Why does Meripilus giganteus attack and decay the underside of roots?

[heeilbeck]

Just wondering how and why does Meripilus giganteus attack and decay the underside of tree roots?

[David Humphries]

Tree roots don't grow like branch wood. As they age they lay down new wood at the sides and top and less and less at the bottom. Eventually this wood is dysfunctional and fair game for the mycelium of Merripilus giganteus.

 

Andrew Cowan produced a great diagram of this process of root morphology.

 

I'll try and dig it out.

 

 

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[daltontrees]

Tree roots don't grow like branch wood. As they age they lay down new wood at the sides and top and less and less at the bottom. Eventually this wood is dysfunctional and fair game for the mycelium of Merripilus giganteus.

 

Andrew Cowan produced a great diagram of this process of root morphology.

 

I'll try and dig it out.

 

.

 

David, do you know whether this process is giverned by any tropisms or is the curtailment of underside growth largely (or wholly) because of the steady increase in loading on the underside as the tree grows and sways, crushing or inhibiting the cambium?

[David Humphries]

David, do you know whether this process is giverned by any tropisms or is the curtailment of underside growth largely (or wholly) because of the steady increase in loading on the underside as the tree grows and sways, crushing or inhibiting the cambium?

 

If I'm honest Julian, I don't recall reading anything specifically relating to why (but, I'd guess it will have been covered in a number of the usual suspects)

 

I'd imagine that it will probably be a combination of biomechanics & physiology.

 

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[David Humphries]

Tree roots don't grow like branch wood. As they age they lay down new wood at the sides and top and less and less at the bottom. Eventually this wood is dysfunctional and fair game for the mycelium of Merripilus giganteus.

 

Andrew Cowan produced a great diagram of this process of root morphology.

 

I'll try and dig it out.

 

I'm sure Andrew won't mind me using this, as he posted it on previous threads many moons ago.

 

Based on his observations, he illustrates how roots (oak in this case) can morph over many decades in coexistance with Grifola frondosa which is a similar association (but potentially less aggresive than...) Meripilus & beech.

 

 

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[heeilbeck]

Thanks for the explanation! I've come across the subject in literature while doing an assignment, but haven't been able to find out why!

[David Humphries]

it can be pretty disconcerting when you listen to Merip decayed roots on beech, we've come across some examples where the upper section of the roots are hard and relatively vascular but sound like a clay land drain when tapped.

 

 

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[David Humphries]

....we've come across some examples where the upper section of the roots are hard and relatively vascular but sound like a clay land drain when tapped.

 

and others where the roots are dense and sound solid

 

(probably where the decay is less aggresive or at an earlier stage)

 

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[daltontrees]

If I'm honest Julian, I don't recall reading anything specifically relating to why (but, I'd guess it will have been covered in a number of the usual suspects)

 

I'd imagine that it will probably be a combination of biomechanics & physiology.

 

.

 

I shall have a bedtime browse of Roberts Jackson & Smith. If I unearth (pun not intended) anything I'll share it here.

[daltontrees]

This book has yielded nothing specific. hve tried 'Fungal Strategies...' too but again nothing altough it does mention that Meripilus can infect a tree through a dead tap root. All this is saying though is that M.g shos a sapwood exposed strategy. I spotted also that some attempts to infect healthy wood had failed (Lonsdale 1994).