Growth rings in trees...

[Externet]

Hello all.

 

A sawed off section of a tree shows the seasonal rings, age, and some environmental characteristics, but my question is about growth alone; the addition of material to the trunk. Is the younger material at the center or at the bark ?

 

Or, in other words, the diameter of a tree increases as new wood cells form at the core and migrate outward or the new cells accumulate under the bark ?

[John Cuthber]

The new growth happens just under the bark.

[YT2095]

and interestingly there is very little Longitude growth, the Myth that you carve your name in a tree and then wait 20 years to see it 20 foot higher is False

maybe a foot or so max.

but certainly expanded lateraly.

[Glider]

Hello all.

 

A sawed off section of a tree shows the seasonal rings, age, and some environmental characteristics, but my question is about growth alone; the addition of material to the trunk. Is the younger material at the center or at the bark ?

 

Or, in other words, the diameter of a tree increases as new wood cells form at the core and migrate outward or the new cells accumulate under the bark ?

New growth comes from the cambium. This is a layer of living cells under the bark. Cells of the cambium layer differentiate into either xylem (the inside layer) that conducts water and nutrients up from the roots, or phloem (the outside layer) that conducts sugar rich sap down from the leaves.

 

The xylem lignifies over time and becomes heart wood (i.e. the 'timber') which is dead (although the tubules will continue to move water for a time) and provides only structural support for the tree. The phloem also lignifies, but this becomes bark and is usually shed (depending on the species).

 

So, imagine a tree like a skeleton of wood, covered by a thin glove (one or two cells thick) of living tissue that constantly divides into either new wood or bark. So, as YT says, the trunk of a tree will only ever increase in girth, never in height (that's the function of new shoots at the growing tips), so a scar will never move up the tree over time, not even a foot.

[foodchain]

Biologic activity is directly tied to environmental function. So change in environment will register on the organism or population of. Such as lacking certain nutrients can make you more prone for becoming sick. This is the same with plants, with a great deal of species a simple way to see this is to deny light or fry the soil with some composition of elements. Cellular activity is also very neat, you have a clock that is a cluster of clocks so to speak. In that many different processes can be occurring at the same time and you have lots of communication. Cells make up organisms, so in essence the cell physiology and function as pointed out is what leads to more noticeable characteristics like bark or leaves.

[Externet]

Excellent explanation; thanks, Glider.

 

This bring more questions; the core of the trunk being dead still functions 'pumping' nutrients to the branch tips ? Interesting.

And the only few live cells on the trunk are just under the bark; would that be a reason that a tree mostly dies on a forest fire, as there is high exposure to flames ?

And what about the roots, is there a dead portion there too, and the outer layers are the only ones extracting nutrients ?

If so, at the transition from roots to trunk, there is nutrients ducting connection from the roots exterior to the trunk center ?

 

The trunk center 'pumps' vertically and the body 'pumps' horizontally towards the live cells ?

 

It has to be a very interesting mechanism if performed by dead tissue. Capillarity related ?

[SkepticLance]

As glider said, the transport of nutrients, water and minerals is in phloem and xylem tissues right next to the cambium. In other words, living tissue just under the bark.

 

The centre dead tissue is to provide strenth and support only.

 

And yes. The tree dies if the outside living tissue is destroyed, either by fire or by ring barking.

[stevo247]

I had a guy with a backhoe help me clear out some brush on my property and he put a nasty scrape on the side of a large beautiful tree. Is there a way to treat something like that to promote healing?

[Glider]

Excellent explanation; thanks, Glider.

 

This bring more questions; the core of the trunk being dead still functions 'pumping' nutrients to the branch tips ? Interesting.

Not quite. The core of the trunk is fully lignified and provides support only. The layer of xylem under the cambium is technically dead, but the tubules continue to transport water. The cellulose cell walls of these vascular cells are reinforced with lignin and eventually lose the capacity for transport as they become heart wood.

 

And the only few live cells on the trunk are just under the bark; would that be a reason that a tree mostly dies on a forest fire, as there is high exposure to flames ?

Yes. Anything that interupts the flow of water and nutrients to the canopy will kill the tree. However, it is possible to ring-bark a tree without killing it, if you're careful. If you remove the bark from around the trunk and scrape away the cambium only (i.e. do not damage the xylem), water and nutirents continue to be transported to the canopy and the tree will survive.

 

If you keep the wound moist, the edge of the cambium layer at the top of the ring will swell, forming a callus and then begin to form new roots. These will be fed by sap from the phloem until they are mature enough to begin functioning to support the tree. This is a technique (often used in horticulture and bonsai) called air layering.

