees, phenological changes may have a marked impact upon how festivals associated with the spring blossom are organised. Thus, the purpose of this study was to determine whether residents of Japan recognise the association between the changing climate and the timing of cherry blossom, with particular focus on those involved with arranging the blossom festivals and those businesses who benefit from them.

 

Three sites were the focus of this study – two in rural areas (Kakunodate and Komoro), and one in an urban location (Nakano-ku). Collectively, the tree sites attract an estimated 1,500,000 visitors per year, during April and May (1,000,000 of which go to Kakunodate). The authors held personal interviews with the organisers of these three festivals (including staff and local government employees), and the managers of businesses who greatly benefit from the festivals taking place (food shops, in particular). During the interviews, questions were asked such as how the individual viewed climate change, what they considered to be impacting upon the changing climate, and how they felt the changing climate would affect the blossom festivals. In total, 28 questions were asked to each organiser and the average time taken to complete the interview was 40 minutes, whilst 12 questions were asked to bussiness owners and the average time taken was 10 minutes.

 

The blossom festival in Kakunodate attracts around 1,000,000 visitors during April and May, every year. Here we can see a fantastic cherry-lined river. Just beneath the trees we can see a walkway full with visitors. Source: Japan Times.

 

Of the organisers interviewed, 92% of them said they felt climate change (global warming) was indeed occurring – the rest were unsure. In relation to festival-specific impacts, how organisers felt about a festival potentially missing the blossoming period (due to climate change) was highly varied (see below images), with organisers at Kakunodate being very concerned, and organisers at the other two locations not being overly concerned (if at all). The argument made the the organisers of the latter two was that people would still turn up to the festivals, perhaps because it’s a cultural thing that may exist independently from the blossoming itself. However, many managers of bussinesses were concerned over the festival’s timing. Those concerned stated that people may not frequent their shops if the festival missed the blossoming period. Despite this, some managers were relaxed about the issue, and felt they would not lose out on custom.

 

A few of the concerned organisers as Kakunodate, in response to the potentially changing blossoming period, said they would absolutely change the festival date to fit with the time of the blossom – this is not surprising. However, most of the organisers of all three festival sites stated they would only consider changing the festival time to fit with the blossom. The organisers of the two sites that were less worried about the festival timing not coinciding with the time of blossoming more notably held this attitude, though these two sites did have far fewer organisers involved (as they are smaller events).

 

The responses by the individuals questioned to: ‘‘What if the festival missed the blossoms?”

 

‘‘How can you and the festival / store cope with the change in flower timing?” was the question asked in this instance.

 

With regards to shop managers, many were not prepared to change as a result of the changing phenology of cherry trees. Businesses would operate as usual. However, as most managers interviewed were based at Kakunodate, this result may be somewhat skewed. Certain managers were prepared to plant cherry trees that blossom later, however – this would ensure that any change in phenology of the cherry trees did not fully divorce the festival from the blossoming period.

 

In terms of what individuals thought they could do to reduce their impact upon the changing climate, most suggested they could not use their cars so much, reduce on the amount of waste they produce, and so on. However, two individuals stated that they felt they were impotent, and there was a limit to what an individual can do.

 

From this study, we can see that the response individual stakeholders have to how climate change will impact upon blossoming times varies. In Kakunodate, where the festival is huge (attracting 1,000,000 visitors each year), organisers and shop managers were clearly more worried about the festival missing the blossoming period, when compared to the other two areas. This really is not something that is all too surprising, as the potential economic loss will be much greater (and for a rural economy, where other means of income may be less abundant). Furthermore, the fact that individuals also stated that they recognised climate change was occurring because of the changing blossom times, means that a culturally-important event such as this can be used to educate Japanese residents about how climate change can impact upon the ecological world.

 

A group of blossoming cherries in Nakano, Tokyo. This festival attracts around 250,000 visitors per year. Source: Weepingredorger.

 

Certainly, it would be interesting to see larger-scale studies undertaken across Japan, with focus also on those who visit the festivals. There is a huge risk of organisers and businesses owners being markedly biased in their response, with their concerns over the economic impact climate change may have upon their ability to operate at a profit clouding wider judgement and heavily influencing opinion. In addition, the study is automatically narrowed a great extent by removing a huge potential pool of data (visitors to the festivals), so the results should not necessarily be treated as highly indicative of the thoughts of the wider Japanese demographic (though the authors do recognise this). Even so, an interesting study that certainly makes you think, and is a wonderful foundation to build from in terms of research. It’s great to see such a topic being studied.

 

Source: Sakurai, R., Jacobson, S.K., Kobori, H., Primack, R., Oka, K., Komatsu, N., & Machida, R. (2011) Culture and climate change: Japanese cherry blossom festivals and stakeholders’ knowledge and attitudes about global climate change. Biological Conservation. 144 (1). p654-658.

[Kveldssanger]

Doing a lot of my Lvl 4 stuff these last few days as I am at an ATF meet on Saturday, so will get back to stuff come Saturday evening hopefully. May get something done tomorrow - will see. Cheers guys.

