Where do I enter income from a timber sale?
If you received money from the sale of timber, you'll probably get a Form 1099-S. Some people will get a 1099-MISC, which is (technically) the wrong reporting form per the IRS.
Regardless of which form you received, timber income is reported in the investment section. Just follow these instructions; don't enter the sale in the 1099-S or 1099-MISC section or you'll go down the wrong path.
For your cost basis, most people will enter a 0, but you could enter what you originally paid for the seedlings or saplings. On the More Info About This Sale screen, you'll want to select Everything Else, located at the bottom of the screen.
Tip: TurboTax doesn't support IRS Form T (Timber) but the good news is that you probably don't need this form. It's only needed "...when a sale or deemed sale under sections 631(a), 631(b), or other exchange has occurred during the tax year" to quote the IRS. See the IRS instructions for Form T.