Arboriculture & Urban Forestry 37(2): March 2011 preparation costs for replacement trees include tree and stump removal costs if replacements are needed. These costs are a func- tion of local economies. Costs associated with the complete loss of the community ash resource in these states were assessed, based on the impact of the bronze birch borer (Agrilus anxius Gory) (a native buprestid) on exotic birch as contrasted with na- tive birch in Ohio’s Shade Tree Evaluation Project (Herms 2002). MATERIALS AND METHODS State urban foresters in Michigan, Indiana, Illinois, and Wis- consin were asked to provide contact information for indi- viduals responsible for managing their respective commu- nity’s urban forest, including but not limited to Tree City USA communities. The first request was mailed in January 2009 with subsequent mailings conducted as state urban forest- ers provided lists for their respective states until April 2009. It was assumed that the individuals identified by the state for- esters had a reasonable understanding of their urban tree char- acteristics, as well as knowledge of community demographic information available from internal records and/or secondary sources, such as the U.S. Census Bureau. In the previous study of Ohio (Sydnor et al. 2007a), this method (based on collection of primary data from communities) resulted in comparable esti- mates of the number of urban ash trees in the state to that pro- vided by Kovacs et al. (2010), who used FIA data to give ash density per hectare and the 2001 National Land Cover Database to identify and quantify the area of tree canopy in urban areas. Materials and methods in this paper generally follow those set forth in Sydnor et al. (2007a), including the questions asked on the survey instrument. As discussed there, in order to com- pare responses of small communities with responses of large communities, ash tree data was normalized by population; street, park, and private tree numbers as reported by the com- munities were multiplied by the percentage of ash reported to get the number of street, park, and private ash trees. These numbers were then divided by the community’s population in thousands to give the number of street, park, and private trees per 1,000 residents. Communities were instructed to report in- formation they were comfortable in reporting (i.e., for which they at least had estimates). Generally, respondents felt most comfortable in estimating street trees; as a result, the number of communities reporting data varied by category. Outliers did create some skewing in the data that resulted in differences be- tween mean and median values, which will be discussed later. Given that the prices used in Sydnor et al. (2007a) were based on Ohio data, tree removal and stump removal costs were determined using a survey of Tree Care Industry Associa- tion (TCIA) members in the four study states in the winter of 2009/2010. TCIA represents private tree care contractors and arborists. Members were asked for tree removal and stump re- moval costs for five size categories. Respondents were told to assume the tree was readily accessible and not encumbered by proximity to buildings or utilities. Actual prices for a given site might be two to three times higher due to encumbrances. TCIA members also were asked to report the species ad- justed basic price for 35 cm ash trees using the trunk formula method procedures set forth in Guide for Plant Appraisal (CTLA 2000) or the national guide. Location and condition val- ues were determined as suggested by the national guide in that RESULTS AND DISCUSSION Sample description A total 123 communities of the 586 contacted across the four states responded, for an overall response rate of 21% (Table 1) after two e-mail surveys and one mail survey. Such a response rate is com- mon to survey research, especially to surveys without extensive follow-up (Malhotra 1996). Responding communities represent- ed 3,549,246 citizens or 10.5% of the four-state census population of 33,802,345 individuals, as of the year 2000. By comparison, cities used by Kovacs et al. (2010) in the four states included sev- en cities: Chicago, IL; Indianapolis, IN; Livonia, MI; Milwaukee, WI; Palatine, IL; Troy, MI; and Urbana, IL. The smallest com- munity was Urbana IL, with a population of nearly 39,000, while the break between large and small communities in the current study was 10,000. The average household income of responding communities was $57,383, and the median of responding com- munities was $50,000. These values are consistent with the 2007 Table 1. State and total response rates plus population estimates based on 2000 Census data. State IL IN MI WI Overall Number of Response Proportion of responses 40 6 25 50 123z rate (%) 20.9 22.2 21.2 20.0 21.0 z State was unknown for two responses. national median income of $50,740 (U.S. Census Bureau 2000). Number of Ash Trees in Midwest Communities Data were aggregated from respondents across the four states for analysis. This was justified in several ways. First, the four states included in the study (Indiana, Michigan, Illinois, Wiscon- sin) are contiguous and well within the natural range of white ash (Fraxinus americana) and green ash (Fraxinus pennsyl- vanica), respectively (Burns and Honkala 1990). Second, the ashes (Fraxinus spp.) make up a similar but minor component of each states respective growing stock volume, ranging from 4.9% in Michigan to 7.5% in Indiana in 2007 (USDA Forest Service). Lastly, there was not a statistical difference among the states for total ash per 1,000 residents, summing street, park, and private ash trees (p = 0.11) based on a Kruskal-Walis test. A separate analysis determining the total number of street, park, and private ash trees by using individual state population and ash densities, and then summing across states to reach a grand total, generally resulted in comparable estimates to the ag- ©2011 International Society of Arboriculture 6.9 6.3 23.4 10.5 Population population (%) (2000 Census) 9.4 12,419,660 6,080,485 9,938,492 5,363,708 33,802,345 85 the first author had previously visited a number of communi- ties to develop an average value for location (60%) and condi- tion (70%). Park trees were, in general, farther from structures or human activity and more likely to be in groups; thus, loca- tion values for park trees were estimated at 50%. Finally, TCIA members were asked to report the replacement costs for a 5 cm tree for their community. Note that sample sizes for indi- vidual states were sometimes small, especially for basic prices.
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