[Pete Hart]

How on earth do you manage to spare the time to put up these fascinating and very informative posts whilst doing your level 4?! I'm currently doing level 4 too and I don't have spare time to eat properly let alone enlighten arbtalk with so much arboricultural knowledge!!

[Kveldssanger]

Thanks for the kind words. To be honest, I force myself. Got one last part of an assignment to do for Wednesday, else I just grind it out in my spare time. I enjoy keeping myself busy, and find that once I furiously pedal for a brief period of time it's easy to keep up the momentum. I do need rests at times however, though usually for only a day or so. And as I have said before, I don't have kids!

 

Also, having been to university I know how to trawl the net for information (Google Scholar, mainly). I also have a very large library, which cost quite a lot of money that I had saved.

 

Oh, my girlfriend is also very understanding!

 

As for how long these take me (if you're curious), usually 60-90 minutes. I like to spend approx 2 hours doing my blog each day, assuming I can. These posts all go to there, as do photos I find and other little bits I share.

Edited February 12, 2016 by Kveldssanger

[Kveldssanger]

12/09/16. Fact #149.

 

Within managed woodlands, deadwood is usually significantly lacking. This may be because deadwood (both standing and fallen) is removed during extraction processes, or because stands are felled before an age where the woodland would naturally begin to accumulate deadwood. Cause aside however, the lack of deadwood (particularly larger fragments of over 10cm in diameter) is bad news for saproxylic insects. Conversely, where deadwood is allowed to accumulate (usually via lapsed management; at times perhaps “benign neglect”), the suitability of a woodland for such insects is enhanced. Additionally, as saproxylic insects may vary in their host preference, a site with a variety of tree species is likely to yield a larger and more diverse population.

 

In the feature study of this article, an investigation was commissioned into how such a “benign neglect” strategy impacts upon saproxylic beetle populations. The location of the study was the Bavarian Forest National Park (Germany) – which employed such a tactic in managing areas of the park (for Ips typographus, at least partially) – and focussed on assessing the relationship between beetle populations and host specifity, and also the minimum threshold of deadwood to support “comprehensive” beetle populations.

 

The Bavarian Forest National Park covers an area that is around 24,500ha, and stand compositions varies across altidunial ranges. At higher altitudes of 1,150-1,430m, Picea abies (Norway spruce) is the dominant species, whilst at lower altitudes above 650m stands consist predominantly of silver fir (Abies alba), beech (Fagus sylvatica), and spruce (Picea abies). Until the 19th century, these stands were largely unmanaged, and were therefore old-growth forests with a likely abundance of deadwood (and associated beetle species). However, once forestry practices were introduced, old-growth stands became highly fragmented and exist today in patches normally no greater than 100ha. This change in stand structure lead to some beetle species becoming extinct. At this point in time therefore, the national park can be segmented into three categories: (1) old-growth forest, where there are many trees of over 400 years in age and there has been no logging for over 50 years; (2) unmanaged forest, where bark beetle-infected (Ips typographus) trees are left, and; (3) managed forest, where bark beetle-infected trees are actively salvaged for timber through the logging process (“salvage logging”). The site is (evidently) home to the bark beetle, which is causing mortality of many spruce trees.

 

Dead spruce stands, caused by Ips typographus colonisation. Beneath, re-growth can be observed. Canopy openness is very high, as is deadwood abundance. Source: Environment and Society Portal.

 

In this study, from the three above-mentioned stand categories, the authors identified a total of 293 plots at 0.1ha each. These plots also spanned across the entire altitudinal range of the park. From these, a randomly-selected 126 were surveyed for saproxylic beetles (21 in old-growth, 52 in unmanaged forests, and 53 in managed forests). Surveying for insects involved pitfall traps, flight traps, and direct searching. In these locations, deadwood accumulation was also calculated. All deadwood was categorised by species, and the minimum threshold for a piece of deadwood being calculated was 12cm in diameter.

 

From the deadwood recorded across each stand type, there was a discernible difference between deadwood presence in unmanaged stands and managed stands (see the below figure). Interestingly, old-growth forests had less deadwood than unmanaged sites, though this may be because the bark beetles in the unmanaged sites were causing marked deadwood accumulations (and such deadwood was not removed, unlike in salvage-logged sites). In addition, old-growth relicts were previously logged (as little as 51 years prior to the study). Furthermore, perhaps the stands had peaked and were now declining in deadwood abundance, because the dominance of large and mature trees would have ‘seen off’ competition many years previously. Any deadwood associated with a loss in competition would have since been degraded by fungi and insects.

 

Other variables recorded were the ‘penetration rate’ of bark beetles (Ips typographus) into spruce hosts (higher rates were associated with higher canopy ‘openness’), ‘senility’ (deadwood from individual fir and beech trees in a state of serious decline), and ‘control’ (altitude and habitat continuity).

 

The difference in deadwood abundance across the range of stand types, separated by species.

