Collybia fusipes

[David oakman]

I was talking about this yesterday, our timber buyer came to look at some large oak trunks i have in the park. The thing is in this country no trees are grown as a crop they are all grown for amenity,treescape. when my oaks die and are felled they are worth not much but if they had been felled at 150-200 years old you would have good timber worth good money. But timber now comes from europe cheap he wa telling me he buys all his oak from france good wood and cheap.

[Bundle 2]

It is very hard indeed to play the wood farmer in the uk these days I'm afraid....The only oak farmer I know sources all stock from France...It seems to be a capacity thing where competition is fierce.the key must be in finding a niche for the wood production...rebranding a product so restructuring its comparative value....?

[BatiArb]

Reading between the lines here abit I got to thinking how many times the trees' roots must have to have been affected by mechanical intervention....

At least once when the road was put down.

This can be said to have affected the bulk soil and rhizosphere then.....?

If the otherside is a field then I can hazard a guess that the top 600mm of soil will have been disturbed on numerous occasions.

Much like the way a trees physiological patterns can evolve during a lifespan ie, pollarding regularly, perhaps the individual becomes able to live with aggressive intrusions that alter soilroot environments??

 

QUOTE]

 

 

 

Now this thread is going in an interesting direction….

 

The whole idea of root age, growth and replacement is something I have given quite a bit of thought to over the last year or so. Not lease because I have had an opportunity to look at a lot of trees using the AirSpade to remove soil from around their roots and buttresses.

 

As such I am beginning to realise how much we have to learn about the growth processes of the tree’s root system. When you go to look in books, and I have been through quite a few now (even some very recent publications), it becomes clear that the information is not available. And more to the point, what is illustrated within the books is frequently completely wrong……baring very little resemblance to real life.

 

The following explanation is based on my experience of predominantly broadleaf trees that I have seen exposed due to root buttress investigations with the AirSpade (mainly mature trees) or of windblown stumps (a mixture of ages) that I have inspected to determine reasons for failure or simply out of personal interest.

 

When the tree is young there is a tendency for it to have what we call a ‘tap root’ which enables it to stabilise itself very quickly within the soil and counteract the growth of the stem above ground. From this tap root growing vertically down into the ground are generated horizontal ‘lateral’ roots that go off in what ever soil horizon is easiest (and therefore at what ever level/depth) to draw water and mineral nutrients for the establishing tree.

 

As the lateral root system spreads out, there becomes less requirement for it to be deep in the soil and the emphasis upon the lower level roots appears to reduced, which means in tree terms that they get less carbohydrates from the leaf canopy above ground. The preferential growth of the root system appears to be dictated by the trees requirements for stability within the soil verses the need to absorb water and mineral nutrients. As such the proactive growth of roots will be influenced by:

 

• a structural load that it has to work against, usually wind loadings exerted on the tree above ground;

• the availability of water or mineral nutrients within the soil where it is growing;

• or both of the above.

 

In many broadleaf trees, as the tree matures more and more of the structural loading is absorbed by the surface roots that are directly connected to the buttresses at the base of the trunk. The surface rooting system also frequently has access to good soil resources such as the organic horizon and rain water runoff within the trees canopy drip zone.

 

Now as the tree feeds the surface roots, associated with its buttresses, with a preferential supply of carbohydrates the natural transport link between the tree above ground and the lower root system slowly becomes less and less. Effectively the tree starts to factor the lower tap root system out of the equation, and these deep roots progressively die as they are no longer directly linked to the supply of carbohydrates from the crown canopy.

 

In maturity, when a tree has developed a central ‘heartwood’, ripe-wood’ or ‘false heartwood’ where the central core of the trunk consists of predominantly dead cells, the roots associated with these areas are also dead and dysfunctional, and therefore become susceptible to decay by fungi such as Meripilus and Grifola (see discussion on other threads), which are frequently associated with the decomposition of the old root system.

