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.
Hazardous trees
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
(860)570-9257
