BS3998:2008 Draft Section 9 - Crown management by pruning

[Amelanchier]

As you are all by now probably aware, there is a draft out for the revised BS3998. Its in a consultation period now but as the document is a bit hefty (and a bit intimidating?) I thought I'd pull some chunks out of it for you all to chew on.

 

Remember, this is the standard that you should be referring to in your quoting and is certainly the standard to which you'll be conditioned to follow with regard to planning and TPO consents. So its worth having a look at what the changes will be!!

 

Case in point Section 9 Crown Management by Pruning and related annexes (my emphasis in bold)

 

9.8.1 General

...NOTE 2 Within the context of crown reduction as opposed to “topping”, the diameter of cuts would

not normally exceed 100 mm.

 

Worth knowing don'tcha think? Is that something you work to already??

 

Annex E.1.3 Severity of pruning

Pruning can be regarded as severe if the total cross-sectional area of all the

cuts is more than one-third of the cross-sectional area of the trunk. As shown in Table E.1,

forty-eight cuts of 50 mm-diameter have the same area as a single 346 mm cut (see also

Figure E.1 concerning reduction of the volume of the crown).

 

So, a useful rule of thumb? Impractical? What do you think?

 

9.8.4 Specifications for crown reduction

The specification for crown reduction should be accurate and clear, so that the desired

result is achieved. To avoid ambiguity, the specified end-result should be stated either

as the tree-height and branch-spread which are to remain, or the average equivalent in

branch length (in metres). End-results should be specified for individual branches if

the growth habit of the tree creates a need for this.

NOTE 1 Specifications for a “percentage reduction” are imprecise and unsatisfactory without

reference to volume, length, height, spread etc. A 30% reduction in crown volume can be considered to be approximately equivalent to a 12% reduction in overall branch length (i.e. radial distance).(See

Figure E.1)

NOTE 2 Specifications for crown reduction which state what will remain are normally used to enable

verification, but, to assist implementation, may be translated into what is to be removed (e.g. length of branch).

 

Therefore, you will no longer be able to recommend just a 20% reduction to BS 3998. Will that affect you? How many people out there quote using percentages? Do you do it to give the climber a bit of flexibility?

 

This is the sort of stuff that will affect your day to day work and believe me thats just a tiny proportion of the changes. To me this looks like a hugely comprehensive document, definatley something that will help UK arb.

 

I'll pull some other points of interest out over the next few days.

[High Scale]

9.8.1 General

...NOTE 2 Within the context of crown reduction as opposed to “topping”, the diameter of cuts would

not normally exceed 100 mm.

 

Worth knowing don'tcha think? Is that something you work to already??

 

Annex E.1.3 Severity of pruning

Pruning can be regarded as severe if the total cross-sectional area of all the

cuts is more than one-third of the cross-sectional area of the trunk. As shown in Table E.1,

forty-eight cuts of 50 mm-diameter have the same area as a single 346 mm cut (see also

Figure E.1 concerning reduction of the volume of the crown).

 

What about re-reduction of a tree? Something I seem to be doing a lot for local authority's.

[Mesterh]

Will the new revised BS3998 be freely available or will we have to pay for it?

 

We use percentages alot but only as a guideline really, 5% being basically a crown clean and 30% being fairly drastic!

 

I'd say the 100mm for reductions being probably about right, but if we start having to go by diameters of branches etc it could get fairly tricky.

Anyhow none of the Arb officers I know couldnt probably be arsed to get up there and have a look anyway

[Yorkshireman]

severe prunning ie not to 1/3rd, has to occur as wind / structural /collision, damage or failure dictates

[Yorkshireman]

i've spent quite some time commenting on this as it effcts all practioners, consultants & TO's for that matter

[Rowan the Bruce]

Thanks for the info Tony, it's exactly what I need at the moment with regards to explaining to a client that he won't get a 30% crown shrinking on his mature Quercus petrea due to the fact that it is a canopy that has reached its limit.i.e. no real pruning points lower than 4 or 5 feet from the tips. There's a 5 day notice on the tree, hollow at the base and attacked by Inonotus dryadeus and a 30% crown reduction recommended by the council, several targets including a house, but a very valuable amenity tree so sensitivity is a must. I'm just starting out on my own and would love to see more of the BS recommendations for tree work, can anyone help? I guess I should buy it really, but getting kit to do the job is top of the list right now.