Assessing and comparing composition and diversity in urban trees populations in Northern Italy

Scarce research exists on urban tree diversity and species composition drivers for urban forests in Italy. Data from complete urban forest inventories conducted over the last 5 years in cities of different sizes in coastal and inland areas of northeastern Italy have been used to assess and compare street and park tree populations. The main aim of the study was to identify differences in species composition and diversity between tree populations according to urban size (cities ranging from 10,000 to 300,000 inhabitants), geographic areas (coastal versus inland), and types of tree population (parks versus streets). The most commonly used diversity descriptors such as Shannon-Wiener diversity index, Inverse of Simpson Index of diversity, Maximum equitability and Equitability species indeces were used in the analysis. Data from the inventory included not only taxonomical but also structural data, and in particular DBH; therefore tree age classes were also considered in studying possible trends in species selection throughout time (prior to 1970, between 1970 and 1990, and after 1990), and in identifying possible drivers of species choice in urban planting and how these have changed over the past sixty years.