oak tree tarmaced around base

[Fungus]

Absolutely true oxygen and the presence of pore space (macro and micro very very important...hence the relevance of having some idea of how the subgrade has been changed. Not all pavements are formed on the same foundation..(I know you know this).

Your point about the mycorrhizal fungi needing 20 % more than fine tree roots and root hairs is something I have not heard before (certainly not quantified like that) are there any papers you can think of that make mention of this please, I would certainly like to increase the weight of evidence presented in certain real situations where trees are threatened by such construction.

 

Sean,

Among mycologists, it's a well known and documented fact. One of my Dutch colleagues published it in a 1996 paper on the - on the long run - non-sense of commercial mycorrhizal inoculates after critically reviewing 200.000 articles on the subject of introducing mycorrhizae to the roots of nursery and new (re)planted trees.

[David Humphries]

David,

Wouldn't the tarmac after same time be clotted with and compacted by sand, salt and other fine materials and loose it's porous and rain seeping in & through character ?

 

Gerrit,

 

my general comment is based on the partial facts offered.

 

"Apparant good health" was proferred, seemingly insinuating a tree that has adequate water uptake.

 

Without seeing the specific environment we can't really comment on positive or negative porosity.

 

I just stated really that Tarmac is porpous.

 

You make a very valid and debate friendly point though

 

.

[Le Sanglier]

I do not usually follow the science stuff but this has always puzzled me, I was hoping for some definitive answers, strangely no one actually has one, or have I missed something? I do not really buy the porus tarmac theory, surely 99.9 percent of the water runs off.

So denied of a significant proportion of its water supply many oaks I have seen seem to survive without apparent problems. I do not know how, and evidently I am not alone.

One crazy nonsense that occured to me was the roots go down closer to the water table (or something!) probably nonsense but I had to offer an idea no matter how crackpot.

[Paul Barton]

No doubt that under Tarmac roots will travel further in search of moisture. Street trees under Tarmac will send out roots in to nearby gardens and verges. They will also cling to the undersides of Tarmac as moisture produced by condensation can be found there.

 

All that said, I also am amazed that trees manage to survive in such horrendous conditions!

[Fungus]

One crazy nonsense that occured to me was the roots go down closer to the water table (or something!) probably nonsense but I had to offer an idea no matter how crackpot.

 

Apart from Alnus, and less effectively Salix and Populus, which (can) have an ectomycorrhizal pioneer species of the genus Alnicola (= Naucoria) attached to their under water roots, that can live under anaerobic circumstances, because they get their oxygen delivered through/by the tree roots, all other tree species associating with ectomycorrhizal symbionts have species of macrofungi attached to their roots that drown and die when they reach as far as or further than the water table.

And superficially rooting tree species such as Fagus have water avoiding roots with too long or permanently under water intolerant ectomycorrhizal symbionts attached to them.

[Le Sanglier]

Apart from Alnus, and less effectively Salix and Populus, which (can) have an ectomycorrhizal pioneer species of the genus Alnicola (= Naucoria) attached to their under water roots, that can live under anaerobic circumstances, because they get their oxygen delivered through/by the tree roots, all other tree species associating with ectomycorrhizal symbionts have species of macrofungi attached to their roots that drown and die when they reach as far as or further than the water table.

And superficially rooting tree species such as Fagus have water avoiding roots with too long or permanently under water intolerant ectomycorrhizal symbionts attached to them.

 

ok thanks, understood....just!

[Fungus]

1. No doubt that under Tarmac roots will travel further in search of moisture. Street trees under Tarmac will send out roots in to nearby gardens and verges.

2. They will also cling to the undersides of Tarmac as moisture produced by condensation can be found there.

 

1. In The Netherlands, we had two cases, one of a root of Quercus robur and one of a root of a Tilia, send out for over 25 metres under tarmac into a garden and then below ground level penetrating the wall of a cellar, which once inside had Xerocomus (= Boletus) chrysenteron fruiting from the root's tip.

2. Only tree species, such as Acer, associated with endomycorrhizal microfungi are capable of doing that, because there is enough moisture from condensation and more important, enough oxygen present to "support" the mycorrhizae on/inside the fine roots, which do not need to fruit with FB's above ground level to spread their spores.

Edited November 5, 2011 by Fungus

[Pat Ferrett]

Tarmac is porus and flexibable and I think the saying "Grass doesnt grow on a busy road" might have a relevence to this topic, even pedestrians walking on Tarmac will stop weeds growing through but left un touched it will soon start to sprout weeds from the sub base.

The bigger issue is compaction from the traffic either motor or human using said tarmac

[Matthew Storrs]

Well that seems to make sense, i did not realize tarmac was porous. I still think it should be a regulation not to tarmac the trunk though:thumbdown:

[Le Sanglier]

Just checked on google and it is not porous. do puddles on badly laid roads soak away?