Conducting a street tree inventory is essential to developing a community forest master plan, a critical component in maintaining a healthy community forest and facilitating a future sustainable one. The inventory once completed, however, is but a snapshot of a moment in time. The community forest is continually changing as existing trees are pruned and removed, and new trees are planted. The usefulness of the inventory, therefore, depends to a large degree on keeping current the information it contains. Having made the commitment to conduct an inventory, a community should make the additional commitment to update inventory data as trees are pruned, removed, and planted. A general rule of thumb is that all trees should be resurveyed once every five years.

Updating and maintaining an inventory is easier said than done, especially for smaller communities lacking sufficient resources to employ a dedicated urban forester or purchase sophisticated tree inventory software. Just as the Department of Public Works is often charged with caring for community trees along with all other civic infrastructure, it is also often the responsibility of a DPW to update and maintain the inventory following completion. Given a DPW's many other responsibilities and the demands on its personnel, updating an inventory is frequently placed on the backburner or simply not done. Therefore, whether the responsibility of a DPW, a Shade Tree Committee, or another group within a community, it is important that the process of updating and maintaining an inventory be as straightforward and easy as possible.

Assigning responsibility

It is often not clear within a community, a few years after the inventory, which individual or group possesses the inventory data, much less who is responsible for updating it. A simple, but indispensable first step in updating and maintaining the inventory is clearly assigning responsibility for holding onto the inventory data and making changes to the database. For example, if DPW, a Shade Tree Committee, or another group is expected to undertake these tasks, this needs to be stated explicitly, whether posted on a community website, resolved by village trustees, or confirmed in municipal code.

The inventory process requires someone in the community to be a designated contact person and a public official to sign off in support of the project. It is likely, but not certain, that these individuals, who may in fact be the same, could also be good candidates for keeping and updating the database generated by the inventory. Whoever is charged with these tasks, it is important to spell out clearly the specific responsibilities that are involved, such as data collection and making changes to the database (see below). In addition, stability and continuity should be factors considered in selecting this individual since updating and maintaining the inventory implies a long term commitment to community forest management.

Data Collection

To maintain and update the inventory, additional data needs to be collected as existing trees are pruned and removed and new trees are planted. Data collection post inventory will be most beneficial to community forest management if it parallels the methodology and content of the data originally collected.

If your original inventory data was collected with PDAs using the STRATUM/MCTI PDA Utility, updated data can also be collected this way. This data collection method, however, requires possession of a PDA and proficiency with the STRATUM/MCTI PDA Utility.

A simpler and much less technologically demanding method for collecting updated inventory data is to use a paper survey form. The Paper Survey Template available as a download mirrors the data fields in the current SWAT Team inventories. For additional information concerning these data fields, go to Inventory Methodology.

The primary disadvantage of collecting tree inventory data on paper is that the data, following collection, must be entered manually into the database. Based on the number of trees involved, this can be a daunting task, and collecting tree inventory data on paper is not generally done in large municipalities (although the most recent New York City Tree Census was a paper based survey). Smaller communities, having fewer trees and less data to enter manually, are better candidates for using a paper survey form, especially if data is collected and entered on a regular and timely basis.

Making changes to the database

Once updated inventory data is collected by whatever means, it needs to be entered into the database. Making changes to a database should be approached cautiously. Preservation of the original data must be guaranteed. Subsequent use of the data, whether to analyze changes in species composition in Excel or to run updated STRATUM analyses, can always be replicated so long as the data collected is preserved in its original form. Accordingly, it is recommended that original inventory data either be saved as a separate file or, if utilizing Excel for data analysis, saved as a separate worksheet within the inventory Excel file. For example, in the Sample Tree Inventory Workbook, the All Sites worksheet constitutes original tree inventory data. Before updating any of the data it contains, a copy of this worksheet should be made and saved as a separate worksheet named "Original Inventory Data" or something similar.

Updated inventory data for any trees pruned, removed, and planted after the initial inventory should be given comparable treatment since it constitutes original data as well. As was the case in handling data from the initial tree inventory, the best and safest procedure to preserve original data is to save all updated data as a separate worksheet within the inventory Excel file. This data can then be used to modify the All Sites worksheet in order to keep it current.

The unique Tree ID number assigned to all trees and planting spaces is essential to maintaining and updating the inventory database. This number allows trees and planting spaces to be tracked across multiple worksheets and tables over time. All actions to an existing tree (such as pruning and removal) must be referenced to its Tree ID number, and any new tree planted must be assigned its own unique Tree ID number.

Newly planted trees should not be given the Tree ID number of the planting space it fills. An entry can be made in a data field for that planting space (see the next paragraph) that the space has been filled by a new planting, but that new planting should be given a unique Tree ID number.

Finally, it is recommended that, for each change made to an existing tree or planting space, two new data fields should be added to the database. The first data field entitled "Action1" or something comparable would record the action that was taken, such as "pruned" or "removed" for a tree or "filled by Tree ID # ---" for a planting space. The second data field entitled "Date1" or something comparable would record the date the action was taken. A second change made to that tree or planting space would result in two new data fields entitled "Action2" and "Date2" or something comparable.

Please see the Updating Database Model for a graphic representation of this discussion.

Please see the Utilizing Excel 2003 and Utilizing Excel 2007 tutorials for help in analyzing updated inventory data with Excel.

Please see the Utilizing STRATUM tutorial for help in running STRATUM on updated inventory data.

Back to Conducting a Street Tree Inventory