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<Bill Logan>
posted
A client with compacted soils, owing to recent construction, is experiencing a number of trees with late leaf-out and with much smaller than normal leaves. This leads to me to wonder: What is the physiology of leaf-out? Is it influenced -- both in timing and size -- by the pressure that the vascular system is able to exert? Else, why should leaf-out come later or come small, when soils and roots are damaged?
 
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<Scott Cullen>
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Reply to post by Bill Logan , on May 27, 2002 at 09:35:26:

Really good question. Could we also pose it inversely (?): If a tree with apparent root system compromise (physical damage or soil compaction) does not show late leaf out or reduced leaf size can we infer that vascular pressure is not so compromised?

To refine a little more are there pressure levels that result in various effects? E.G. really low pressure = overall effect; really really low presure = mortaility. Slightly reduced pressure = top die back (can't push fluids that far) but rest OK.

I ask this in the context of the "Remediation of severe root damage" thread 10/01 earlier in this topic.
 
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<Guy>
posted
Reply to post by Bill Logan , on May 27, 2002 at 09:35:26:

Vascular system exerts pressure when roots are working to push fluid upward. That happens when there's enoughwater, air, nutrients available.
this brings up the ISA brochure on Treatment of Construction-Damaged Trees...Radial trenching is in a way counter-intuitive--trenching root zones to help grow new roots?--Horrors!

But the science is sound and the effects are there. I got a copy of the paper from China that helped get the procedure recognized, and it's amazing.
Now before I recoil from the idea, I consider the profound effects of our machines on root systems, then trench away.
 
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<Mark Goodwin>
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Reply to post by Bill Logan , on May 27, 2002 at 09:35:26:

It has been my understanding that root pressure is only one component of vascular system function. Transpiration does most of the work, doesn't it, once the leaves are out?
For late or small leaf out, I would suspect energy deficit, as well as a compromised vascular system.
What occurred during construction? Massive mechanical root damage? Major withholding of irrigation? Change of soil pH? Suffocation of roots? Introduction of disease? How long were the trees stressed by factors related to the construction?
What else may have been going on with the trees before construction? Any pre-existing conditions?
I believe that climatic variations also play a role in determining the timing of leaf emergence. Drought too.
 
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