The city presented the first of three updates on changes to Denton’s tree code ordinance during a Planning and Zoning Commission work session on Wednesday.

The presentation, given by E.J. Cochrum, the city’s urban forester, focused on tree preservation, classification and surveys recommended by Burditt Consultants. The city hired the Conroe-based urban forestry firm last year to revamp the tree code.

The city appears to be moving away from a plan that would require developers to preserve 40 percent of a property’s tree canopy.

Instead, the required percentage of preservation would be determined by the existing tree canopy and the property’s zoning.

Depending on how the property was zoned and its size, the code would require a minimum percentage of the canopy to be preserved; however, about half of that required percentage could be mitigated. That would mean that if developers removed some of the trees, they would have to replant on site or pay into a city tree fund, Cochrum said.

This method “is very nice because we’re actually putting a preservation on each piece of property by zoning district,” Cochrum said.

He also presented a more simplified tree classification system, with three categories — canopy, heritage and historical — down from seven categories.

A canopy tree would be any tree that is 6 inches in diameter and is not classified as a so-called “secondary tree,” or less desirable tree, such as me­squite, bois d’arc, locust, hackberry or cottonwood, he said.

“If we exclude the secondary trees, we can put more into quality trees. I mean, we have to give a little,” said Cochrum. He said that residents want to save protected trees and that developers have questioned why they have to mitigate for secondary trees.

Some commissioners seemed to support the move to exclude secondary trees from protection.

The heritage category would include large trees with trunks measuring at least 75 percent of the diameter of trees of the same species on the Texas Forestry Service’s Big Tree Registry.

A secondary tree could be classified as heritage, Cochrum said, but the city could also decide to exclude them from that category.

Historical trees would have to be identified by the Historical Landmark Commission, city officials said, adding that there are currently no historical trees in Denton.

Cochrum discussed the possibility of an alternative survey method using aerial photos to determine canopy percentage, but city officials would still have to identify the trees on a lot.

City officials say the photo could be no older than three years and would have to come from a qualified source, traditionally the North Central Texas Council of Governments.

Denton has been under pressure for a few years to improve its tree protections.

The current ordinance, passed in October 2004, requires a city permit for most tree removals. It also includes minimum tree preservation percentages that developers must meet, depending on the types of trees, land use and other variables.

However, developers have been allowed to bypass those percentages if they plant new trees or pay a mitigation fee.

The city will address other issues, including tree preservation enforcement, at the next work session, scheduled for Aug. 13.

AMY DODD THOMPSON can be reached at 940-566-6876. Her e-mail address is athompson@dentonrc.com .