122 year estimate data (U.S. Census Bureau 2014). These census data were downloaded as polygon spatial data with demographic and economic vari- ables included. For most states, researchers used census places to designate candidate communi- ties. However, many TCUSA participants in the northeastern U.S. were not included in the census places data set, and so county subdivisions were included as TCUSA candidates in the following states: Connecticut, Massachusetts, New Hamp- shire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont. In these states, duplicates were removed for communities captured in both place and county subdivision data sets. A small number of counties (n = 18) and townships (n = 4) from ten other states were added to the list of candidate communities because they were TCUSA participants, but these cases were rare, so other counties and townships from these states were not considered TCUSA candidate communities. Researchers restricted the candidate commu- nity list to those communities with population ≥2,500, which is the U.S. Census Bureau’s thresh- old for an urban locale. This was done because very small communities were highly unlikely to participate in TCUSA (3.1% participation rate for communities <2,500 population). This resulted in a list of candidate communities for all fiſty states that included 11,355 communities ≥2,500 population. Among these, 2,673 communities were TCUSA participants (Arbor Day Founda- tion 2014). The candidate community spatial data (U.S. Census Bureau 2014) included ACS demo- graphic and economic data and specific vari- ables of interest are described hereaſter. A binary TCUSA participation indicator (0 = no, 1 = yes) was associated with each candidate community. Does TCUSA Participation Vary by U.S. Region? TCUSA participation rates were compared among U.S. regions. Nine regions were defined as groups of states based on U.S. Census Bureau re- gional divisions (Figure 1). Regions were used in recognition that there are differences in climatic, political, socioeconomic, and historical factors around the country that could impact TCUSA participation rates. For each region, researchers calculated the proportion of candidate communi- ©2016 International Society of Arboriculture Berland et al.: Assessment of Tree City Participation ties (population ≥2,500) participating in TCUSA. Then Pearson’s χ2 participation rates varied among regions. When the χ2 test was significant, a χ2 test was used to determine if post hoc test was used to identify which regions varied from the rest of the regions. Researchers accounted for multiple hypothesis testing in post hoc tests us- ing a false discovery rate correction (Benjamini and Hochberg 1995). Significant post hoc tests indicated a region contained either a higher or a lower proportion of TCUSA participants rela- tive to the other regions. The χ2 tests were per- formed using R v3.1.2 (R Core Team 2014). Figure 1. Tree City USA participants by U.S. region. Dots indicate Tree City USA communities over 2,500 population. Shading and numbers indicate U.S. regions. Regions were defined according to U.S. Census Bureau conventions. Is Community Population Size Related to TCUSA Participation Likelihood and Duration of Participation? Researchers hypothesized that larger commu- nities would be more likely to participate in TCUSA. Logistic regression models were used to assess whether the likelihood of TCUSA par- ticipation varied according to community pop- ulation. Separate models were constructed for the national data set and for each U.S. region depicted in Figure 1. In the logistic regression models, the dependent variable was a binary indicator of TCUSA participation, and commu- nity population was the independent variable. Community populations were log-transformed to meet model assumptions of normality. Spatial
March 2016
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
