(Arboricultural-styled) 'Fact of the Day'

[David Humphries]

I was only kidding.

 

I know

 

 

 

 

.

[Kveldssanger]

I don't know what the costs are, though I am sure Bartlett would. My concern with these sort of things, like as David mentioned, are the non-target impacts. What else are we nackering at the same time? Glynn Percival suggests perhaps a fair amount of other species in places, and in other instances not many, but rarely, if ever, can we get something that only impacts upon the thing we are looking to purge from existence.

[JaySmith]

There was also an article in Essential Arb about injecting garlic into HC's that had bleeding canker, not sure on the results though

 

 

http://www.forestryjournal.co.uk/media/uploads/cat-267/horse-chestnut-garlic-essentialarb-november-issue54.pdf

[Kveldssanger]

I remember that being on the BBC a year or so ago. I hope studies are being done to some extent (whether to be published as peer-reviewed articles or just companies testing compounds), so it'll be interesting if anything comes out in the coming few years on the effects of garlic.

[Kveldssanger]

I just realised we're in December. I've been putting down the month of November for all the posts during December, I think. Tragic!

 

14/12/15. Fact #99.

 

Exactly how the rooting system of a tree will 'branch out' is species-dependent (as is it different between varieties of the same species), as is it dependent upon soil conditions, though it is generally accepted that roots will branch far more readily than the foliage crown will.

 

And so we enter the realm of numbers...

 

Kolesnikov, in his 1966 book Fruit Biology, found that apple seedlings could produce between five and seven orders of lateral roots during one growing season, of which third and fourth-order roots were most abundant. The same research also identified a one-year old Malus prunifolia to have 40,000 roots, with a total length of 230m. Extrapolating this out, it was estimated that a mature tree of the same species may have several million roots that, when laid out lengthways, may amount to several kilometres in distance.

 

Further studies have also been undertaken on other species of tree, and it is evident that there is marked difference between species. In four-month old seedlings of Pinus taeda and Robinia pseudoacacia, 419 and over 7,000 roots were found respectively, of which total root length was 161cm and 32,500cm (again, respectively). Similarly, when a six-month old Pinus taeda were compared with an identically-aged Cornus florida, it was found that the former had 767 roots (amounting to 387cm total length) and the latter 2,657 roots (amounting to 5,144cm in length). The study also highlighted that, due to competition, forest-grown seedlings will have, on average, fewer roots than specimens of the same species grown in isolation.

 

...das ist numberwang!

 

[ame=https://www.youtube.com/watch?v=wJs3Tsx-3Ak]nümberwang[/ame]

 

Source: Head, G. (1973) Shedding of Roots. In Kozlowski, T. (ed.) Shedding of Plant Parts. USA: Academic Press.

[Gary Prentice]

There was also an article in Essential Arb about injecting garlic into HC's that had bleeding canker, not sure on the results though

 

 

http://www.forestryjournal.co.uk/media/uploads/cat-267/horse-chestnut-garlic-essentialarb-november-issue54.pdf

 

Have a look at JCA (Jonathan Cockin and assoc) for more info in this.

[Kveldssanger]

Not sure if any of you guys have read the new AA magazine, but it's got some right cracking articles this edition. Ted Green's and Jeremy Barrell's articles are great, and the one on Bialowezia NP is very interesting (I wish it were longer).

 

Jeremy Barrell doesn't like highway middle managers!

Edited December 14, 2015 by Kveldssanger

[JaySmith]

Have a look at JCA (Jonathan Cockin and assoc) for more info in this.

 

 

I had a look on their website to see if there was any further info but couldn't see anything, do you have a link?

 

Thanks

[Kveldssanger]

15/12/15. Fact #100 (!!).

 

We should all understand what a heart-rot is, some of the fungi that utilise heartwood as their energy source, and the type of heart-rots different fungi may cause (brown rot, white rot, soft rot), though how much do you know about modes of establishment - as in, how exactly do fungi colonise heartwood?

 

It is first important to note that many of the heart-rotting fungi are very slow in their colonisation of their host. Colonisation and decay, such as with Fistulina hepatica on oak, may be very gradual. Because of this fact, and because we are learning more about fungi every single day, methods of colonisation are by no means conclusive, though general 'trends' can be observed.

 

Typically, one would expect that, for heartwood to be colonised, then the heartwood must be exposed to ambient conditions - be this through trunk wounds induced by grazing, fire, and so on, or via wounds to the roots and branches that are substantial enough to possess heartwood. The below table shows how, on Quercus spp., different points of entry may be used by fungi, and the associated extent of decay associated with each point of entry.

 

 

Taking the above into consideration, there are three points of entry that form two common themes. Heart-rotting fungi may enter at the 'top' (branches), at the 'middle' (trunk), or at the 'bottom' (roots), and these can be separated into two classes: top rot (entry via the crown) and butt rot (entry via the lower trunk and roots). In the case of top rot, decay will work its way down the structure, whereas in butt rot the decay will begin in the root collar region and propagate up into the butt.

