Hi all, I was driving along the highway the other day and noticed that
some tall pine trees have lower branches and others don't. I would
suggest the reason for this is that in some groves of trees the sun
manages to reach the lower branches either because the grove has a
plain on one of its edges or because the upper branches are sparse
enough to allow a sufficient amount of sunlight through to allow the
lower branches to photosynthesize.

One other explanation would be that there are foresters who
intentionally go through and remove the lower growth from the trees so
that the trees don't waste undue energy on maintaining the lower
branches which aren't as capable of producing energy. Would another
possible explanation be simply a difference in the species of the
tree? For instance some trees are just better at maintaining lower
branches with minimal exposure to sunlight.

Thanks for any suggestions for why this phenomenon occurs,
Novice

Novice wrote:
Hi all, I was driving along the highway the other day and noticed that
some tall pine trees have lower branches and others don't. I would
suggest the reason for this is that in some groves of trees the sun
manages to reach the lower branches either because the grove has a
plain on one of its edges or because the upper branches are sparse
enough to allow a sufficient amount of sunlight through to allow the
lower branches to photosynthesize.

One other explanation would be that there are foresters who
intentionally go through and remove the lower growth from the trees so
that the trees don't waste undue energy on maintaining the lower
branches which aren't as capable of producing energy. Would another
possible explanation be simply a difference in the species of the
tree? For instance some trees are just better at maintaining lower
branches with minimal exposure to sunlight.

Thanks for any suggestions for why this phenomenon occurs,
Novice

Both of your ideas are probably right and are complementary as well.

From a molecular biology point of view, the cells in the tree branches
are pre-programmed to die, unless they get signals from the rest of the
tree telling them not to kill themselves. The farther the branch is from
the top of the tree and the less light (at a specific color aka
wavelength), the more likely the branch is to not get the signal to keep
itself from shutting down and cutting itself off from the rest of the plant.

If you're interested in getting really deep into this sort of thing at a
molecular level, try these for search words: P450, senescence,
apoptosis. (It's a very important topic for a lot of reasons.)

Pine trees are a crop just like cabbages. The lower branches are pruned
regularly so that the wood which will be harvested will be straight grained
and therefore fetch a much higher price - simple



Quilljar
Website
http://www.quilljar.btinternet.co.uk/
Do not reply personally, false address

"Quilljar" expounded:

Pine trees are a crop just like cabbages. The lower branches are pruned
regularly so that the wood which will be harvested will be straight grained
and therefore fetch a much higher price - simple

That may be true if you're talking about a tended woodland, but in
this case the OP is talking about pine trees in general. There isn't
a little tree gnome running around the woods trimming branches.

A pine growing out in the open will keep most branches because there's
nothing competing with the branch for sunlight. In a woodland setting
there are always other trees coming up, so the pine puts more effort
into growing taller to stay in the sun. It's as simple as that.
--
Ann, gardening in Zone 6a
South of Boston, Massachusetts
e-mail address is not checked
******************************

Ann wrote:
"Quilljar" expounded:

Pine trees are a crop just like cabbages. The lower branches are
pruned regularly so that the wood which will be harvested will be
straight grained and therefore fetch a much higher price - simple

That may be true if you're talking about a tended woodland, but in
this case the OP is talking about pine trees in general. There isn't
a little tree gnome running around the woods trimming branches.

Well, you may be right Ann, but he didn't actually specify wild woods. In my
experience trees usually belong to somebody, and they get pretty annoyed if
you mess about with them, camping and so on. Mind you, I live in the UK and
our wilderness disappeared sometime around 1066 AD! All our forests are now
tree farms.


Quilly

Dear Novice:

Assuming you are correct in that the trees are pines and not spruce, fir,
larch, redwood, etc., there is a simple explanation for this sort of
observation. Pines are (almost all) shade intolerant: That means they do not
send new growth into areas where the intensity of sunlight is too low to
"justify the investment" in new tissue.

Additionally, some species (such as white pine) are much aggressive
self-pruners than others (e.g. the spruces). Self-pruning is the term we use
for when a tree sheds branches that have died, and in the majority these
branches died due to the low-intensity of sunlight on them as the
surrounding trees grow and shade each other. Trees are much more
compartmentalized as organisms than are animals, and if a particular branch
does respires more energy than it fixes via photosynthesis, the tree 'opts'
to kill and often shed it.

Hope this helps!
ML
--
Mike LaMana, MS, CTE
Consulting Forester & Arborist
Heartwood Consulting Services, LLC
Toms River, NJ
www.HeartwoodConsulting.net



"Novice" wrote in message
om...
Hi all, I was driving along the highway the other day and noticed that
some tall pine trees have lower branches and others don't. I would
suggest the reason for this is that in some groves of trees the sun
manages to reach the lower branches either because the grove has a
plain on one of its edges or because the upper branches are sparse
enough to allow a sufficient amount of sunlight through to allow the
lower branches to photosynthesize.

One other explanation would be that there are foresters who
intentionally go through and remove the lower growth from the trees so
that the trees don't waste undue energy on maintaining the lower
branches which aren't as capable of producing energy. Would another
possible explanation be simply a difference in the species of the
tree? For instance some trees are just better at maintaining lower
branches with minimal exposure to sunlight.

Thanks for any suggestions for why this phenomenon occurs,
Novice

"Quilljar" expounded:

Well, you may be right Ann, but he didn't actually specify wild woods. In my
experience trees usually belong to somebody, and they get pretty annoyed if
you mess about with them, camping and so on. Mind you, I live in the UK and
our wilderness disappeared sometime around 1066 AD! All our forests are now
tree farms.

Oh, well, I guess we're both posting from our differing perspectives.
I've seen your forests, I had a wonderful early morning walk through
what was called the New Forest somewhere down near Torquay (I think
that's where it was). I loved the fact that it was an ancient forest
with that name! What a wonderfully beautiful walk that was......)
--
Ann, gardening in Zone 6a
South of Boston, Massachusetts
e-mail address is not checked
******************************

Oh, well, I guess we're both posting from our differing perspectives.
I've seen your forests, I had a wonderful early morning walk through
what was called the New Forest somewhere down near Torquay (I think
that's where it was). I loved the fact that it was an ancient forest
with that name! What a wonderfully beautiful walk that was......)

I live very near The New Forest, a bit further East than you thought!
So much of it has been cut down (originally to build warships to fight the
French) that it is largely open heathland now. We like to walk there too...


--
Quilly
Website
http://www.quilljar.btinternet.co.uk/
Do not reply personally, false address

"Quilljar" expounded:

I live very near The New Forest, a bit further East than you thought!
So much of it has been cut down (originally to build warships to fight the
French) that it is largely open heathland now. We like to walk there too...

o doubt it is further east, I was on a Mass. Horticulture garden tour,
started at the Chelsea flower show and went east then south then west,
it was a wonderful trip. I could retire and die happily in Cornwall.
You're so lucky, to live in such a gardening country. There's nothing
like that over here.

--
Ann, gardening in Zone 6a
South of Boston, Massachusetts
e-mail address is not checked
******************************