Arboriculture & Urban Forestry 44(2): March 2018 lacked precision, creating operational difficul- ties at locations like large buildings fronting mul- tiple streets with multiple trees, or trees in center medians. Imprecise locations resulted in confu- sion when tree workers were deployed to spe- cific trees sharing a single address with others. Further, in 2005, the address-based method resulted in over 23,000 trees that could not be geocoded because of incorrect location data. To increase the accuracy of spatial locations, NYC Parks considered methods developed by TreeKIT (Silva et al. 2013) and OpenTreeMap (OpenTreeMap 2017). TreeKIT uses linear refer- encing, where participants use a surveyor’s wheel to measure along lengths of sidewalk (blockedges) from a start point and enter distance-to-tree mea- surements into paper datasheets. The data from one blockedge comprises one survey. These linear measurements are then geocoded using linear ref- erencing methods in GIS. OpenTreeMap utilizes GPS and manual placement of tree-points on aer- ial imagery on a tablet. NYC Parks evaluated both methods in a small pilot with citizen scientists who all preferred the TreeKIT method, citing ease of use and understanding. NYC Parks implemented a simplified version of the TreeKIT method (omitting tree pit measurements) for TC2015. NYC Parks contracted with a software com- pany, Azavea (Philadelphia, Pennsylvania, U.S.), to create a web-based data-collection applica- tion that citizen scientists could access on any web-enabled device, as recommended by Silva et al. (2013). The code for this web application is currently available on GitHub (Azavea 2017), a software development platform, and a full open-source data-collection toolkit is in devel- opment. The application supported in-field data entry and visualization of collected tree loca- tions overlaid on aerial imagery for review before submission. The application also featured a live interactive map that displayed the collection sta- tus of all city blockedges, allowing participants to independently identify locations requiring data collection, and reserve them for collection. This shift to digital data collection eliminated the need for manual data entry, an intensive part of both previous inventories fraught with transcription errors. The web application also prevented the submission of incomplete data by 51 precluding blank fields, enabled live progress reporting, and a near-real-time quality assur- ance (QA) process (Houston and Heider 2009). Inventory Variables Table 1 outlines the variables included in 1995, 2005, and 2015 by category, and describes changes between inventory years. The general categories of variables are metadata, location, tree, infrastruc- ture, and site. In-depth descriptions of each of the 2015 variables can be found in the training manual, included in the online supplementary material. NYC Parks weighed the need for accurate and robust data for management with the need for a streamlined collection protocol suitable for lay- persons (Ferretti 2009; Kosmala 2016). Variables from 1995 and 2005 were re-evaluated, and Öst- berg et al.’s (2012; 2013) research was consulted to ensure TC2015’s variables were comparable to pre- existing data sets to allow for cross-study compari- sons. Four of the top-five variables recommended by Östberg et al. were included: tree species, vital- ity class (Tree Condition), coordinates, and tree ID number. Species, condition, and coordinates (from the TreeKIT method) were included in field data collection, and tree ID number was auto-generated by the web application. Östberg et al. (2012; 2013) also included “risk posed” in their top-five recom- mended variables, although NYC Parks chose not to include this variable because citizen scientists are not qualified to perform tree risk assessments. The Stewardship variable was a new addition in 2015, based on Lu et al.’s (2010) research sug- gesting the quantity of stewardship signs present at a tree correlates positively with survivorship of young street trees. Quantity of stewardship signs refers to the number of individual signs of steward- ship noted for a single tree and includes indicators such as the presence of plantings, “curb your dog” signs, and mulch. This study also found a positive correlation between the presence of a tree guard and survivorship; as such, the Tree Guard variable from 2005 (previously called Vertical Treatment) was retained in an altered form. Other variables altered but retained were Tree Problems, Tree Con- dition, and Tree Circumference. The Tree Problems variable was renamed from the 2005 variable Infra- structure Conflicts because it was perceived as easier to understand. Tree Condition, as collected ©2018 International Society of Arboriculture
March 2018
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