A preliminary study on the possibilities to indicate the effects of urban stress on maple trees

Urban trees have an important role to create a more livable environment. These plants are exposed to various types of environmental stresses that might cause decline in their condition and decorative value. The aim of our preliminary study is to study the effects of urban stress factors, mainly the air pollution and pest damage on maple trees. Three maple species were studied: field maple (Acer campestre), sycamore maple (A. pseudoplatanus) and Norway maple (A. platanoides) in four areas in Budapest, Hungary with different traffic density. The peroxidase (POD) enzyme activity was measured in the leaves by a spectrophotometric method. Phytophagous insects with piercing-sucking mouthparts (Hemiptera) were also collected from the canopy level by beating method. We found that POD activity was generally the highest in field maples and the lowest in Norway maples with sycamore maples between, but we did not find consistent patterns at each sampling site. The abundance of the collected hemipterans showed similar pattern, but showed no consistent tendency at the various sampling sites and therefore, the abundance of hemipterans did not explain the variation of POD activity. In our study the connection between the POD activity, the air pollution and the abundance of hemipterans remained not fully understood. To clarify this relationship further studies are required