Biodiversity of Woody Species in Relation to Topographical Factors in Central Zagros Forest Ecosystems

In this article the most important indices of diversity and richness of woody species, in relation to three physiographical factors, including altitude, aspect and slope have been discussed. For this purpose, ecological characteristics in 330 circular 500 m2 plots, were studied by systematic random method. Vertical distance of sampling units was 100 m above sea level. Sampling in 4 different areas, in range of 800-2400 m elevation was performed. Map Position plots was produced by the GIS and GPS systems. Results showed that statistically difference between classes of each topographical factor, in relation to the indices of diversity and species richness was significant. This study in relation to Simpson indices in altitude factor, showed that the difference between first class (800-1300 m) and third class (up to 1800 m) is exceptionally significant, In the other indices, difference of first class to third class and second to third, was significant. In other hand, diversity and richness indices of class in high altitude were more than other classes. Average of all indices in the northern aspect was higher than south and flat areas. Results of Shannon and Simpson diversity indices to slope factor, showed that first class slope (0-10%) compared to third (30-60%) and fourth class (up to 60%), and second class slope (10-30%) compared to fourth class slope, were statistically significant. Moreover, average species richness indexes in low-slope land (0-10%), compared to areas with slope over 30% (third and fourth classes), were higher. Therefore, it can be seen that the species diversity indices, in areas of low slope are higher than high slope areas, and about the species richness indices, are opposed to this case. This is due to that diversity indices values are decreased by a decrease in the canopy in studied areas of low slope. Due to the relative increase of the presence of woody species in the low slope areas, the species richness indices have been increased to some extent.