How are net receipts from an interest in timber treated?

Net receipts are allocated 10% to income and 90% to principal

Net receipts are allocasted entirely to income if received under a contract to cut timber from land owned by the trust

Net receipts are allocated to income to the extent the amount of timber cut does not exceed the rate of growth during a period there is a beneficiary with a mandatory income interest

Net receipts must be accounted for by the trustee under the separate business accounting rule