Summer Limb Drop.

i would bet money that

a) the internal structure of a limb goes through the most changes during winter (freezing, thawing, snow/ice weight, high winds)

b) during the growing season, with transpiration resuming the limb is put to an additional test (through higher increases/decreases of water weight)

c) the weight of a limb being in full leaf (summer) makes limb drop more likely

?
 
the rings of horizontal limbs and larger or older limbs generally have thicker rings on the under side.

Late wood and early wood are different animals in that late wood is basically more fibre.

The difference between sapwood and heartwood will be more pronounced especially in diffuse-porous wood of limbs

the movement of water flowing more freely on the underside and in combination with the aforementioned posts is all that I can see. No more no less and no mystery.

gotta run excuse the qucik ramblings of a Horticulturist/Arborist
smile.gif
 
Perhaps a crack from an earlier storm just gets to be too much to handle?

I had a limb drop on a poplar once - no wind.

Examined the limb (plus witnessed an additional event). Seems that the upper portions were damaged and had cracked some time earlier (wood was very slightly discolored). The additional event - 3 years prior a tree company had bounced a top through the attachment point of the limb. We had been working next door and witnest the "areas finest tree service" working through a disasterous removal. It was definitely tree porn, wish I had had a camera.
 
Got the kiddies to school, another rain day for me.

Had a second to reread my post and see it as
scorched earth communications. oh well!

Hidden internal defeciencies are a definite.

When you think about a piece of wood bending to failure it will be the interior failing or fracturing first because it is at the apex of the bend and that would be why there is little to no outward sign of failure. Sapwood being more flexible than heartwood.
Once again back to wet vs dry(er) wood. Flexiblility vs strength, Compression vs tension, protoplast ability to lignify wood, number of sapwood rings( 2 for a given species and upto 12 for others.

upper and lower beam of wood working for and against each other as well.

What are the consistencies observed? most common species, environment( high and dry or flat or low, location on tree,
etc?
 
The only consistent factors are overextension, outside the crown outline, and heavy endweight.

The rest is, and most likely will stay, speculation.

The break most often occurs at the "hot spot" just outside the extended collar. Was tissue Inside previously strained, probably, but thats almost a given at that location

John Goodfellows work on small branch failure imo informs study of SLD
 
I've noticed this on humid summer days, like the day after a heavy rain when the weather is calm and clear, people tell me the limb, "just fell". Many times the limb is fully leafed out with no apparent structural defect such as included bark. Upon closer inspection, there is usually some weak point, such as a past pruning wound, or storm damage, but nothing that compromises the ability for water and nutrients to flow up and back, so the tree looks perfectly OK. A suspicion I have is that there's brown rot fungi working in these weakened areas, breaking down the ligin and thus the strength of the branch. Anyone else see this?

http://en.wikipedia.org/wiki/Wood-decay_fungus
 
ok lets try this. Thanks @JD3000 , @Daniel and @evo for getting me there. Just ramblings:tanguero:
1. Trees photosynthesize/tranpire at higher rates with cloud cover/overcast and high temps
2. CO2 and H20 are being pulled from the wood to facilitate photosynthesis
3. the force created by the movement or loss of CO2( primarily) in the interior of the limb to periphery of said limb, fragments or collapses or alters the wood in such away that it becomes structuarally weak.
Photosynthesis and the movement of CO2 maybe one of the key contributors to Sudden Limb Branch Drop
Transpiration or a water defeciency may still be contributing factor.
CO2 is not readily available from the atmosphere for limb wood photosynthesis and draws CO2 from the interior of the limb.
OK thats all for now, sleep on this see what tomorrow brings:sleep:
 
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Why is photosynthesis greater on an overcast day? You talking about stomates closing at high temps and intense sun to conserve water? Not following you
 
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Eh, ask Daniel first. See what he has to say. I don’t really deal much with SLD in my conifer land in the urban rural interface. More rural than urban. 99% if summer limb failure is wind and defect related.
 
just a fact I read in Journal? Ttrees ability to respond normally ie close stomata, shut down photosynthesis and reduce transpiration is not easy with cloud cover/overcast. Basically trees will dessicate more quickly on an overcast day. Photoradiation is key for stomata to close. A may have been Pirone, not sure or in one of my ecology books. Apple orchard study, not sure where it is.
 
very interesting... FYI evo.. summer limb drop refers to big limbs failing on perfectly still days, generally with NO DEFECTS or decay in the area of failure.. .. it freaks the homeowners out , especially when the limbs land in their hammock.. They pick the phone up and say please come cut my tree down.... Ah ... you should have listened to me when I told you to take some weight off the tips o those big heavy horizontal limbs...
 
Daniel said:
very interesting... FYI evo.. summer limb drop refers to big limbs failing on perfectly still days, generally with NO DEFECTS or decay in the area of failure.. .. it freaks the homeowners out , especially when the limbs land in their hammock.. They pick the phone up and say please come cut my tree down.... Ah ... you should have listened to me when I told you to take some weight off the tips o those big heavy horizontal limbs...
Click to expand...
Oh I had no idea, thanks for teaching me something I already knew.
 
RopeShield said:
just a fact I read in Journal? Ttrees ability to respond normally ie close stomata, shut down photosynthesis and reduce transpiration is not easy with cloud cover/overcast. Basically trees will dessicate more quickly on an overcast day. Photoradiation is key for stomata to close. A may have been Pirone, not sure or in one of my ecology books. Apple orchard study, not sure where it is.
Click to expand...

It seems like one could use trees laden with mistletoe to test that since the mistletoe stomata run more wide open than the tree stomata?
 
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