UKTC Archive

Loss of soil strength in dry weather

Subject: Loss of soil strength in dry weather
From: Ben Rose
Date: Aug 09 2018 10:12:35
I recall that this subject was recently discussed on the forum. Well 
yesterday I was called out to look at a large veteran oak that had shifted 
because of soil cracking around the base. Its an old pollard that had lost a 
couple of crown stems and so the crown was lopsided. I'm pretty sure that the 
loss of soil strength caused by the recent dry weather is a major factor 
behind this.

The groundsman noticed that one lower branch was closer to the ground than 
normal, and taking a look at the base there were very large cracks and you 
can see that roots have moved (photo attached). There were lots of cracks in 
the soil, and there were new cracks on the trunk in the tension wood and the 
compression wood. The crown of the tree had a good covering of foliage, 
especially low down and so we carried out an emergency 40% crown reduction. 
It looks like it may have worked because the tree has sat back by 3degrees 
overnight.

We used a clinometer app to measure the angle of the tree's lean yesterday 
and it was 34degrees, and this morning its 31degrees. We marked a point on 
the trunk where we can take repeat measurements from. It's extremely useful 
to know how the tree is behaving in situations like this, I know that the 
tree surgeons (working from a cherry picker) were comforted to know that the 
tree wasn't moving as the day progressed. I recommend that all 
arboriculturists download a free clinometer app on their phones for jobs like 
this, I've attached the sort of output that you get.

Best regards,

Ben








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Attachment: clinometer reading.jpg
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Attachment: soil cracking.jpg
Description: JPEG image