The Tree Technical Manual

Prof. Buck Abbey, ASLA, Landscape Architect, Robert Reich School of Landscape Architecture, Louisiana State University

Improper tree pruning practices are common, often a result of tree trimmers ''resizing'' trees. That?EUR??,,????'???s why communities like West Linn, Oregon have a Technical Tree Manual. That manual states the ''most compelling reason to prune trees is to develop a strong, safe framework.''' It further notes: ''All specifications for working on trees shall be written and shall be administered by a qualified arborist, and shall be designed to promote the preservation of tree structure and health.''

''The city is seeking to improve these rules to address changing development patterns, address water conservation and make the ordinances easier to follow.''
?EUR??,,????'??+Round Rock, Texas Development Services 2011

The city of Round Rock, Texas has a Tree Technical Manual as the basis of its Tree Protection and Preservation Ordinance. The tree ordinance (Chapter 14-Environment, Article II-Tree Protection and Preservation, ?????? 1/4 14-19) is directly tied to the Tree Technical Manual in ?????? 1/4 43-20 of the proposed draft ordinance now under discussion. After many successful years of use, the city is now upgrading its tree ordinance. The draft ordinance (dated 11.16.11) consists of 16 sections that provide subsections to the regulation that cover several central areas backed by technical content of the Tree Manual. Included in the ordinance are tree protection strategies that depend upon tree species, sizes, types and characteristics of protected trees, especially those defined as ''Monarch'' trees, those that are 80 percent of the diameter (or larger) for the species, Subsections also provide rules for permitting, removal, replacement and mitigation for removed trees.

This ordinance provides guidelines for tree inventory, tree protection and administration. Administrative procedures mentioned in the code include the use of the Tree Technical Manual, fiscal security, inspections and enforcement. Finally the ordinance sets forth regulations to identify violations, penalty and appeals.

This ordinance is a good example of how a community balances the preservation of tree canopy with the need for urban development.

But what is most special about this code is the Tree Technical Manual is used to set forth explicit arboricultural specifications. These specifications are central to the understanding of protected and unprotected trees, and requirements for methods of gathering tree data in the field and reporting it on the tree survey.

Tree surveys must specifically determine which trees are larger than 8-inch diameter at breast height (DBH), and which trees are considered Monarch trees. Smaller native trees can be identified in the field if tree credits are sought against proposed landscape plan requirements. Tree characteristics that are to be identified include location, diameter, species general quality and limits of construction near critical root zones (CRZ). Tree surveys must be certified. Licensed arborists, registered landscape architects or professional land surveyors may certify the tree survey.

Tree protection standards to be followed during construction are very specific. They include preparation of a tree protection plan, primarily for the protection of critical root zones. The plan must consist of three elements that include tree fencing details, specifications as listed in sec. 2.3.2 and tree protection symbols as seen in illustration 2.2 in the manual.

The tree removal replacement, planting and maintenance standards of this manual are detailed with notes, specifications and drawings. Typical subsections include a tree replacement plan, planting requirements for tree species, spacing, tree standards, planting materials and planting site preparation. Further specifications are given for planting, transplanting, staking, pruning, drainage and aeration.

Pruning trees early improves their life expectancy, is a proven, cost-effective measure and makes for safer trees with fewer branch failures, says the West Linn, Oregon Technical Tree Manual. This Liquidamber styraciflua snapped during a thunderstorm, a reminder of the importance of pruning young trees to prevent or remove narrow branch crotches.
Photo courtesy ofPurdue University

It's curious that there are no standards for the use of mechanical tree spades, fertilization and insect and disease control.

There are excellent illustrations in this manual that can be used by landscape architects when they want to draw proper details for tree protection or planting.

Proposed Changes in Round Rock
Proposed changes to the tree ordinance are primarily concerned with revisions to tree mitigation standards. Mitigation is accomplished by planting a replacement tree, or paying a per inch fee to the Tree Fund, or some combination thereof.

New tiers for tree mitigation are established using several replanting ratios. The ratios vary: 1:1, 2:1 and even 3:1, based upon the size and classification of the tree removed. A 1-inch replacement for every one-inch removed is currently used for all trees. Under the new schedule a 2:1 ratio is used for all trees larger than 20-inch DBH, but smaller than a Monarch tree. Monarch trees command a 3:1 ratio. The tree replacement by inch schedule is $150 up to a 20-inch tree; beyond this it is $450 an inch. Monarch trees can only be removed by city council action. Old large native trees are protected in this community.

Other changes include: a parking requirement incentive for saving trees larger than 15-inch DBH; a Champion Tree Register of monarch species by DBH; reducing the size for monarch status for Quercus virginiana from 46 inches to 36 inches; providing fiscal security, or 50 percent mitigation fees, for trees with 25-40 percent critical root zone encroachment.

First Principles
The first principles of urban tree care should be set forth in a tree technical manual. These principles must include building a strong purpose behind the need for community trees and there management. Ordinances and tree technical manuals must establish standards for tree care, preservation, protection, specifications and instruction on urban forestry sustainability. Tree manuals are an indispensable addition to any community tree preservation and protection ordinance. Each community should have its own manual to assist in tree management.