What does tree pruning do to the roots?

[daltontrees]

Interesting article, Gimmer, thanks for making it available. There is something odd about the logic that I can't quite put my finger on. It may come to me though. Maybe being in the not-so-sunny west of Scotland makes it impossible for me to imagine Soil Moisture Deficiency.

[daltontrees]

The authors of the article that Gimmer posted suggest that pruning has no long term effect on soil moisture depletion because the roots remasin unaffected by pruning. But surely if you reduce the crown repeatedly and over a long period there will be a net depletion of nutrients to the roots and they will not be able to (or need to) maintain themselves at their full extent and there will be dieback just as a crown dies back if it is deprived of water and nutrients? To say otherwise is to say that a root network once in place is indestructible. Fair enough, roots are not tested by weather, insects, mammals, fungi, bacteria (and tree surgeons) the same way as branches are so wastage will be slow but it MUST happen eventually?

[educated arborist]

any 1 out there into their bonsi? i'm not but a good friend is & he has to prune their roots regularly as the canopy pruning does not prevent them from growing!

 

as for mature trees a severe reduction may inhibit root growth but they will not die back. As for subsidence IT IS NOT caused by roots, their size or their growth but by their moisture uptake on a shrinkable soil. a harsh reduction will often lead to an increased water uptake not reduce it as previously thought.

[Bundle 2]

The daft thing about this and (imo ) the whole "whats wrong with pollarding " argument (as it is somehow related by the repeated pruning that such a strategy entails) By pruning out canopy, water uptake can be prevented and so swd (soil water deficit) reduced/halted.

I think Im right in saying tho' that the resulting regrowth results in increased water uptake as the tree scrambles to mobilise resources... leading to, you guessed it an increased water deficit. The problem stems from, as has rightly been said, the soil environment (structure) and building foundations.

Drought, perhaps experienced in conjunction for the first time with data as it was available, in the 70's led to shrinking soils on clay and problems related to building stability. Its not a tree problem.Its a building issue. Insurers forcing our hand.(Money, mortgage, insurance) Oh and the media machine doing what it does best...bullshitting us!!!

[renewablejohn]

Not quite bonsai but I used to hire out christmas trees with live roots. We used to root prune every year to maintain dwarf growing character and keep trees compact. Every 3 years we would then transplant into a larger pot increase by 5 ltrs at a time upto 25 ltr pot than after that plant out in woodland (approx 15 yrs old 12-15 foot tall) If grown direct in the ground same tree would be in excess of 30 foot so bonsai did work.

 

Mainly Norwegian Spruce and Siberian spruce but also experimented with Noble Fir Frasier Fir Korean Fir Picea konica Nordman Spruce

[Bundle 2]

According to some nursery growers, the yanks are starting to see the results of neglecting root development at the nursery stage...as a result of "container" grown stock that is allowed to get too big fir it's pot!!

If you think about it, this could be mechanical failure as a timebomb ..and in amenity planting this could lead to damage, death and loss?

[Frimsley]

There seem to be slightly different issues coming up here. Pruning the crown is unlikely to cause roots to dieback - the tree has invested energy in creating those roots, why would it kill them off now? But it probably will reduce the rate of growth of roots - there is no need to build up such an extensive network of roots for a smaller crown and there are fewer sugars available for the job because of less photosynthesis.

 

The OCA paper is not about root growth, it's about moisture use. A tree can have a lot of roots and still not use much water. The two are not directly related, although it would be reasonable to assume a tree with few roots isn't going to be able to use much water. I'm not clear what the context of the question is...

[Bundle 2]

In a nutshell....the question is simple enough...Its finding an empirical answer that has so far eluded us.

Perhaps its possible to extrapolate from a the theory that trees will maintain a root:shoot ratio? Apparently it is not as simple as this.

Arborist News- just got my copy Vol18(No6) Dec 2009 Slightly off topic but exposes the way roots are affected by arboreal practices

*(pages 35-39)

[Bundle 2]

". Pruning the crown is unlikely to cause roots to dieback - the tree has invested energy in creating those roots"

I would guess that it may be affected in different ways depending on age class, species and environmental factors. I can perceive of scientific processes that are a part of a trees biology/physiology that would perhaps not make it such a clear cut issue....

[patrickosborne]

Can I throw something else into the melting pot.

Are we wrong then in view of the above facts to remove a large tree over two seasons when on shrinkable clay soil to reduce the possiblilty of any adverse movement?

Should I now reccommend complete removal in one go?