Reprod Valuations

[Jim]

I'm doing reprod valuations on Douglas-fir plantations.  I use my growth
and yield tables to provide an estimated volume at the end of a determined
rotation, apply today's prices and move the amount back to present value.
Questions,

If I plan on conducting a thinning along the way, what amount of volume
would I base the amount of projected income on.  I have records that would
allow me to calculate a number from within my office but I'm looking for
published material.  Are there tables that supply these volumes?  
Should I even include this thinning? 

What interest rate do I use to move it all back to present net value?  I've
heard I should use average interest rates from the Federal Land Bank (about
10%) and I've heard interest rate from US Treasury Bonds.  I'm assuming
this is quite lower but I haven't found anything that provides a concrete
average for bonds.

Any ideas are appreciated.

Jim