Sexual regeneration frequency of forest species in Zagros area in relation to different ecological factors in Ilam province

In this paper, regeneration status of forest species in relation to different ecological factors was discussed. Ecological characteristics of studied regions in 110 sample plots of circular shapes, each of 500 m2 and 535 micro-plots of 2.25 m2 were investigated. Sampling was done in 4 regions within elevation between 800-2400 m above sea level and in three parallel lines on general slopes. Vertical distance between sampling units in slope direction was 100 m and overall distances between locations were 500-1000 m. Positioning of samples units were prepared with GIS and GPS. Statistical data were analyzed using EXCEL and SPSS software. Complete soil profile in center of macroplots and top soil active horizon in center microplots were studied. Results indicated that physiographical, topographical, and edaphical variation have high effects on sexual regeneration frequency in the studied area. The mean regeneration number in elevation class of higher than 1800 m, also in slope class > 60% and in northern and western directions was higher than other classes and directions. Also it was higher in Asmari formation, in rocky, coarse and sharp stones regions and in slopes. The frequency of regeneration was also higher in soil nitrogen class of 0.30-0.45 percent, in soil available phosphorus class of more than 20 mg/kg (ppm) and in soil organic matter class of 3-4.5 percent.