Changes on Canopy Cover Width and Height of Haloxylon aphyllum species Stimulated by pruning, in one of the afforested areas of Yazd Province

Wilted and dried up stands of haloxylon aphyllumspecies in afforested areas of Yazd has allways been a focal point of natural resources experts. Using various pruning treatments, the effect of pruning on the wideness of canopy cover and vigor of 12-year-old semi-trees of haloxylon aphyllumhad been evaluated formerly. That study had been conducted in two different sections of the forest in the winter of years 1994. One section had shown a tree-density of 125 semi-trees per hectare, and the other had represented a tree-density of 250 semi-trees per hectare. The treatments included cutting at different heights of 70, 35, 10 cm and also no cutting (control). The results of that previous six-year study (1994-2000) showed that pruning increased vigority and regrowth of plants treated with different levels of pruning. The 35-cm pruning treatment was preferred over other treatments. At the end of growing season of year 2005, eleven years after pruning treatments, the same trees were evaluated for the second time. Results of the new study (in 2005) showed that while non-pruning (control) 23-year-old semi-trees are wilted and almost dried up, the semi-trees with pruning are vigorous and healthy. In terms of canopy cover and height, no significant difference was found between trees with different pruning treatment in the 5 years of 2000-2005. There was a significant reduction in the canopy cover and height of non-pruning (control) semi-trees (p<0.05). For the semi-trees which had been cut at a height of 35 cm, the diameter of canopy and the height were 262 and 164 cm, respectively. This semi-trees showed a good resistance against movement of sands and sand dunes.