Cold hardiness of some native and exotic cedar (Cedrus spp.) taxa sampled from Istanbul-Atatürk Arboretum

In this study, the seasonal frost resistance of Atlas cedar (Cedrus atlantica), Himalayan cedar (Cedrus deodara), and Taurus cedar (Cedrus libani) species located in the Istanbul-Atatürk Arboretum was determined. For this purpose, shoot samples obtained from the species were exposed to 10 different low-temperature levels in November, February, and March. In November and March, the shoots were subjected to temperature levels of control, -5, -7.5, -10, -12.5, -15, -17.5, -20, -25, and -30 °C, while in February, they were subjected to temperature levels of control, -5, -10, -15, -17.5, -20, -22.5, -25, -27.5, and -30 °C. Damage to the shoots after the application of low temperatures was determined by chlorophyll fluorometer (CF) and visual assessment (VO) methods. From the obtained findings, the temperature gradients at which the species were damaged by frost (LT50) were calculated using a nonlinear regression model. According to the CF and VO methods, the frost resistance levels (LT50) of the species were determined as follows: In autumn, -15.4 °C and -15.7 °C for Atlas cedar, -13.1 °C and -13.0 °C for Himalayan cedar, and -15.5 °C and -15.6 °C for Taurus cedar; in winter, -19.7 °C and -19.9 °C for Atlas cedar, -16.8 °C and -16.6 °C for Himalayan cedar, and -21.0 °C and -20.8 °C for Taurus cedar; in spring, -18.0 °C and -15.5 °C for Atlas cedar, -14.7 °C and -14.3 °C for Himalayan cedar, and -18.0 °C and -17.9 °C for Taurus cedar. Based on the findings, Taurus cedar was found to be the most frost-resistant species among the three, followed by Atlas cedar. Himalayan cedar was identified as the least frost-resistant species. As a result of the research, it can be recommended that Taurus cedar should not be used in afforestation projects, particularly for urban and landscape purposes, in regions where temperatures fall below -20.9 °C, Atlas cedar below -19.8 °C, and Himalayan cedar below -16.7 °C.