The role of light intensity on survival of Quercus branti saplings in relation to aspect and distance from seed trees in Ilam province forests

This research was conducteded to assess sunlight effects on survival of the Persian Oak (Quercus brantii) saplings، based on randomized complete block method in the form of split plots، during a 3 years period with 3 replications. Tow 2 factors and 8 treatments were considered in the design. The first factor was aspect that divided in 2 levels (N and S). The second factor was distance of saplings from seed trees that divided in 4 levels، which were near، intermediate، far and control plots. Afterwards، average survival of oak saplings was compared in 3 classes of relative light and then correlation between relative light intensity and percent survival was investigated in the whole plots. The results showed that the mean survival was 20. 9% in the northern aspect، 22% in the southern aspect and 21. 4% in the total plots. The maximum and minimum saplings survival were 77. 8% (one of the plots near the seed tree) and 0% (one of the control plots) respectively. The maximum، minimum and average relative light in sub-sub plots and in control plots were 95%، 1% and 58. 5% respectively. Also، the results of statistical analysis showed that the differences of saplings survival for both treatments of aspect factor were not significant. Except the correlation between Level 3 of second factor (the most distance of saplings from seed trees) and control treatment، the correlation between other levels of distance factor، were significant at 1% level. In this context، function of survival was better on the close plots from the seed tree than middle plots and also on middle plots than far plots. There was a negative linear relation between relative light intensity and survival of saplings (R2=69%). So we can conclude that survival of oak saplings is decreased with increasing distance from tree crown (Thereby increasing light intensity). Also، planting saplings are recommended only in plots close and middle distance to the seed trees.