North American Timber/Forestry Forestation/Plantations Investments:
who invests in re-forestation? What are returns on investments,
typical investment amount, investment duration? Is there a secondary
market for buying/selling forests?

I think "tree farming" is the accepted general term for what you are
asking about.
This site may be of interest to you:

  http://www.treefarmsystem.org/cms/pages/20_5.html

and also these since they talk about the financial side:

http://www2.ctahr.hawaii.edu/oc/freepubs/pdf/RM-9.pdf
http://www.cfr.msstate.edu/fwrc/forestry/investments.htm
http://www.ces.ncsu.edu/nreos/forest/economicspubs.htm

Here is a rather long history of forestry:

http://www.findarticles.com/p/articles/mi_qa3854/is_200401/ai_n9393934

Who invests in reforestation?  
The forest owner.  There may be government subsidies, directly or
through supplying seedlings.  (The US government is the major forest
owner and generally considered a poor manager thereof.)
What are returns on investments?  
These can vary greatly depending on the type of trees planted and the
use of the timber.  Hardwoods generally grow slower than softwoods
(pines) and are harvested after many years, a return realized by the
next generation.
Softwoods in a favorable climate can be harvested sooner, especially
if they are going to be used to make paper, since the actual size of
the trees is then unimportant.  Foresters calculate the volume growth
(volume of wood) which is generally greater for young trees, so for
this use, waiting for trees to grow even larger becomes inefficent,
whereas if the trees will be used for lumber, the situation is, of
course, different.
Typical investment amount?
That would have to be based on per acre, but "natural reforestation"
is also used:  leaving good individual trees standing to reseed the
surrounding area.
That does not cost anything (except for foregoing what those trees
would bring), but leaving the job to nature adds a year or two or
three to the project.
A secondary market for buying/selling forests?
"Secondary market"?  Timberland is bought and sold, between private
individuals and by lumber and paper companies, these days perhaps more
by the latter, since as the users of the timber they have a longer
time horizon for investments, especially since in the last twenty odd
years government controls on timber harvesting in some areas have
become onerous, requiring environmental reports that show that no rare
plants or animals or streams will be detrimentally affected by
harvesting.

This is not an "answer" to your question, just a free comment, but if
you have questions, perhaps I can help you further.
Myoarin

this was helpful, just post it as answer and get your $

Thank you,

Peter

tdx,
I am pleased that I could help.  Only GA-Researchers, whose names
appear in blue, can "answer" questions, so my comment is a freebee if
you think it satisfactory.

I forgot to mention that owners of timberland can harvest and sell
their trees themselves, or they can sell "stumpage", letting someone
else remove the trees in a certain area under an agreement that
defines the type of harvest:  selective cutting of trees of a certain
size or clear cutting (which does not have to be the evil practice
that many environmentalist claim it to be).

Good luck, Myoarin