 

In relation to the species diversity and abundance of saproxylic beetles (excluding Ips typographus), 12,253 individuals were found from 280 species. 244 beetle species were found through the use of flight traps (103 exclusively), 164 by direct searching (22 exclusively), and 33 by pitfall trap (1 exclusively). 78 of the 280 species (27.8%) were red-listed.

 

Of all the species, 113 were generalist, 90 were found exclusively in coniferous deadwood, and 77 were found exclusively in broadleaved deadwood. Greater total populations were found when there were a greater number of species present (as shown by the graph below). However, the presence of Ips typographus was found to be significant in terms of its impact upon populations of other beetle species found only in coniferous deadwood (of which some were red-listed). Single-tree senility of beech and fir was found to be the biggest driver of broadleaved specialist presence, whilst the increasing penetration rate of the bark beetle was found to be the sole driver of increasing coniferous specialists (though not so for red-listed species, where numbers declined at higher penetration rates). Generalist species simply benefited from a greater abundance of deadwood.

 

How total beetle population correlated with total beetle species, for each site surveyed.

 

Across all sites and for all beetle species, it was found that an increase in canopy openness and deadwood abundance (‘resources’) lead to an increase in beetle populations. In this sense, it can be stated that more resources in a more preferable setting will provide habitat for more individuals of a greater number of species. As a matter of fact, population increases were rapid in response to even only a moderate increase in such resources, across generalist and specialist beetle species. Even where bark beetles did colonise spruce stands, the resultant increase in deadwood was beneficial for many beetle species, and therefore the bark beetle could be described as beneficial for other saproxylic beetles that specialise in conifers. This may, in part, be because of the bark beetle’s effect of opening up canopies, folowing death of the host spruce. However, stand openess had a negative effect upon broadleaved specialists, and this may be because broadleaved specialists are more likely to be fungivores (and fungi specialise in cool, humid, and thus low-light conditions). For red-listed species exclusively, deadwood presence in ‘naturally disturbed’ (as in, not logged) stands is most important.

 

Of course, certain beetle species will fare more preferably in open stands with a high amount of deadwood, whilst others will frequent closed canopies with less deadwood. Despite this, where there is little deadwood, beetle communities may become ‘impoverished’ (suffer from ‘famine’), and there are typically more beetle species in open stands with high amounts of deadwood than in closed stands. In this sense therefore, there is a minimum viable deadwood presence, for all species of beetle – it simply varies depending upon the species, which is not surprising. Unfortunately, the authors did not specify conclusive thresholds, and state that it is hard to calculate them because species may respond differently to differing amounts of deadwood, and there may not necessarily be a ‘cut-off’ point, but simply a continued (and perhaps steady) decline in population until there is not one at all. Highly intricate research would be required to calculate such thresholds, that would need to also be species-specific.

 

Fallen and standing deadwood within a dense mixed forest stand within the Bavarian Forest (there are more incredible photos to see via the source link). Source: Philip Klinger.

 

In spite of this, the authors do recommend that for dense stands of mixed woodland, canopy openness should be around 20%, and the abundance of deadwood from beech and fir should be increased to 30-60 cubic metres per hectare (at least). For more open stands (20-50% canopy openness, or greater), the focus should be only to increase deadwood abundance (to similar amounts as in denser stands). Where stands are logged therefore, retaining deadwood to such amounts would be beneficial in a conservation sense.

 

This is all certainly highly complex therefore, and from reading the paper somewhat taxing to digest (at times!). Granted, because beetle species are highly variable in their preferences, a broad study such as this is always to be welcomed as it ‘sets up the playing field’. Despite this, the authors note that this is research that shoud be defined only as a case study – other sites may vary in their characteristics, constituent populations, and thus ‘ideal’ states. Nevertheless, for montane stands in Central Europe, this research may be considered very important. Perhaps the most critical thing we can draw from this is that managed stands need more deadwood – period. Because beetle diversity and populations incresed alongside deadwood presence, the openness created by logging could perhaps be a good thing when compiled with the selected retention of deadwood – at least, for species that are not red-listed (as these require disturbance only of natural origin, of which logging is not).

 

Source: Müller, J., Noss, R., Bussler, H., & Brandl, R. (2010) Learning from a “benign neglect strategy” in a national park: Response of saproxylic beetles to dead wood accumulation. Biological Conservation. 143 (11). p2559-2569.

[Pete Hart]

Fair play! Having also done a degree I'd say the level 4 makes that look like a walk in the park. I'm also lucky to have a big library of books but boy this course has consumed me and completely taken over my life!

Keep up the good work 👍

[Kveldssanger]

Agreed, my BSc was a doddle compared to this! Wrote more already than I did for the entirety of university, I'd say. And they have pointless word limits for university reports, too!

 

Back to normal tomorrow. Just got back from an ATF (Ancient Tree Forum) site visit today, so been uploading photos to my blog and just sorting stuff out. Trying to decide what some of the fungi are, as I have forgotten or am unsure! Knowing my luck, they'll all be Laetiporus sulphureus!