THE TREE INVENTORY
What is a tree inventory?
A tree inventory is the gathering of accurate information on the health and diversity of the community forest. How
many street trees are there? What kind? In what condition are they? You cannot manage the community forest effec-
tively unless you know its condition. Tree inventories are an essential tool of good management.
Why should my community do a tree inventory?
There are many good reasons for doing a tree inventory in your community. The inventory may be used:
- To determine the need for a community forestry program. For example, if the inventory reveals many dead and diseased trees or areas that are bare of trees, this suggests that a program incorporating tree planting is badly needed.
- To prioritize maintenance schedules in order to reduce the potential liability that results from hazardous trees. It also streamlines the efficiency of street crews and facilitates long-term budgeting.
- To educate residents about the benefits of a healthy, well-managed community forest, and to inform them about species best suited to the community.
- To facilitate the planning that is essential to the community's quality of life.
- To provide the basis for the development of a comprehensive community forestry management plan.
What information should be collected during an inventory?
Only data that will be put to use should be collected. Your community must determine what objectives it wishes to achieve prior to conducting an inventory. Bear in mind that information translates into expense: the more data gathered on each tree, the greater the cost of the inventory. Generally however, information on the following is collected:
- Species: To avoid costly mistakes, record the scientific names of trees. Don't use common names or codes.
- Size: DBH (diameter at breast height- 4.5 feet above ground), height and crown spread.
- Condition: Indicate what maintenance procedure is needed. Does the tree need corrective pruning? Does it require removal? It is important to note that if the tree is deemed to be a hazard to the public and removal is mandatory, rather than record "hazardous", it is prudent to record "removal."
- Damage: Record insect infestations, injuries and diseases by indicating the precise procedure necessary. For example, rather than describe lightning damage, indicate the need for pruning or removal. It is prudent to have a skilled tree crew correct the problem as soon as possible.
- Management/maintenance: Record need to fertilize, apply fungicide/insecticide, prune, repair curb and/or sidewalk damage inflicted by roots, remove stump/tree, or plant in an empty planting site. Do so in order to schedule maintenance work, allocate equipment and prepare budgets.
- Site characteristics: How much space is available for the root system? What is the condition and health of the soil in the planting space? The proximity of overhead/underground utilities and tall buildings? The potential for road salt/traffic damage? Is it zoned commercial?
- Planting spaces: Research suggests that a community should give highest priority to planting trees on streets where yard trees are few. Identify planting spaces to encourage the planting of bare areas.
- Historic/Distinctive Trees and Groves: Special trees require more intensive management. (Note that trees of this nature may also serve to justify the inventory itself if the community is hesitant to undertake a management program.)
What type of inventory should my community do?
There are many different types of inventories and you should select an inventory type only when you know precisely what you want to accomplish. Data gathered on your communitiy's trees must have practical value. To guarantee that your tree management program will be effective today
and useful tomorrow, you must match an appropriate inventory to your objectives. The most common types include:
- Specific Problem inventory: Gathers data about a specific problem or condition for work contracts or work schedules. For example, a survey of hazard trees or the extent of Dutch elm disease are specific problem inventories. Note that every community should conduct a yearly survey of hazardous trees. (Marking hazardous trees is not recommended since doing so may increase liability.)
- Partial Inventory: Gathers data from a sample (or samples) and information is extrapolated to apply to the whole forest. Survey is easily completed by an observer walking or driving and is generally used to work out maintenance contracts.
- Complete Inventory: Surveys the entire tree population but it is time consuming and expensive.
- Cover-type Survey: Information is gathered by at least partial use of aerial photographs and sometimes with geographical information system. This type of survey is used increasingly in urban areas to examine the entire tree population in order to plan long-term land use. It is especially useful in intensively managed areas such as parks and campuses, but it can be expensive and produces detail that few community tree management programs can use effectively.
How should the inventory be done?
The tree inventory may be done by professionals or volunteers, but, in either case, all crews, regardless of experience, require training before and during the inventory. (Please note that it is advisable that the municipal tree warden assist or lead the tree inventory process. It is also advisable that a person trained in hazard tree assessment review all trees surveyed and assess them for hazardous condition.)
Individuals working alone tend to be more productive, but crews attract attention, and this fact may be exploited to good advantage: professionals who carry brochures about the tree management program and the inventory can educate community residents. Crews should wear uniforms if possible and carry identification cards. Where crime is a problem, two or more people must work together for safety.
When should the inventory be done?
During the summer favorable weather makes inventory work more pleasant and students are often available to help, On the other hand, winter conditions allow crews to observe trees for hazardous limbs and dead wood. Professional foresters often choose to conduct inventories in the winter.
How should the inventory be updated?
Tree populations undergo constant change, and, as an inventory ages, it becomes less accurate and useful. No inventory will provide information that is useful beyond five or ten years. Consider the damage a single storm can
do. Hurricane winds can render an inventory obsolete overnight. The ideal way to keep the inventory current is to make use of specially designed computer programs that provide easy and logical locations for data entry specific to tree inventories. Good programs also allow you to easily
query data and produce reports, graphs, tables and perform some statistical analysis.
Stress conditions exist in the community firest severely affecting health of individual trees. Those trees that pose a hazard to public safety need to be detected and treated by removal or pruning as soon as possible. It is
prudent that the municipal tree warden assess trees for hazardous conditions frequently.
Robert M. Ricard
Extension Educator, Urban and Community Forestry
West Hartford Extension Center
1800 Asylum Avenue
West Hartford, CT 06117