16 U.S.C. § 504
Purchases of tree seeds, cones, forage plant seed, and nursery stock for national forests
The provisions of section 6101 of title 41 shall not apply to any purchase by the Forest Service of forest-tree seed or cones or of forage plant seed when the amount involved does not exceed $10,000, nor to any purchase of forest-tree nursery stock when the amount involved does not exceed $500, whenever, in the discretion of the Secretary of Agriculture, such method is in the public interest.