Arboriculture & Urban Forestry 38(3): May 2012 Table 2. Street tree parameters used to estimate impact of EAB in eastern Canada. City Provincez Bathurst Barrie Bracebridge Chatham Fredericton Guelph Halifax Huntsville Kitchener London Meaford Moncton Oakville Owen Sound Parry Sound Sault Ste Marie St. Johns South Porcupine Sudbury Thunder Bay Timmins Toronto Averagex NB ON ON ON NB ON NS ON ON ON ON NB ON Ottawa - Gatineau ON Oromocto NB ON ON ON NFLD ON ON ON ON ON Data sourcey S G S S, G S S, G P S G S S S P G S S S S P S S G S P Trees/km road 84.4 100.4 185.7 115.9 123.0 112.7 - 164.4 95.7 97.1 120.8 72.1 - 115.5 149.3 106.2 50.5 91.4 - - 59.0 76.8 124.0 - 107.6 % Ash 4.0 - 0.0 - 0.0 6.3 0.4 1.5 - 3.3 8.2 0.1 9.2 - 0.4 6.7 19.8 2.2 7.8 1.7 4.9 - 0.4 7.8 6.0 % Ash <5 m tall 0 - - - - 8.1 - 0 - - 12.5 - - - - 23.1 35 5.9 - 0 - - - - 10.4 z NB = New Brunswick; ON = Ontario; NS = Nova Scotia; NFLD = Newfoundland. y S = street tree survey; G = Google Maps; P = published values. See text for complete details. x Average is weighted by population size of urban areas. m of city streets. This was done for a total of 150 randomly lo- cated 0.5-km street segments across six Ontario cities (Table 2). During this process, several other pieces of information were gathered. First, to estimate impacts in residential backyards, the number of trees in backyards were counted along the same 150 random street segments used to count street trees (Table 2). In cases where houses backed onto woodlots, making prop- erty lines difficult to distinguish, only trees within 10 m of the woodlot edge were counted, as these would have a higher likeli- hood of being treated or removed in the case of an EAB attack. The ratio of street trees to backyard trees was 1:1, suggesting that street tree costs could be doubled to include the backyard component. However, not all streets are fronted by dwell- ings with backyards (i.e., some are fronted by parks, industrial parks), thus the percentage of urban roads fronted by residen- tial dwellings at the same 150 road segments was also estimated. Based on these estimates, backyard tree impacts are expected to be about 68% of those associated with street trees (Table 2). Estimating Urban Ash Component in Western Canada Different data sources were available for provinces in western Canada (e.g., Manitoba, Saskatchewan, and Alberta). The For- estry Branch of Manitoba Conservation provided a GIS database of an ash inventory that had been carried out for 16 urban cen- ters in Manitoba. To make these data comparable to the street tree data for eastern Canada, the study authors selected only trees within a 10 m buffer of the road system in each community. Each tree in the database had a height attribute, and so were classi- fied into the same height classes as those outlined for eastern Canada. The number of street ash per kilometer of road was cal- culated for each of the 16 communities by summing the number of street trees in each size class and then dividing each total by the length of the urban road system in that community (Table 3). Due to a lack of comparable data from other western provinces, these values were applied to Saskatchewan and Alberta as well. There were notable differences in the relative abundance of ash in eastern and western Canada. In western Canada, there was an average of 8.7, 20.2, and 32.9 street ash/km in the small, me- dium, and large size classes, respectively (Table 3); comparable numbers for eastern Canada were 1.6, 2.5, and 2.2 street ash/km (calculated from Table 2). This approximately 8× higher inci- Table 3. Number of small, medium, and large ash trees per kilometer of urban road for 16 communities in western Canada. Urban area Manitou Treherne Altona Beausejour Carberry Carman Dauphin Deloraine Rivers Selkirk Souris Steinbach Stonewall Virden Winkler Province Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Manitoba Portage La Prairie Manitoba Averagez Ash trees per km of urban road <5 m tall 5–10 m tall >10 m tall 0.1 11.1 10.6 6.3 6.7 21.6 2.6 26.4 8.8 3.9 11.5 9.5 7.6 9.0 23.0 2.8 8.7 z Average is weighted by population size of urban areas. 36.3 31.2 35.6 8.7 22.3 19.3 13.6 30.7 4.2 10.0 27.7 24.3 7.7 11.2 48.7 13.6 20.2 38.0 46.6 51.2 16.1 36.5 49.2 18.4 66.8 16.6 15.1 44.7 39.8 16.3 23.0 79.6 19.0 32.9 100 - - - - 16.2 - 0 - - 25.0 - - - - 46.2 25 28.2 - 36.3 - - - - 34.6 83 % Ash 5–10 m tall % Ash >10 m tall 0 - - - - 75.7 - 100 - - 62.5 - - - - 30.8 40 65.9 - 63.6 - - - - 54.8 1.08 - 1.0 54.4 - 67.5 Ratio of backyard to front yard trees - 0.95 - 0.75 - 1.21 - 0.98 - 1.05 - - % house frontage - 60.3 - 62.7 - 82.7 - 74.1 - 68.6 - - ©2012 International Society of Arboriculture
May 2012
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