The SWAT team has conducted forty inventories in New York State communities since 2002 (thirty-two by Central New York SWAT and eight by Hudson Valley SWAT),
and the data collected on tree characteristics, maintenance need, and planting sites have been used to create urban forest master plans for these communities.
Inventory methodology has evolved simultaneously with advancements in technology, availability of software, and experience learned in the field. Data is collected in a walking survey utilizing handheld PDAs (personal digital assistants) equipped with the US Forest Service i-Tree MCTI/STRATUM PDA utility. Data collected includes the following:
(1) Tree Location: Locations for right-of-way trees and right-of-way planting sites are established primarily by property address. If an address is unavailable, a location is assigned based upon the next sequential address. Site numbers are assigned for trees and planting spaces at each address. For addresses with multiple trees and/or planting spaces, site numbers are assigned from left to right facing the property. Trees and planting spaces located at street corners are assigned the property address, but if located on a side street different than the property street address, a notation for "side" is made. Locations for park trees are established primarily by GPS coordinates (see below).
(2) GPS: Latitude (Y) and Longitude (X) for right-of-way trees, right-of-way planting sites, and park trees are collected with handheld GPS (Global Positioning System) units usually accurate between 3 and 7 meters in the Lat/Lon coordinate system with a WGS 84 Datum. Coordinates for right-of-way trees and planting sites are corrected after the inventory to approximate more accurately addresses based on a parcel shapefile typically supplied by the county GIS Department. Coordinates for park trees are not generally corrected.
(3) Location Site: Placement of trees and planting sites is assessed by one of five ratings: 1= front yard or lawn; 2 = treelawn planting strip less than four feet wide; 3 = treelawn planting strip greater than four feet wide; 4 = sidewalk tree pit; 5 = street median.
(4) Species: Trees are identified and assigned their respective botanical names. Common names are added subsequent to the inventory.
(5) DBH: Trunk diameter at breast height (approximately 4.5 feet above the ground) is rounded to the nearest inch. DBH is the most commonly used measure of tree size and age. It is not an absolute measure, however, as relationships between DBH and canopy spread or DBH and tree age vary by species.
(6) Condition Wood: The health of a tree's wood (its structural health) is assessed by one of four ratings: 1= Dead or Dying - extreme problems; 2 = Poor - major problems; 3 = Fair - minor problems; 4 = Good - no apparent problems.
(7) Condition Leaves: The health of a tree's leaves (its functional health) is assessed by one of four ratings: 1= Dead or Dying - extreme problems; 2 = Poor - major problems; 3 = Fair - minor problems; 4 = Good - no apparent problems.
(8) Percent Deadwood: "Deadwood" refers to branches that are dead, dying, or diseased. The percentage of deadwood in the tree canopy is assessed by one of five ratings: 1= less than 10%; 2 = 10 to 25%; 3 = 25 to 50%; 4 = 50 to 75%; 5 = greater than 75%.
(9) Maintenance Recommendation: Tree maintenance needs are assessed by one of four ratings: 1= None - no maintenance necessary; 2 = Train - routine maintenance for a young tree; 3 = Routine Prune - routine maintenance of a mature tree; 4 = High Priority Prune - a tree requiring immediate maintenance.
(10) Consult Needed: Based on the condition of the tree, an assessment is made as to whether a certified arborist should be brought in to examine the tree.
(11) Sidewalk Damage: The presence or absence of damage associated with tree roots where the sidewalk was heaved at least ¾ inch is noted.
(12) Wire Conflict: The presence or absence of single or triple phase overhead utility wires is noted.
Note: some data fields above approximate, but are not identical to data fields used by STRATUM to quantify street tree benefits. These fields will need to be re-coded in order to run accurately in STRATUM. Moreover, some data fields are not equivalent at all to STRATUM data fields, but have been included because they provide information important to community forest management and health.
Each fall, prior to the first scheduled inventory, anyone participating in an inventory attends a mandatory half-day training session to review inventory procedures. This includes those who have participated in inventories before as well as those who have not since changes may have been made from the previous year in data fields, equipment, etc. and a refresher on correct inventory procedures promotes better data collection accuracy.
The training session includes classroom instruction in which students familiarize themselves with the PDAs and GPS units used in the inventories and watch a PowerPoint presentation explaining inventory procedures. A particular focus of the PowerPoint presentation is to explain the important reasons for doing the inventory in the belief that an understanding of these reasons will increase the motivation of those conducting the inventory and produce fewer errors in data collection.
The classroom instruction portion of the training session is followed by a brief field exercise on nearby streets in which data on street trees is collected. This exercise provides valuable hands-on experience in actually conducting an inventory. In addition, since the streets in the exercise have been inventoried previously, data collected in the exercise can be quickly checked for accuracy to identify any problems with the equipment or individuals having trouble with inventory procedures. These are important considerations since it is far easier to deal with any problems at this stage in the process than after inventories have been conducted.
Participants conducting an inventory are typically sent out in pairs. Each pair makes up a team and each team is equipped with the following:
- A street map of the section of the community which the team has been assigned
- PDA (handheld computer)
- Trunk diameter tape (converts trunk circumference to diameter)
- Notepad and pen for writing down comments or residents questions
- Orange safety vest for each team member
- Tree identification guide (if desired)
Each team must have at least one person proficient at tree identification. This person is typically the "caller" and it is the responsibility of the caller to note street addresses, take GPS readings, identify tree species, assess tree size and condition, note the presence or absence of utility wires, etc., or, in other words, to gather inventory information. The second person in the team, who is sometimes called the "tapper," enters this information into the PDA.
Making maps for inventory participants is an important step in the inventory process which needs to be addressed prior to the inventory itself. The better the maps, the quicker and more accurate the inventory is likely to be.
Maps are of two types: a master map showing the entire community and all streets to be inventoried, and maps for each team showing the section of the community each team has been assigned to survey. Each section should be sized so that a team has a realistic chance of completing the survey of that section by the end of the day.
It has been our experience in SWAT that assigning addresses to locations can be challenging and time-consuming, whether because the parcel is a vacant lot, an address is not marked, or the address belongs to a building located on the street corner. Accordingly, we now provide our teams with maps which show not only streets and street names, but also parcel boundaries and the addresses associated with those parcels. These maps can be "tax maps" previously prepared for real estate assessment, or they can be prepared from scratch using GIS software.
It is also extremely important that right-of-way information for each street be appended to these maps. This information can be contained in a table found on the back of each map so that it is conveniently available to the inventory teams as they proceed from street to street.
Finally, the progress made by each team during the inventory should be delineated on the master map by marking all street segments which have been inventoried. This should be done both during lunch and at the end of the day to make sure that all streets have been surveyed and no streets have been surveyed twice.
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© Copyright, Department of Horticulture, Cornell University.