Compartmentalisation of wounds

[Chris at eden]

Another consideration is the different ways in which heartwood or sapwood prevent decay.

 

Heartwood contains phenolic compounds which give it its colour and prevent decay as they are extremely toxic to micro organisms. Example would be oak. Generally only specialist organisms such as chicken of the woods can decay heartwood as they have developed strategies to do so though evolution. If you cut a branch and expose heartwood its defence stays in place so they are resistant to most decay organisms. There are exception obviously.

 

On the other hand trees with only sapwood (e.g. birch) rely on the wood being filled with water to prevent decay. Decay fungi require oxygen to respire so are kept in check while vessels are filled with water. Prune a branch off a birch and the vessels dry out. They can then decay as the defence has gone. In fact, fungi such as Piptoporus are believed to be latent colonisers in that the sit within the water filled vessels in a dormant state waiting for the right conditions. Once the vessels dry the spores can develop.

 

Another good example of sapwood vs. heartwood is in old woodland oaks. If you look at the very old dead branches all that remains is the central core of durable heartwood with the less durable other area of sapwood decayed and fallen away.

[Chris at eden]

I thought of another.

 

Beech has a heavily suberized barrier zone (not all trees do) which makes it very difficult for organisms to cross. One of the problems with using micro drills to investigate is that it breaches the barrier zone and its suberin defence.

 

Timing of pruning. Trees have a reduced phenol index during their dormant season meaning that wound response is minimal during the winter. Tylosis is also temperature dependent and does not occur at very low temperatures. Reaction zones may not form at all in some species at very low temperatures.

 

The list goes on!!!

[Ricbob]

Nobody said trees are clever! its the process thats clever.

 

you could say that everything is simply the conclusion of a sequence of trial and error iterations, does that make a human or any animal or machine for that matter, less clever?

 

 

 

Trees aren't clever!

 

Over a million years of small and large mutations, successful mutations are rewarded by making it to reproductive maturity and pass on the successful genes. Tree speciae adaptations may appear clever but they are really the result of millions and millions of unplanned trial-and-error experiments. Basic Darwinian stuff.

 

It doesn't make trees any less wonderful, but they aint clever. The fast living willow that has offspring with a genetically controlled higher dedication to would compartmentalisation are out-competed compared to their brothers and sisters that genetically put all their energy into fast growth.

 

Killjoy :-(

 

PS willows and the other fast growers are very good compartmentalisers of basal wounds, but not of branch wounds. Compare with lime which is the opposite.

[Ricbob]

Thats interesting, as winter is most recommended as the time to prune, (exceptions withstanding)

 

So are we saying even with the trees reduced defences it still out weighs pruning at other times of the year?

 

ie the affect of loosing photosynthetic mass at a time of need and that pathogens are more prevalent at warmer temps, etc...

 

 

I thought of another.

 

Beech has a heavily suberized barrier zone (not all trees do) which makes it very difficult for organisms to cross. One of the problems with using micro drills to investigate is that it breaches the barrier zone and its suberin defence.

 

Timing of pruning. Trees have a reduced phenol index during their dormant season meaning that wound response is minimal during the winter. Tylosis is also temperature dependent and does not occur at very low temperatures. Reaction zones may not form at all in some species at very low temperatures.

 

The list goes on!!!

[MATTMOSS]

Thats interesting, as winter is most recommended as the time to prune, (exceptions withstanding)

 

So are we saying even with the trees reduced defences it still out weighs pruning at other times of the year?

 

ie the affect of loosing photosynthetic mass at a time of need and that pathogens are more prevalent at warmer temps, etc...

 

Good question that shows your thinking about it. I came up with the same question also.

I think the best way to look at it is in two ways, energy levels and decay probability?

Pruning in winter in most circumstances is better for the tree in terms of not depleting the trees energy levels, which it needs to stay strong and vigorous.

However at this time it is probably the worst time in terms of the trees biological defences are concerned.

