The effects of density and pruning levels on survival and vigority in Saxaul (Haloxylon aphyllum Minkw.) plantations of Yazd province

The determination of survival and vigority effective parameters on old saxaul (Haloxylon aphyllum) shrub is essential for sustainable development of planted forests in desert area. In fact, the objective of this study was to determine the effects of different density and pruning levels on survival and the vigority of saxaul. The study was carried out in obviously wilted planted saxaul forest that is located in Ashkezar desert region of Yazd province. Experiment was conducted in split plot design with main-plots that had 250 and 125 trees per ha and sub-plots were 3 types of pruning at height of 10, 35 and 70 cm above ground surface, plus control (no pruning) sub-plot. Pruning was done on autumn 1994. After one year from shrubs pruning, analysis of plant mortality percentages was started and continued on the same pruning time to 2000. The determination of vigority carried out only in 2000. Results showed that the differences of survival among all treatments were not significant. The effect of density on vigority was also not significant, whereas the pruning height had significant effect (p<0.01) on vigority of saxaul shrubs. One can conclude that the best pruning method was cutting 35 cm above ground with vigority of 43.3% and 40.9% in 250 and 125 trees per hectare treatments, respectively.