Pub 946 also says on page 17:
Land and Improvements Land and land improvements do not qualify as section 179 property. Land improvements include swimming pools, paved parking areas, wharves, docks, bridges, and fences.
New rules under TCJA (see this LINK) did make some changes to allow some assets that were previously not allowed to take a Section 179 to now take the deduction. The following are now permitted:
Qualified section 179 real property.
You can elect to treat certain qualified real property you placed in service during the tax year as section 179 property. If this election is made, the term “section 179 property” will include any qualified real property that is:
• Qualified improvement property as described in section 168(e)(6) of the Internal Revenue Code, and
• Any of the following improvements to nonresidential real property placed in service after the date the nonresidential real property was first placed in service.
1. Roofs. 2. Heating, ventilation, and air-conditioning property. 3. Fire protection and alarm systems. 4. Security systems
