Effect of Motor-Vehicle Emissions on Biochemical and Morphological Characteristics Indicating the State of English Oak Trees

Abstract: Motor-vehicle emissions influence some biochemical and morphological parameters that indicate the vital state of trees in urban plantings. Twenty-eight English oak (Quercus robur) trees growing in places that differing in the level of motor emissions (10−30 m from Moscow Ring Road and the Uzkoye Forest Park in Moscow) have been analyzed for their morphological indices. In additional, the contents of proline, macroelements, and heavy metals in tree leaves and branches of different age groups (old, >100 years old, and young, 15–20 years old) has been determined. Soil samples have been taken layer by layer up to a depth of 1 m within a 2-m radius from a tree, and the total contents of Mg, P, K, Ca, Fe, Cu, Zn, and Pb, as well as the contents of mobile forms of Zn, Cu, Pb, and Fe (acetate-ammonium extract) and the concentrations of Ca2+, Mg2+, Cl–, Na+, and (Formula presented.) ions in the aqueous extracts, have been determined. According to the existing scale of the tree sanitary state and the classification of the growth and development of Q. robur crowns, the studied trees have been referred to three vital state groups: the worst (group 1), medium (group 2), and best (group 3) states. Similar levels of heavy metals were observed in branches of 100-year-old and 10- to 15-year-old trees from group 1. The contents of Zn, Fe, Ca, and S in tree branches was characterized by a strong negative correlation with the vital state of trees (i.e., the group number); in the case of leaves, such correlations were weaker or absent. The K and P contents in branches positively correlated with the life state of trees, whereas no such correlation was observed in leaves. A strong negative correlation was found between the contents of Zn, Fe, Ca, and S and the contents of P and K in tree branches; in the case of leaves, this correlation was positive. An increase in the K and P contents in leaves in response to an increase in the pollutant concentration represents one mechanism to protect the assimilation apparatus from the impact of motor-vehicle emissions. © 2021, Pleiades Publishing, Ltd.