 

Now the interesting thing about the root system of mature trees is that there is a continual succession of root development, dominance, suppression and succession. This happens due to the same factors as described above depending on how the structural loads are exerted through the root system and the availability of soil resources.

 

The roots of a mature tree, which has lost its functional ‘tap’ root, can only be as old as the ‘sapwood’ in the trunk. This is an interesting fact that takes some thought to understand so take some time with this. It also helps if you can cut up a stump and take a section of buttress off, so I have included a couple of photographs below. The growth of buttresses is all on the upper side, with all the old wood or historic root on the bottom. This is the area of transition where the vascular system of the trunk transfers through the buttresses into the main root spread below ground.

 

This means that the root system of a mature tree can only be as old as the functional sapwood within the trunk, and in tree species that create a heartwood by impregnating cells with chemicals, this age can be limited to between 20-30 years and is rarely more than 40, particularly in species such as oak.

 

Going back to the oak tree we are currently discussing as a case study, it has already been indicated that there is likely to have been considerable changes in the rooting environment of this tree over the 100(s) or so years of its live, so to find that there is death, dysfunction and decay within its root system is not a surprise, because this is a natural part of the cycle described above.

 

When it comes to inspecting such trees our job is to explore around all the buttresses to work out which ones are dominant (from a structural and soil resource perspective) and which ones have been superseded and therefore subject to decay, so we can then make an informed judgment as to whether it has sufficient roots to survive.

 

Unfortunately we do not have any research to tell us what volume of roots a mature tree needs to survive, or how many buttresses it could lose before it becomes unstable. Having said that though, this is so much down to the circumstances of the trees growing context, it probably would not be possible to apply it anyway.

 

It is a sad and frustrating fact of our arboricultural ignorance that we do not have an adequate understanding of tree root systems generally, let alone deciding when root loss has reached a stage that it has compromised the trees functional growth, or structural stability. So it comes down to experience again and observational learning out in the field.

 

The identification of Collybia at the base of this oak tree has told us one thing, that it has some dead roots, and considering its age and stage or maturity, this is not an unusual situation. What needs to be determined is the number and health of the functional roots that it still has. This information can then be combined with a VTA of the tree above ground with consideration to the context of its exposure to wind loads combined with an assessment of local targets, and an informed judgment can be made as to whether it is safe to leave it standing or whether it needs other work such as a crown reduction.

 

 

 

As described above the two photographs below are both of sections through buttresses, the first is a primary root on a mature tree with all the growth on the top, while the second is a secondary root cut off adjacent to a buttress where the is some consentric growth on the underside, but it illustrates how much biase there is towards the growth on top.

[Will Hinchliffe]

The Longleat estate (who own the tree) still have there own forestry department and seem to be able to turn out some nice timber. Last year we had a blitz on their roadside trees and a lot of oaks came down. A lot of the timber went to the big gas pipe line that they ran through Wales. I think in certain places they were laying the pipe on huge oak bearers. If it comes down I am sure it will get used.

[Will Hinchliffe]

Do active roots contain a proportion of dysfunctional wood ?

[Bundle 2]

This would depend I think Im right in saying on the species and age of the roots in question...if you mean "should they?" This is because sapwood is converted to heartwood ( whu) at varying timescales related to species....oak is suggested 20-30 yrs...not a very concise answer but to a complex question in some ways.....?

And seeings as how I've piped up again already when I just know I'd be better off reading and digesting at this point....

Are you suggesting that the mechanical models popularized by Mattheck , Smiley & Coder re stabilty are incompatible with assessment or are there other issues to do with root function/fungal lifecycles that render the models unreliable?

Tim.

[Dean Lofthouse]

The growth of buttresses is all on the upper side, with all the old wood or historic root on the bottom. This is the area of transition where the vascular system of the trunk transfers through the buttresses into the main root spread below ground.

