 Assessing Street Tree Populations
Data Needs for Sample Inventory Project
STRATUM is not an application intended for the day-to-day tracking and management of the street tree resource. There is no facility within the application for recording individual tree locations (e.g., trees' addresses or GPS coordinates). STRATUM was developed for use as a simple resource assessment tool for short- and long-term planning based on economic valuations of tree performance and summaries of management needs. However, reports can help users develop policy, set priorities, and make sound management decisions that ultimately affect day-to-day management of street trees.
The data needs of STRATUM depend on the nature of the output desired. STRATUM's adaptive nature allows for communities to tailor their sample inventory to meet their planning and assessment needs. Any combination of tree attributes can be inventoried as long as the species, diameter at breast height (DBH), and street segment ID are included for every tree in the inventory. However, to utilize the full range of STRATUM's analysis and reporting features, users can follow protocols for STRATUM's default data fields as a guideline for field data collection. Additional information will be needed to describe and define the community, species information, and sample inventory parameters.
Field data inputs:
The functional capacity-benefits related to street trees-can be assessed with minimal field data input (i.e., species and diameter at breast height). However, the ability of STRATUM to report on the structure and management needs of the resource is determined, in part, by the extent of field data collected. Depending on the report types desired, needed attributes will include location, condition, and maintenance needs.
Inventory data
Users can utilize any combination of commercial or in-house software and data collection regimes to collect field inventory data. Whether paper-based or electronic, most inventories can be formatted for STRATUM analysis after the inventory is completed. However, efficient and compatible complete inventory field data collection is facilitated by the i-Tree companion PDA Utility. Users can configure STRATUM to analyze up to 17 data fields. These data can be a combination of actual measured values or values classified as a range. Data fields are defined within the application or i-Tree PDA Utility and are customizable to meet the protocols and definitions of most any community's inventory needs.
Sampling Street Segments
STRATUM uses a complex set of estimators and standard error equations and, therefore, only accepts sample inventories that follow the simple random sample conventions. The Sample Inventory Generator Utility is based on access and utilization of the TIGER database developed by the U.S. Census Bureau. The term TIGER comes from the acronym Topologically Integrated Geographic Encoding and Referencing which is the name for the system and digital database developed at the U.S. Census Bureau to support its mapping needs for the decennial Census and other Bureau programs.
The TIGER data base defines the location and relationship of streets, rivers, railroads, and other features to each other and to the numerous geographic entities for which the Census Bureau tabulates data from its censuses and sample surveys. It is designed to assure no duplication of these features or areas. The TIGER database integrates a variety of encoding techniques such as automated map scanning, manual map "digitizing," standard data keying, and sophisticated computer file matching.
By utilizing the TIGER database, the Street Segment Generator provides a randomly drawn sample of street segments for inventory. Segments are mapped and a database is created with segment IDs and addressing information.
Sampling intensity is determined by the user. Generally, a 3-6% sample of street segments, depending on community size, will produce about a 10% standard error for the total number of trees. Smaller communities and towns have used sampling intensities at the 6% level, while large communities such as Minneapolis, MN have used 3% samples.
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Species data
The i-Tree PDA Utility has integrated species lists for each region's most predominant species to facilitate tree identification and STRATUM-compatible formatting, which requires species data to be imported in species code format (generally, the first two letters of the genus and species epithet combined to form a four letter code). For other data collection methods, STRATUM recognizes a comprehensive species list for each of the 16 national climate zones. However, most communities will find that after importing an inventory into STRATUM, several species will not be recognized. You will be prompted to define each unrecognized species with a species code, scientific and common names, and an allied match of species form and mature size (e.g., broadleaf deciduous large).
Management inputs
Though optional, city and costs data inputs allow users to utilize the full functionality of STRATUM's reporting features. For example, without entering street-tree program expenditures, users will not get a Benefit-Cost Ratio (BCR) report, though benefit information will still be reported. The more information (inputs) you enter, the more information STRATUM will return in the form of reports.
City data
These data are information about a user's community that can be used by STRATUM to report per capita values for benefits and costs and canopy cover reports. Typically, these inputs are easily accessible data and include parameters such as total land area, resident population, and total linear miles of street are entered.
Cost data
To provide meaningful benefit-cost ratio reporting, users are encouraged to provide up-to-date, complete and accurate cost information. Cost data include all internal and external programmatic annual costs associated with managing the street tree resource (e.g., pruning and storm clean-up costs). While STRATUM will run without costs inputs, the benefit-cost ratio reported will reflect only costs entered by users.
Benefit data
Benefit inputs allows the user to define the dollar value of tree-related environmental services associated with street trees. For example, the cost of a single kWh of residential electricity charged to consumers in order to establish the dollar value associated with reduced summer energy use from tree shade. Default benefit values are included for each of the 16 national climate zones and are based on prices typical for the region. Users have the option of changing these values where more city-specific data are available.
Select from the options below:
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