Generally, your basis is going to depend upon whether you have a gain or a loss.
See https://www.irs.gov/faqs/capital-gains-losses-and-sale-of-home/property-basis-sale-of-home-etc/prope...
Presumably, the sale of timber will result in a gain and that gain should be a capital gain (as the sale of a capital asset). As a result, your basis would be a carryover basis (i.e., you take your parent's basis - the donor's basis).
