Assessing Street Tree Populations
Within i-Tree, street tree populations are assessed using STRATUM (Street Tree Management Tool for Urban forest Managers). Developed by researchers at the Center for Urban Forest Research -- a research unit of the USDA Forest Service's Pacific Southwest Research Station -- STRATUM is a computer application that uses tree inventory data to quantify the structure, function, value and management needs of any street tree resource.
What is STRATUM?
STRATUM is a street tree management and analysis tool for urban forest managers that uses tree inventory data to quantify the dollar value of annual environmental and aesthetic benefits: energy conservation, air quality improvement, CO2 reduction, stormwater control, and property value increase. It's an easy-to-use, computer-based program that allows any community to conduct and analyze a street tree inventory. Baseline data can be used to effectively manage the resource, develop policy and set priorities. Using a sample or an existing inventory of street trees, this software allows managers to evaluate current benefits, costs, and management needs. Use STRATUM to:
- Improve the return on your investment dollar by determining which trees maximize canopy cover and provide the benefits that are important to your community.
- Determine the management needs of your street tree resource to foster and perpetuate a healthy municipal forest.
- Leverage investment from partners for such things as carbon credits or energy conservation.
- Gain public support by demonstrating the value of trees to the quality of life in your community.
- Perform economic evaluations of tree performance using annual budget and expenditure data.
- Assess costs of management -- rather than benefits alone -- to provide a platform for strategic planning.
What does STRATUM do?
STRATUM uses tree growth and benefit models for predominant urban tree species in 16 national climate zones. Users import data collected in a sample or complete inventory and enter community specific information (e.g., program management costs, city population, and price of residential electricity) to customize the benefit-cost data.
STRATUM uses this information to calculate:
- Structure (species composition, extent and diversity)
- Function (the environmental & aesthetic benefits trees afford the community)
- Value (the annual monetary value of the benefits provided and costs accrued)
- Management needs (evaluations of diversity, canopy cover, planting, pruning, and removal needs).
Reports consist of graphs, charts, and tables that managers can use to justify funding, create program enthusiasm and investment, and promote sound decision-making. With STRATUM, users can answer the most important question related to their tree program: Do the accrued benefits of street trees outweigh their management costs? In addition, STRATUM will aid managers in improving the return on their investment dollar.
The first steps in the start up of a STRATUM project are:
- Define the street tree population for the project you wish to conduct. The population can range from a single planting site on a block of interest to a particular neighborhood, but it is more commonly the entire city street tree population. Users have the option of analyzing an existing street tree inventory or completing a new STRATUM-compatible inventory.
- If an existing street tree inventory is not available, users must decide whether a complete or sample inventory of their community's street trees will be conducted. For very small populations (<3,000 trees), complete data collection is a good option. For larger populations, the i-Tree Sample Inventory Generator can be used to generate a statistically valid, STRATUM-compatible random sample of street segments. Depending on the size of the city, experience has shown that sampling 3-5% of all street segments will return a sampling error of 10% or less.
Select from the options below:
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