Journal of Rangeland

This study aimed to investigate the effects of some environmental factors on the distribution of Ferula gummosa and Ferula ovina in Shilander rangelands - Zanjan province. Two Ferula habitats were selected and their environmental characteristics were compared with control sites (no Ferula species present). Three transects with 150 meters lengths were established in each site and data were collected along the transects in seven plots of 4 m² (with 20 meters interval each). Composite soil samples from 0-30 cm of soil surface were collected from the starting point, middle and end part of the established transects and analyzed in soil laboratory. Slope percentage and direction, and elevation from sea level for all plots were also recorded. Canonical Correspondence Analysis (CCA) and Redundancy Analysis (RDA) were used to explore the relationships of Ferula species with environmental variables. According to the results, slope direction and degree, gravel and silt percentage, neutralizing substance percentage and soil saturation percentage were identified as the most important factors in characterizing Ferula species habitats. Comparing the environmental characteristics of Ferula habitats with control sites revealed that sand percentage, slope, silt percentage and elevation from sea level were different statistically between these sites (p ˂ 0.05). Logistic regression analysis indicated that soil pH (p ˂ 0.01) and neutralizing substance percentage (p ˂ 0.05) were the most important discriminating factors in Ferula habitats with the control sites.