LEAF NITROGEN BALANCE INDEX USED TO MONITOR STRESS RESPONSE TO AIR POLLUTION OF DECIDUOUS TREE SPECIES GROWN IN URBAN ZONE OF BELGRADE

Abstract

Street trees are important component of urban forest presenting a first barrier between air pollution originated from vehicle traffic and pedestrians. It implies that an improvement of air quality in urban areas greatly depends on green biomass, in short, the bigger and greener tree crown, better for human health and wellbeing. Determination of Leaf Nitrogen Balance Index (LNBI) and chlorophyll concentration (ChlC) by a non-invasive methodology and a user friendly instrument (Dualex 4, Force), widely used in agronomy and horticulture, was tested here for the assessment of tree fitness in urban zones. Investment of energy and resources either in growth or defence according to the tradeoff strategy of plants may be indicated by LNBI, which approximately presents a Nitrogen/Carbon ratio. We selected few tree species from Belgrade’s streets to determine those two parameters during summer. We also presented the changes in those parameters of the introduced bamboo species within ten years at several urban locations in Belgrade differing in air pollution aiming to evaluate usefulness the LNBI parameter in access of multiyear exposure to the effect of intense vehicle traffic. Numerous limiting factors for development of healthy tree crowns in urban ecosystem, such as low capacity to cope with toxic pollutant, sensitivity to diseases, early senescence and etc., greatly depends on tree species. We propose this methodology may also contribute in the process of choice of the adequate tree species to be planted along streets.