UKTC Archive

Re: Tree Risk Management - Senescence and Rejuvenescence

Subject: Re: Tree Risk Management - Senescence and Rejuvenescence
From: Wayne Tyson
Date: Feb 07 2020 09:34:11
Jon Heuch,

Oh, *that* makes sense. Se la va sans dire! I was having trouble
understanding how one would "rejuvenate" the original tree.

I remember seeing a photo of a man who kept his (several) cows in a corral
within the many aerial roots of a giant ficus in India. Their tendency to
produce aerial roots makes them an excellent candidate for air-layering.
Ficus is one of those genera that tends to buttress its primary scaffold
structure quite well, but in drier climates where the aerial roots don't
form, they have a tendency break (when the weight is enough and moment arm
is long enough).

Wayne

On Thu, Feb 6, 2020 at 5:06 AM Jon Heuch <jh@xxxxxxxx.co.uk> wrote:

Just how does "rejuvenescence" come about in a senescent tree?



Wayne



You have to go back to basic tree physiology and developmental biology. You
will have heard of stem cells and know all about the cambium & other
meristematic tissue.



A whole tree doesn't rejuvenate, (new) parts can however. The challenge for
practical arboriculture is to keep an old tree (ancient, veteran or
whatever) alive by rejuvenation whilst understanding that a declining
structure may make it difficult to keep the whole tree alive. Sometimes
this
is only possible through vegetative propagation or (maybe) via in vitro
tissue culture.



Arborists typically use the term maturity to refer to the whole tree,
without acknowledging that from a physiological point of view parts of the
tree are dead (the heartwood, those dead branches), some may be well
declining (i.e. the decaying & disappearing bits), whilst others may be
rejuvenating. So it's a choice - do you want to use the term "mature" to a
whole organism and its journey through life or as a physiological term?
There is some correlation between the two uses, but there is also
divergence
& room for confusion.



Arborists could learn a bit from practical plant propagators & tree
breeders
who need to rejuvenate old trees to propagate them via cuttings & other
vegetative means. I learnt to air layer old Ficus trees with cow dung and
the correct branch orientation from Nepali famers..there's a lot of
practical experience outside of arboriculture if you know where to find it!



Jon






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