Growth and survival performance of Elaeagnus angustifolia and Robinia pseudoacacia in afforestation practices in arid lands of Central Anatolia

To assess the growth performance and changes in soil nitrogen two nitrogen-fixing tree species Elaeagnus angustifolia and Robinia pseudoacacia were planted in five designated afforestation sites located in the Central Anatolia Basin. Intensive site preparation included ripping the subsoil (to 80 cm) and plowing the upper soil before planting bare root (1+1) seedlings in December 2012. Two sets of five random soil samples on each experimental unit were taken in summer 2012 from the first 30 cm of the soil on 5 spots (locations) of each plot using a 200 cm3 core sampler. The same soil sampling was repeated 50 cm away from the seedling stem base in summer 2017 to gauge changes driven by the seedlings. Data from 2012 sampling were used as co-variance on the analysis of 2017 data. Initial diameter and height of seedlings were measured in April 2013 and at the end of the fifth growing season in 2017. At the end of the fifth vegetation season E. angustifolia had 80 % survival rate compared to 52% for R. pseudoacacia. Both species had an average 34 cm total absolute height growth for five growing seasons. E. angustifolia and R. pseudoacacia had also a similar absolute growth rate for diameter in five growing season. E. angustifolia had almost two times higher relative height growth and diameter increment compared to those of the R. pseudoacacia. Keywords: Arid-land, afforestation, plant nutrition, soil productivity