Arboriculture & Urban Forestry 46(2): March 2020 2002). The diverse climate led us to believe there would be a diverse selection of tree species. Additionally, this is an area where ISA certification is the primary professional certification for arborists. Study Design The sample frame was developed in conjunction with staff from the Oregon Department of Forestry and the Washington Department of Natural Resources. Pri- mary contacts for each Tree City were provided, which consisted of urban foresters, park staff, and others (collectively referred to as “managers”). The initial 22-question survey instrument was developed using Qualtrics (Qualtrics 2017) and was approved by a University Institutional Review Board (IRB). Primarily closed-ended quantitative questions were used to examine tree species selection criteria. The survey was targeted toward managers who plant pri- marily on public lands. An initial pilot survey was sent to Tree Cities in Idaho to validate the survey questions. The pilot sur- vey included an extra question to test for clarity and ease (Vaske 2008). Responses from Idaho deemed the survey comprehensive and no further iterations were needed; therefore, the same survey instrument was sent to the primary contact for Tree Cities in the PNW. Out of 151 potential municipalities, 79 responded (52.3% response rate), with 6 municipalities provid- ing responses from different departments, for a total of 85 responses. Sample size varied between ques- tions, ranging from 60 to 85. Participants were asked to base their responses on tree species choices on public land and not on private property. Using meth- ods outlined by Millar and Dillman (2011), an attempt was made to increase response rate. An initial contact was made via email, requesting participation in the survey. The relevant risks were explained, and the link to the Qualtrics survey was sent out. A reminder email with the link to the survey was sent out two weeks later, followed by a third email a week later. This study incorporated similar criteria from Con- way and Vander Vecht (2015) to quantify the criteria for tree species selection in PNW municipalities. This study differed from Conway and Vander Vecht (2015) due to the exclusive use of an online questionnaire and restricting the survey to public managers. This study incorporated additional statistical analysis beyond the descriptive statistics used in Conway and Vander Vecht (2015). 151 Two matrices were the primary focus of analysis. The first was constructed to measure tree species selection on a site-by-site basis. Respondents were asked to rank 16 tree species selection criteria: “aes- thetics,” “mature size,” “existing tree diversity,” “planting budget,” “availability,” “genetic diversity,” “maintenance costs,” “citizen preference,” “resis- tance to pests and disease,” “native species,” “soil type,” “root space,” “tree hardiness,” “water require- ments,” “hours of sun,” and “proximity to infrastruc- ture.” There were 81 responses recorded, and each criterion was ranked on a 5-point scale of 1, “not at all important,” to 5, “very important.” The second matrix was designed to measure tree species selection on a city scale; 78 responses were recorded. The following statements were used: “I strive to plant no more than 10% of a species, 20% of a genus, or 30% of a fam- ily,” “increasing canopy cover in the city I live in is important,” “my city’s street tree list strongly influ- ences what I plant,” “my city generally plants the same 3 to 5 tree species year to year,” “the tree spe- cies my city plants have changed a lot over the course of my career,” “community engagement is a critical component of my department’s success,” and “I use the tree inventory to influence the trees I select.” A 7-point scale from 1, “strongly disagree,” to 7, “strongly agree”—with the inclusion of an eighth option, “no opinion”—was used to determine manag- ers’ opinions on broader species selection. The cate- gory “no opinion” was coded as missing data because it is not on the continuous scale and would skew data. The “no opinion” response was included to reduce the number of respondents who selected a middle response when they truly did not have an opinion on the statement. Respondents were asked to categorize the status of their tree inventory. They were provided with four options: “no inventory,” “in progress,” “yes, not regularly,” and “yes, regularly.” Analysis All results were analyzed using IBM’s Statistical Package for the Social Sciences (SPSS)(IBM corp. 2016). Significance levels of ∝ = 0.05 were used for all statistical analysis. Due to small sample sizes and a lack of normality, primarily nonparametric statistics were used. This helps to reduce the influence of outli- ers, but potentially reduces the power of the statistics, and leads to a greater likelihood of type two errors. However, there were still statistically significant ©2020 International Society of Arboriculture
March 2020
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