Soil compaction, remediation and mulching, the rhizosphere

[Tony Croft aka hamadryad]

Taken from the TEP site.... nev wont mind... I hope!

 

PART III

 

A note from Neville Fay, seminar chairman, on some important issues that came out of the discussion session:

 

This seminar has been very well received with numerous requests for it to be repeated. Other requests have been for the theme to be developed to further explore the soil-root-microorganism complexity. There appears to be a real thirst for this level of information and quality for presentation to inform theoretical and practitioner knowledge of tree eco-physiology.

 

A very valuable aspect of seminar III was expressed in the question and answer session.

 

In this an interesting question was raised regarding the use of wood chip mulch; asking for guidance on appropriate treatments for trees where excessive doses of nitrogen have been applied in the past, usually in agricultural settings as a result of direct fertilization or indirect stock fertilization. Related to this question was the risk of introducing pathogens (such as Phytophthora) into the soil through wood mulch application.

 

Olaf Riberiro expressed the view that the presence of lignin and cellulose mulch could enhance the presence of mycorrhizas which benefit indirectly from humic residues. A wood chip medium can enrich the balance of decomposers and symbiotic fungal communities.

 

Alan Rayner concurred with this view and offered some very interesting observations regarding the processes and effects resulting from the laying down of wood chip. He described how basidiomycetes (the most commonly experienced fungal group which includes bracket fungi, mushrooms and puffballs) tend to appear late on in all kind of fungal ecological successional contexts.

 

Basidiomycetes by-and-large remove fungal competitors in the successional process because of the way they handle oxygen. This is influenced by their cell boundary enzyme systems. In this sense the chemical ecology of fungi can be understood largely by the chemistry associated with cell boundaries. Enzymes such as peroxidase and phenoloxydase can cause the release into the surroundings of hydrogen peroxide, which in turn can knock out other organisms. Alan Rayner considered that this was one reason why basidiomycetes replace other fungi late on in all kinds of succession. This he thought would be especially the case in lignin-cellulose rich residues. Basidiomycetes also have a mechanism known as hyphal interference, which links in with these successional processes.

 

In cases where high levels of nitrification have occurred, with potentially detrimental effects on trees, it was argued that as nitrogen pushes up early-phase organisms (such as Pythium and Phytophthora sp.), by adding lingo-cellulose rich residues it could be said that this is likely to encourage basidiomycetes succession with the effect of restoring the balance in the soil.

 

It was also argued that in such circumstances the use of non-composted or part-composted material would seem more beneficial than completely composted material, as this composting process of the wood chip would assist in reducing excess nitrogen from the soil ecology.

 

In answer to the question whether adding lingo-cellulose mulch to soil might adversely affect mycorrhizal communities, Alan Rayner’s view was that this would not be so, particularly in relation to the four main families of trees in temperate and boreal forests which form ectomycorrhizal relationships with basidiomycetes. In the Northern hemisphere ectomycorrhizal relationships are associated with the pines, willows, birches, as well as with beech and oak. As indicated above the application of residues would foster beneficial successional relationships in the micro-ecology of the soil rooting environment. However, different consideration may be needed for species such as sycamore, elm and ash as they have endomycorrhizal relationships, which may even benefit more from nitrogen rich environments.

 

David Lonsdale pointed out that nitrogen- rich root environments also have the effect of including rapid root growth, which can increase susceptibility to infections from early successional species such as phytophthora. It was also pointed out that as a tree ages there is a natural tendency, particularly in the post-mature stage, to increasingly produce saproxylic material, thus beneficially releasing lingo-cellulose content into the soil.

 

The presence of ‘coarse woody debris’ is a feature that might be expected to be found in abundance in old growth forests. However, as in many urban and rural setting, it is common to remove such woody material, then it could be that such ecological processes are being inhibited with increased potential for the pathogenicity of early stage successional organisms. The view was also explored that applying log piles might be even more beneficial than wood chip, as this is more consistent with the gradual breakdown of material and potentially increases the range of beneficial fungal colonizers, consistent with natural forest processes.

 

Nev Fay

[BatiArb]

Thanks Tony, and excelent contribution to this thread.

[sean freeman]

Thankyou for posting the excerpt.

[Tony Croft aka hamadryad]

What i feel is so important about that extract is that the "common sense" of simulating and stimulating the trees "natural nieghbourhood" or environment with arbor ecology principles, something many of us have been trying to promote and use as much as possible for a number of years (Andrew Cowen/Ted Green especialy) is now being academicaly and scietificaly proven.

 

In essence, the moral of the story is that you cant beat "the system" and we have to learn to work WITH the flow instead of against it.

 

king kanute made a mistake many moons ago, he stood defiant, he tried to stem the flow, and yet despite this lesson, we still stand defiant and omnipitent at the ordasity of nature to prove itself always the master of all.

[Tony Croft aka hamadryad]

An interesting little piece, only read the summary so far, but its a worthy contribution to the topic of soil/mulch dynamics.

 

Spatial separation of litter decomposition and mycorrhizal nitrogen uptake in a boreal forest - Lindahl - 2006 - New Phytologist - Wiley Online Library

[Xerxses]

An interesting little piece, only read the summary so far, but its a worthy contribution to the topic of soil/mulch dynamics.

 

Spatial separation of litter decomposition and mycorrhizal nitrogen uptake in a boreal forest - Lindahl - 2006 - New Phytologist - Wiley Online Library

 

Jesus Hama, youre going hardcore....even reading the original paper in Swedish did my head in...

[Tony Croft aka hamadryad]

Jesus Hama, youre going hardcore....even reading the original paper in Swedish did my head in.

 

 

Ive just had another deeper look at the whole piece, wicked stuff!

 

I will take the comment as a compliment:thumbup1: i guess im almost a nerd!

 

[Xerxses]

 

 

Ive just had another deeper look at the whole piece, wicked stuff!

 

I will take the comment as a compliment:thumbup1: i guess im almost a nerd!

 

 

By all means... do! Will have another read too, just a bit heavy at the moment.

 

Nerd? You?!? Its absolutely normal you know...nothing to be ashamed of...