This damage can be mitigated by proper pruning practices to some degree,

Pruning to b standard eg branch collars gives the tree the best chance of compartmentalising the forthcoming dysfunction and possible decay.

Most sp of trees biological defence mechanisms are inactive around zero degrees as Chris says so the tree cannot begin to respond to damage until warmer temperatures and the onset of growth begins.

Personally I think every scenario - species, tempreture, season, tree vitality can be analysed to death to come up with the best time to carry out a certain procedure on a certain tree for the best results or the least Ill effects.

The best advice is to prune trees when they're young and vigourous and can overcome most damage, when they become more mature it can be very damaging. The right tree for the right place.

 

Err what was the question

[Chris at eden]

Pruning in the winter is a traditional approach but I'm not convinced its correct one. Most of the common decay fungi fruit in the autumn meaning that spores are at an all-time low during the summer months. There are exceptions. If it’s hot and dry that doesn't favour fungal development either. And the trees are actively growing meaning they can perform CODIT as they have not only the potential energy within their tissues but also an abundant re-supply of kinetic energy produced through photosynthesis.

 

The production of reaction zones through tylosis, etc requires energy, something that deciduous trees don’t make in the winter. If they are expected to draw on their potential/stored energy through the winter it would reduce the mass/energy ratio which is needed to kick start growth in the spring. That wouldn’t be a great survival strategy hence they do nowt and start to react only when growth kicks in next year. I don’t really think it makes a huge amount of difference, just small margins really. How many tree surgeons only prune for 6 months of the year!

 

The Askanazy curve is also accepted when people say don’t prune before the leaves come out. This is based on Askanazy testing starch levels in trees before leaf burst when he found them to be low. Problem is, he only checked cherry trees. It’s not surprising their energy is low as they flower before they leaf. That uses up energy which cannot be replaced before the leaves are out. Yet still people advise this. Again how many trees have you pruned before the leaves come out and what was the effect? Not much in my experience.

[MATTMOSS]

Pruning in the winter is a traditional approach but I'm not convinced its correct one. Most of the common decay fungi fruit in the autumn meaning that spores are at an all-time low during the summer months. There are exceptions. If it’s hot and dry that doesn't favour fungal development either. And the trees are actively growing meaning they can perform CODIT as they have not only the potential energy within their tissues but also an abundant re-supply of kinetic energy produced through photosynthesis.

 

The production of reaction zones through tylosis, etc requires energy, something that deciduous trees don’t make in the winter. If they are expected to draw on their potential/stored energy through the winter it would reduce the mass/energy ratio which is needed to kick start growth in the spring. That wouldn’t be a great survival strategy hence they do nowt and start to react only when growth kicks in next year. I don’t really think it makes a huge amount of difference, just small margins really. How many tree surgeons only prune for 6 months of the year!

 

The Askanazy curve is also accepted when people say don’t prune before the leaves come out. This is based on Askanazy testing starch levels in trees before leaf burst when he found them to be low. Problem is, he only checked cherry trees. It’s not surprising their energy is low as they flower before they leaf. That uses up energy which cannot be replaced before the leaves are out. Yet still people advise this. Again how many trees have you pruned before the leaves come out and what was the effect? Not much in my experience.

 

I agree

[Gary Prentice]

Hasn't the Askanazy curve been dis-credited/debunked, at least to some extent.?

[Gary Prentice]

Most sp of trees biological defence mechanisms are inactive around zero degrees as Chris says so the tree cannot begin to respond to damage until warmer temperatures and the onset of growth begins.

 

 

Err what was the question

 

But fungal growth also stops around the same temperature, although it starts at lower temperatures than the trees active growth phase does.

[MATTMOSS]

Hasn't the Askanazy curve been dis-credited/debunked, at least to some extent.?

 

There has definitely been an article about it somewhere discrediting it for the reasons Chris mentions above. Maybe an aa journal?