What is a tree inventory?
A tree inventory is the assembly of accurate information on the health, diversity, location, and maintenance needs of the urban forest. How many street trees are there? What kind? In what condition are they? How many potential planting sites are there? What sort of work is recommended for each tree? How can we use our tree budget wisely by prioritizing tree maintenance? You cannot manage the urban forest effectively unless you have one essential management tool - an updated and accurate tree inventory.
Why should my organization do a tree inventory?
There are many good reasons for doing a tree inventory. The inventory may be used:- To determine the need for an urban forestry program. For example, if the inventory reveals many dead and diseased trees or areas that are bare of trees, this indicates the need for a program incorporating tree planting.
- 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 urban forest, and to inform them about species best suited to various locations.
- To facilitate the planning that is essential to the community's quality of life.
- To provide the basis for the development of a comprehensive urban forestry management plan.
What information should be collected during an inventory?
Only data that will be put to use should be collected. Your organization must determine what objectives it wishes to achieve prior to conducting an inventory. Most often we collect the following information:- Species: - Common & Botanical
- 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 an organization should give highest priority to planting trees on streets where yard trees are few. Identify planting spaces to encourage the planting of bare areas.
What type of inventory should I 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 urban forest 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. This is the only way to maintain an accurate list of hazard trees, full species diversity, vacant planting sites, and a prioritized list of maintenance needs.
- Cover-type Survey: Information is gathered by at least partial use of aerial photographs and sometimes with GIS. 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. Keep in mind that tree inventories done by volunteers frequently take much longer than expected. Knowledgeable volunteers may have limited time, experienced arborists may have limited experience with GPS technology, and GIS professionals with extensive GPS background may have trouble identifying tree species, and issues such as pests, decay, and evidence of improper pruning techniques.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 more daylight hours are available. On the other hand, winter conditions allow crews to observe trees for hazardous limbs and dead wood. Professional arborists can adapt to nearly any month of the year.
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 to seven 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 software that provides 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. ArborPro provides all this and more.