A tree inventory is a survey of individual trees within a given area. It is a necessary process and product to understand the make-up of an urban forest and make informed decisions about tree care. Thus, it is critical to the long-term success of urban forest management.
Tree inventories are used for many purposes, particularly to schedule tree maintenance, identify tree health issues or risks from pests and pathogens, develop urban forest policies, communicate tree benefits and identify tree planting locations. However, there is no shortage of uses for a tree inventory; your imagination is the limit.
Types of data collected
The type of tree data collected by an organization should be dictated by the needs of the organization. There is no need to collect data that is useless for the organization’s purposes. However, there are some tree attributes that are commonly collected. These attributes include:
- location (e.g. latitude and longitude and street address);
- diameter at breast height;
- health; and
- inventory date.
There are countless other attributes that many organizations collect, but each organization should choose which best serve their goals. Note however, that those communities and organizations conducting tree inventories using DNR Urban Forestry Grants are required to collect certain attributes .
How to conduct an inventory
There are many options for conducting a tree inventory. First, the organization must determine the type of tree inventory they want. A complete inventory captures every relevant tree in one’s area of concern (e.g., a city’s street trees). A sample inventory only collects a segment of the complete inventory but then extrapolates the data to the wider area. As could be surmised, the complete inventory is more comprehensive but it is more expensive and time consuming. Additionally, one might choose to conduct a problem inventory for which one’s only concern is documenting a certain subset of trees (e.g., ash trees susceptible to emerald ash borer).
One must also consider who will conduct the inventory. Some communities contract with an outside arborist to pursue the inventory, while others do it using in-house staff. Others still use volunteers, interns or students. Each group offers its own advantages and disadvantages, though it is always important to have arborist expertise involved in the process. Especially for communities managing a large urban forest, proper identification of trees and their health concerns is of the utmost importance and might necessitate contracting with your friendly neighborhood certified arborist.
For help identifying common urban trees, see the Wisconsin Urban Tree Key.
Hardware and software
While the data for tree inventories has traditionally been collected with paper and pencil, there are now a wide array of digital technologies available. The use of digital devices can greatly increase efficiency. Strive to use the method that matches the ability of participants, but digital methods are highly encouraged for short-term efficiency and long-term viability.
There are multiple software options* to be used on smart devices (e.g., phones and tablets). Some of these are free and available to the public while others are commercial products* requiring the purchase of software or a subscription. Generally, free options have fewer tools and are less user-friendly but may be perfectly fine for projects, especially smaller ones. However, programs developed for the complicated management of tree maintenance scheduling, complaint documentation and report generation are most likely to be commercial products (unless developed in-house).
*Note that we do not endorse any of these individual products, but are offering suggestions based on others' usage.