Urban Forest Management Plan
Toolkit

i-Tree

The Streets module in the i-Tree software package provides a monetary estimate of the benefits provided by street trees. Benefits are calculated in 5 areas, energy savings, air quality, CO2 removal, stormwater run-off reductions, and property value increase.

The air quality benefit may turn out to be a negative value because of the way the software calculates the cost of volatic organic compounds that are emitted by many trees. Ozone is formed in still air in the presence of sunlight, nitrous oxides (NOx) and volatile organic compounds (VOC). NOx and VOC can come from natural sources as well as from human activities. About 95% of NOx are produced by burning fossil fuels, such as coal, gas and oil. VOC are carbon-containing gases and vapors such as gasoline fumes and solvents (excluding carbon dioxide, carbon monoxide, methane, and chlorofluorocarbons). The main human sources of VOCs are gasoline combustion and the evaporation of liquid fuels and solvents. Gaseous emissions from plants are a natural or biogenic source of VOC (BVOC). The role of BVOC in ozone pollution continues to be studied, and exactly how much BVOC's contribute to ozone pollution continues to be investigated.

To calculate the benefits of the urban forest, users must input at a minimum species and diameter class of the trees, or a sample of the trees, in the urban forest. Data can be input directly into i-Tree using the inventory software that is a part of i-Tree Streets. Users with a pre-existing inventory must format the species and dbh fields as a Microsoft AccessTM database. Converting an existing inventory into an i-Tree compatible file will be relatively easy for a user with good database manipulation skills (i.e. will take about a day of work based on our experience converting an existing inventory of 37,000 trees).

Calculations in the program are based on one of 16 climate zone-based regional tree guides produced by the Center for Urban Forest Research, UFSF-PSW Research Station. A model city was chosen for each climate zone and figures from this city are used as default values by the software.

CITYgreen

A GIS program called CITYgreen is available from American Forests. CITYgreen is an extension of the popular GIS program ArcGIS available from ESRI, Inc., and can only be used on computers with ArcGIS installed. CITYgreen uses user-supplied imagery to calculate the benefit of the green infrastructure in a city. The user must classify elements in the imagery into landuses such as tree canopy, impervious area, etc. before the analysis can be run by the program.