Journal of Food, Agriculture & Environment, Vol.10 (3&4), July-October 2012 919 www.world-food.net Journal of Food, Agriculture & Environment Vol.10 (3&4): 919-928. 2012 WFL Publisher Science and Technology Meri-Rastilantie 3 B, FI-00980 Helsinki, Finland e-mail: info@world-food.net Assessment of the distribution and diversity of street tree species in Aydin, Turkey Baris Kara Adnan Menderes University,Faculty of Agriculture, Department of Landscape Architecture, South Campus 09970 Cakmar, Aydin,Turkey. e-mail: bkara@adu.edu.tr Abstract In the current study, the distribution and diversity of street-tree species were evaluated in Aydin City, Turkey, in correlation with land-use category and road-type. The study encompassed 100% of the city’s limits covering 24 neighborhoods of Aydin. Wider limits of the city were used in the study. The study was performed in 92 avenues and 74 boulevards, comprising 7 land-use categories and 3032 street trees from 24 families, 39 genera, and 53 species. The Rutaceae and Citrus genera (particularly Citrus aurantium L.) were the most common tree groups in the study area. The largest Shannon-Weiner Diversity index values were obtained in the avenues of residential areas (2.10) and boulevards of industrial areas (2.05). The largest Simpson’s Diversity index values were in the avenues (0.81) and boulevards of industrial areas (0.85). It was suggested that the number of trees belonging to the Rutaceae family in avenues and boulevards across the city should be reduced to 470 in avenues and 440 in boulevards, while the number of trees belonging to the Citrus genera should be reduced to 313 in avenues and 293 in boulevards. The number of C. aurantium trees should be a maximum of 157 in avenues and 147 in boulevards. It was also suggested that the Shannon-Weiner Diversity index value should be increased to 2.94 in the avenues of residential areas and 3.80 in the boulevards of industrial areas, while the Simpson’s Diversity index should be increased to 0.98 in the avenues and boulevards of industrial areas. Key words: Avenue, boulevard, land use, Shannon index, Simpson index, species richness. Received 10 June 2012, accepted 26 September 2012. Introduction One of the most serious problems of roadside tree plantations is the overuse of a single species; this is called the monoculture system, and increased risk of disease or damage to these important tree populations has been observed 1 . After the Dutch elm disease, scientists tried to develop formulas to help the planning process of tree plantation 2 . The 30-20-10 principle model was developed for plantation in urban areas to protect trees from disease and damage and to generate high species distribution and diversity in urban trees 3 .The 30-20-10 principle is a scale that measures the relative frequency of trees according to botanical units. Standard ecological indices are also used to define the diversity and distribution of urban trees, such as the commonly used Shannon- Wiener diversity index (SHDI) and Shannon evenness index (SHEI) 4 and Simpson diversity index (SIDI), Simpson evenness index (SIEI) 5-7 . Urban-scale studies on species diversity and distribution have been performed in parks, yet monitoring and enriching species distribution 8-11 and diversity 12-14 is important for the study of street trees. Furthermore, very few studies have been conducted on street trees in Turkey 15-18 with no existing studies focusing on street-tree diversity and distribution. In the current study, I evaluated the diversity and distribution of street-tree species on the sidewalks of 2 different road-types (avenues and boulevards) for 7 different land-use categories (residential, industrial, commercial, public, residential and commercial, residential and industrial, and public and commercial areas) at a local level (Aydin city) in Turkey. Materials and Methods This study was performed in 24 neighborhoods of Aydin City, which was delineated using a city plan obtained from the Municipality and a high-resolution IKONOS satellite image (taken on May 8, 2008). Aydin Province is located in the west of Turkey in the geographical region of the Aegean Sea, the northeast Mediterranean (27° 272 9422–27° 282 9122 E and 37° 912 7822– 37° 792 9822 N; Fig. 1). In the city, Mediterranean climatic characteristics facilitate the year-round growth of trees. Native vegetation cover is Mediterranean-type. The surface area of the city is 3273.91 ha, with 188,337 inhabitants, according to a census based on addresses in 2010. Aydin was selected for the current study because monoculture is observed in roadside plantations, and no previous study on species diversity and distribution of trees in this city has been performed. A stratified random sampling method was used to determine sample size 19 . According to the model, the city was first divided into zones at a neighborhood scale, with roads in each zone being segmented into avenues and boulevards according to traffic, pedestrian load, and road width. The number of avenues and boulevards selected for evaluation in each neighborhood was determined according to their surface area. Alphabetically ordered avenues and boulevards in each neighborhood were randomly selected and evaluated using a computer. At the final stage of the model, selected avenues and boulevards were separated into 7 categories according to the following land-use types: residential, industrial, commercial, public, residential and commercial, residential and industrial, and public and commercial. For the accurate calculation of diversity and distribution of