Arboriculture & Urban Forestry 46(2): March 2020 87 Figure 2. Location of plots. Source: Google Maps. square (also called Plaza de Armas)(T13 – T20). The third area is the street named 1st South (Uno Sur), which is the principal commercial zone of the city and has the least densely populated area of trees of the three areas considered (T21 – T30)(Figure 2). For each plot, the percentage of tree coverage was obtained by horizontally projecting the tree crown from the trees inside the plot. During autumn 2016, the tree coverage was measured, showing that leaf loss in deciduous trees accounted for a 40% reduction in tree coverage on average. The percentage tree cov- erage (C) was found and split into five classes from 0% to 100%: 20% if C ≤ 20%, 40% if 20% < C ≤ 40%, 60% if 40% < C ≤ 60%, 80% if 60% < C ≤ 80%, and 100% if C > 80%. This discretization was performed so that the ANOVA could be used with the data. Environmental variables were recorded at two points in each plot, at the center and at the edge, cor- responding to: (a) particulate matter PM10 at a height of 1.5 meters and measured in mg/m3 recording maximum PM10 (PM10 PM10 (PM10 (10.0 µm) , max) and average avg), using the measurement instrument DustTrak II Model 8532, TSI; (b) temperature at ground level (T° ground) and at a height of 1.5 meters (T° 1.5 m) was measured with a thermo hygrometer JT-07CRL in degrees Celsius; (c) relative humidity at a height of 1.5 meters, measured as a percentage (%) and using the same instrument as was used for mea- suring the temperature; (d) levels of noise measured in decibels at a height of 1.5 meters (dBA), maximum (Max noise), and minimum (Min noise), measured with a sound level meter using the measurement instru- ment LUTRON SL-4012; and (e) ultraviolet radiation at a height of 1.5 meters and measured in nanometers (nm) using the measurement instrument Light meter UV340B. The measurements were recorded during three different times of day: (i) between 8:00 and 9:00 am; (ii) between 2:00 and 3:00 pm; and (iii) between 7:00 and 8:00 pm, corresponding to times of day: morn- ing, midday, and evening, respectively. In each hourly period mentioned, the 10 sites in each block were vis- ited to measure the different variables. The season when measurements were made corre- sponds to the date ranges: November 2014 to January 2015, April to May 2015, and September to Novem- ber 2015, which we have termed summer, autumn, and spring, respectively. The total number of records was 1,968, which is equivalent to 15,515 points of data. To record the data, two ad hoc data collection forms were created, one for the measurements of ©2020 International Society of Arboriculture
March 2020
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