 

And what about the roots, is there a dead portion there too, and the outer layers are the only ones extracting nutrients ?

Yes, the same principle applies to the roots. In most trees, however long the roots are (and in some, they can be hundreds of feet long), it's only the last ~1 - 2cm that are feeding the tree. As roots grow from the tip, they move through the soil searching out nutrients. The root behind the tip lignifies and turns brown and loses it's ability to transport water and nutrients across its membranes. Brown roots just anchor the tree.

 

At the white growing tip, using a magnifying glass you will see a fine halo of root hairs. This increases the surface area at the tip and it's this area of membrane that sucks up water and disolved salts and minerals.

 

In the wild, the roots can become so long that the transport of water and nutrients becomes difficult and the tree eventually dies. In bonsai, the roots are regularly pruned as long anchor roots are unnecessary and the tree puts out lots of new fine feeder roots. So rootpruning rejuvinates the tree and will significantly extend its life. For example, the valley larch has a life expectancly of 50-60 years in the wild. As bonsai, there are specimens over 200 years old.

 

If so, at the transition from roots to trunk, there is nutrients ducting connection from the roots exterior to the trunk center ?

No. The cambium layer, xylem and phloem are the outermost layers of both the trunk and the roots. Again, think of these layers like a glove, covering the whole tree just under the bark.

 

The trunk center 'pumps' vertically and the body 'pumps' horizontally towards the live cells ?

No. There is horizontal movement between tubules, but only in the xylem layer. The middle of the trunk is fully lignified wood and does not transport anything.

 

Think of the rings you mentioned in your first post. The lighter (thicker) rings are what the tree develops during its growing season. The darker (thinner) rings are what the tree put on as it enters its dormant period.

 

Very basically, the white rings are the xylem layer for each year. In the spring, the trunk thickens as it forms a new xylem. The cell walls of the xylem tubules are reinforced by lignin over the growing season. At the end of the season, the tree withdraws sugars and other nutirients from the leaves for storage in the trunk and roots (giving a second perios of trunk swelling).

 

The tree will use these stored nutrints to kick off new growth the following spring, when it will begin to develop a new xylem layer. The old one will fully lignify and become wood.

 

 

It has to be a very interesting mechanism if performed by dead tissue. Capillarity related ?

Yes. There are two main forces pushing the transport of water and nutrients from the roots to the canopy. One is osmosis, the other is transpiration. At the roots, the contents of cells at the root tips contain higher concentrations of sugars, minerals etc. than the surrounding water, so water and disolved nutrients enter the root cells by osmosis. This is why overfeeding kills plants. The concentration of disolved salts becomes higher in the soil than in the root cells and so reverse osmosis happens, pulling water from the roots, killing the tree.

 

Capillary action helps transport the water through the tree, but also, the leaves are losing water through transpiration and this loss sucks water up from the roots. This action is so powerful that in some trees in the spring, if you puncture the xylem layer with a spike, you can hear hissing as air is sucked into the wound.

 

I had a guy with a backhoe help me clear out some brush on my property and he put a nasty scrape on the side of a large beautiful tree. Is there a way to treat something like that to promote healing?

It depends on the size and depth of the wound. In bonsai, you can buy cut paste (made by Japanese suppliers) to place over wounds from branch removal. It seals the wound and keeps the cambium moist at the point of the wound which (they say) promotes the formation of a neat callus.

 

The tree will naturally form a callus anyway, and this will close on its own over time. Personally, I'm not sure of the value of cut paste, although I use it myself. The calluses that form under the cut paste do seem to be smoother and neater than those that form in open air, but this is just my anecdotal evidence.

 

 

My own suggestion would be to make sure the edges of the wound are clean (i.e. not ragged). Take a (very) sharp knife and clean up the edges of the wound and the surface of the wood within the wound. You want the surface of the wood to be very slightly concave so as the callus forms and grows inwards, it leaves no unsightly swelling, but heals flush with the rest of the trunk. You also want to prevent any rot beginning in the bare area of wood.

 

You should notice the layer under the bark at the edges of the wound begin to swell and move inwards within a season or two. Over time, this callus will completely cover the wound. How long it takes depends on the size of the wound and the species of tree. If you want to speed up the process, you could very carefully cut into the callus each year. This will encourage it to grow more rapidly.

[iNow]

Mon Dieux! Glider is the tree whisperer!

 

You're a good teacher, man. That was amazing.

[Externet]

Yes, superb teaching ability together with knowledge, rare to find both in a person!

Miguel

[Glider]

Awww shucks, you guys