Taxation of timber land is complex and confusing. The single best piece of advice I can give is to KEEP GOOD RECORDS. Document every expense that you can with the date, purpose, amount (dollars, hours, miles etc.) Keep at least a simple notebook updated at the time the expense occurs. Save receipts. Write everything down and decide later which account to allocate the expenses to. Document mileage to and from the tree farm when maintaining the property. If you travel to a landowner training (like a timber tax workshop) note your miles and other travel expenses.
In general you should EXPENSE costs in the year that they occur. These are short term or annual maintenance expenses like grading a road surface, small hand tools, mileage to perform maintenance etc. Annual property taxes are usually expensed.
DEPRECIATE costs that have a predictable life like a culvert, gate, or fence. Large equipment is usually depreciated.
CAPITALIZE or add to the BASIS cost that improve the land or the trees. The land and trees are separate capital assets. The pioneering of a new road would be a permanent improvement and added to the Basis for the land. Some costs like pruning are allocated to the trees. You recover these costs from a tax standpoint when you sell the asset either the trees in a timber sale or the land.
Wherever you can - Expense, then Depreciate, then Capitalize. The cost of seedlings would be added to the basis but the mileage to pick them up at the nursery and deliver to the planting site would be an Expense. Part of the cost of the truck if used in the "business" of the tree farm could be depreciated.
Where this all pays off is when you eventually sell timber. Many of these costs offset the sale proceeds for tax purposes. With timber you have a lot of costs that add up over time that tend to get forgotten. Then you get a large amount of money in a short time. You want to toss as much of the expense back at the IRS then thereby reducing your income. All this work also pays off in proving "material participation" and the business (vs. hobby) nature of your tree farm.