Qualitative and Quantitative Indicators of Foliar Mass of Woody Plants in Urban Greenspaces According to the Level of Air Pollution

The purpose of this study is to conduct a comparative analysis of the leaf fall timing and parameters of fluctuating leaf asymmetry among two commonly used plant species for street landscaping in Detroit city, namely, American elm and American ash. The study was completed between summer and fall for the year 2019 in and around Detroit, US. Phenological leaf fall timing of elm and ash was studied, and the fluctuating asymmetry index of their leaves was estimated within the city limits (80 trees of ash and 40 of elm) and outside the city (control site, 20 trees of each species). Leaf fall in city ash trees was recorded from November 1st to 4th and 5-8 days prior to the leaf fall in elms (p ≤ 0.01). Elm trees in the control group shed their leaves 10 days later compared to the city trees, i.e., on average, on November 25th (p ≤ 0.01). Ash trees in the control group shed their leaves earlier than the elm control group, on November 11th (p ≤ 0.001). In the city streets, the average fluctuating asymmetry ranged from 0.065 to 0.086 (point 1), from 0.049 to 0.078 (point 2) and from 0.063 to 0.082 (control site, near the highway).