Overview
The Roanoke City Urban Forest Assessment is being conducted using the i-Tree Eco protocol developed by the USDA Forest Service. The assessment entails a field inventory of sample plots located throughout the City. Data collected from these plots are then analyzed using i-Tree Eco software, which provides estimates of tree abundance, composition, and condition for the entire City. In addition, the software provides estimates of urban forest benefits (such as air pollution abatement, stormwater mitigation, and energy conservation) using mathematical computations from the Urban Forest Effects (UFORE) model developed by researchers at the USDA Forest Service. The assessment comprises three phases: (1) pre-field work to establish sample plots and obtain property access rights; (2) field work to collect data from sample plots; and (3) post-field work to compile and analyze plot data.
Pre-field Work
The Roanoke City Urban Forest Assessment uses data from 155 field plots located throughout the City. To establish these plots, over 40,000 parcels and adjacent right-of-ways in the City were first classified as industrial, commercial, residential, or under-developed based on City zoning standards and an assessment of tree canopy cover performed in 2009. Once classified, a GIS program was used to randomly place field plots in each land-use stratum. Because the majority of field plots reside on private property, the initial plot assignment was over-sampled by 2.75 times (426 plots total) to account for denial of parcel access by owners and ensure that the 155 plot goal can still be achieved. Using City tax parcel data, the owners of parcels containing potential field plots were identified. Parcel owners were then contacted by letter or phone to request permission for property access to collect field data.
Field Work
Once the locations of the 155 field plots are finalized, research technicians will begin collecting field data. This entails visiting each plot to measure trees and characterize the landscape. Each tree residing within the 1/10th acre plots will be identified by species, measured for physical dimensions (trunk girth, crown width, total height), and evaluate for health. In addition, land use, ground cover type, and available tree planting space within each plot will be categorized. Additional information on field data collection can be found here. Depending on how many trees are located within a plot, field data collection for each plot should require 20 to 40 minutes. Data collection is non-destructive and no markings are left on trees or the landscape.
Post-field Work
Once field plot measurements are complete, data will be compiled and analyzed using the i-Tree Eco software. Data will first be checked for errors and inconsistencies, corrected, and then sent to USDA Forest Service for formatting. In addition to the field data, weather and air pollution data specific to Roanoke City will be input to i-Tree Eco to permit analysis of volatile organic compound emissions and air pollution removal by the urban forest. Results of the i-Tree Eco analysis will be summarized in a report presented to the project partners (VA Dept. of Forestry and Roanoke City) and posted to the project website for public access.