 

This means that the root system of a mature tree can only be as old as the functional sapwood within the trunk, and in tree species that create a heartwood by impregnating cells with chemicals, this age can be limited to between 20-30 years and is rarely more than 40, particularly in species such as oak.

 

 

As described above the two photographs below are both of sections through buttresses, the first is a primary root on a mature tree with all the growth on the top, while the second is a secondary root cut off adjacent to a buttress where the is some consentric growth on the underside, but it illustrates how much biase there is towards the growth on top.

 

Am I misreading this or are you saying that concentric growth (in the root system) is because of bias feeding the upper part of the root system, which is where most of the soil nutrients are found and not because of structural loading forces as would be found in a cross section of a lateral branch.

 

As I understand it, concentric growth above or below ground is because of forces exerted and adaptive growth to counter those forces and not to do with bias feeding

[Bundle 2]

Am I misreading this or are you saying that concentric growth (in the root system) is because of bias feeding the upper part of the root system, which is where most of the soil nutrients are found and not because of structural loading forces as would be found in a cross section of a lateral branch.

 

As I understand it, concentric growth above or below ground is because of forces exerted and adaptive growth to counter those forces and not to do with bias feeding

Yeah...I have issue with this concept also...believing as I did that forces acting against cell division in quite a very local dynamic were responsible for the asymmetric coss section associated with roots.....

Additionally however, looking at the diagrammatic profiles offered by Andrew , I cant see the system beyond a certain point. Shigo tells us ( bless him) that the "rams horns" as he coined them, rarely grow together...a compression fork( fork is not the right word here) is then formed....I also dont believe the buttress can be as strong once the transverse section has become shallow in the way suggested....

These processes are undoubtedly observable in tree root systems but remain something of a contradiction in terms.....except I suppose that the footprint is enlarged and as far as the root profiles continue, there is no real change....renewal....! ( Also replacement as the tap root is no longer active or present presumably)

But contradictions appear elsewhere also...the buttress, as it becomes the flare, these too can become eccentric and no new wood is formed successionally between them.....curious.

[BatiArb]

Am I misreading this or are you saying that concentric growth (in the root system) is because of bias feeding the upper part of the root system, which is where most of the soil nutrients are found and not because of structural loading forces as would be found in a cross section of a lateral branch.

 

As I understand it, concentric growth above or below ground is because of forces exerted and adaptive growth to counter those forces and not to do with bias feeding[/quote

 

 

 

You are right in both respects, because it depends where in the root system you are referring to.

 

In the buttresses all the growth is on top regardless of stimulus, because this is to do with the transition from being sapwood in the tree to being a root in the ground.

 

It is also true to say that all the load expressed onto the buttress is on the upper side, and loaded buttresses do appear to get bigger in size to cope with such loads.

 

As you follow the root into the ground and take further cross sections, the growth becomes bias on both upper and lower sides of the root, and the I beam form appears. This is likely due to the fact that loads are expressed through such roots as the tree rocks in the ground and the root section in question is loaded up and down respectively.

 

As you get further away from the trunk the roots become loaded more in the longitudinal direction, because the rocking motion of the trunk is expressed more in a pulling force on the roots further away. This means that there appears to be no bias in growth top of bottom, although such roots can be loaded side to side as well.

 

I have attached a couple more cross sections for consideration, one in which the loads are more evenly spread top and bottom, and this root was a metre or so form the trunk, and the other is still loaded more on top. I have also included some illustrations from Claus Mattheck, whcih as ever really need to explanaiton. Respect....

[Will Hinchliffe]

I've just about exhausted all the reading material I have on root physiology. Very little is written in botanical textbooks about secondary growth of roots.

 

I never really picked up on the concept of roots living for relatively short periods of time before.

 

Their seems to be a real gap in the literature when it comes to the responses of the root system to fungal decay.

 

From the last of Matteheks diagrams in the above post it seems like he is saying that decay on the underside of the buttresses would not greatly influence the likelihood of the buttress failing as the majority of the loading is on the outside.