 

Usually, a species of fungus will fit into one of the categories. For example, Grifola frondosa and Pseudoinonotus dryadeus on oak will cause butt rot, whereas Laetiporus sulphureus and Stereum gausapatum will cause top rot. Therefore, it can be concluded that different fungi employ different strategies for successful colonisation.

 

Expanding upon butt rots that may propagate through the soil, we can observe that species may utilise either soil-borne mycelium (migratory rhizomorphs and root-to-root contact), or even sporulate in the soil. From this, it can be deduced that, where colonisation is via root-to-root contact or rhizomorphic action, the same genotype is colonising the new host as has colonised the prior host(s). Heterobasidion annosum and Armillaria spp. are great examples of where a single genotype may infect many hosts (the former cannot grow rhizomorphs so relies upon root-to-root contact). Conversely, it appears that Phaeolus schweinitzii populations within a stand area may be far more diverse, given its means of propagation is via diospores.

 

Panning-out and looking at colonisation strategy again as a whole, the distinction between the availability of exposed heartwood when comparing the root system to the crown structure is biased heavily in favour of the crown structure (given the aerial structure is more readily battered by biotic and abiotic mechanisms). Thus, it can be posited that where a fungus colonises determines how it colonises - be it exposed heartwood, active pathogenesis, or specialised opportunism. For active pathogenesis for instance, we can observe how Heterbasidion annosum and Armillaria spp. rely upon their own ability to colonise living roots through invasive forces, and how they may even opt to colonise already-stressed roots that are experiencing colonisation by other fungi, are residing within compacted soil, or are suffering from moisture stress.

 

For top rots, we can safely assume that most - if not all - infections are via spores germinating on significant areas of exposed heartwood. For one, there is very little means of one Laetiporus sulphureus (for example only) getting close enough to another tree, and have sufficient innoculum potential, to infect in via active pathogenesis, so this method of colonisation is rendered defunct. Thus, colonisation via spores makes evolutionary sense, and this may make us question whether pruning a tree to an extent that heartwood is exposed is something to be desired.

 

Of course, we cannot unequivocally state that a top rot will always colonise via exposed heartwood. A tree may not have such wounds and be in a location where colonisation is feasible. This is where specialised opportunism characteristically creeps in, after being latent in the discussion for a short while. Stereum guasapatum, for example, commonly establishes via such a method. It will enter the sapwood of branches and, from there, enter into the heartwood of the branch or enter into the heartwood of the adjoined main stem, where it will induce what is termed 'pipe rot'.

 

Specialised opportunism doesn't stop there, however, as an even more clandestine strategy is adopted by Echinodontium tinctorium. This fungus can enter via stubs less then 1cm in diameter upon branches and, as the parent branch grows and begins to - in time - form heartwood, the fungus can begin its colonisation.

 

It goes without saying however that the one limiting factor of heart-rotting fungi is their inability to colonise intact and functional sapwood. This means that fungus will be 'caged' into an area, though this doesn't mean they cannot colonise the heartwood present - which we know may take a very long time (this may even benefit their strategy of colonising heartwood, as by being slower at colonising, they don't use up their food source too quickly). Despite this, some heart-rotting fungi, such as Phellinus spp.., can breach into sapwood from heartwood via active pathogenesis. This can lead to the tree dying, once swathes of sapwood are destroyed (or the tree is girdled).

 

More broadly, heart-rotters need to be able to breach intact sapwood to create sporophores (such as some Phellinus spp., where a progressively-thickening mycelial pad basically 'pushes' out the bark and ruptures it), unless they can fruit out of exposed areas of heartwood. Therefore, where a fungus enters via an exposed heartwood region, it may also use that site for its means of exit, and for species that enter via branch stubs, such as Porodaedalea pini and Echinodontium tinctorium, the branch stubs used for entry will act as the principal means of exit. Go out the door you entered by.

 

A nice image to finish off, showing many possible routes of entry.

 

 

A - large trunk wounds (exposed heartwood)

B - dead branches lacking heartwood (specialised opportunists)

C - in-tact branches containing heartwood where decay starts in sapwood (specialised opportunists)

D - branchlets with (currently) no heartwood (specialised opportunism)

E - buries branch stubs (specialised opportunists)

F - rhizomorphic spread (active pathogenesis)

G - root-to-root contact or grafting

H - equivalent to 'C' but in roots (specialised opprtunists)

I - soil-borne basidiospores

 

Source: Rayner, A. & Boddy, L. (1988) Fungal Decomposition of Wood: Its Biology and Ecology. UK: John Wiley & Sons.

[Kveldssanger]

...yeah, that one turned out to be an essay in itself.