Journal of Rangeland

The present study was conducted to study the response curves of Aeluropus lagopoides and Salsola turcomanica along some environmental gradient using HOF function in Inchehboroun rangelands in Golestan province. A randomized-systematic method was used to collect the species occurrence data in four hundred quadrates with size of 4m², placed along a gradient from watering point. Soil samples were collected from 0-20 cm in all quadrates and their bulk density, soil moisture, pH, N, EC, P, organic carbon, sand, silt and clay content were measured. HOF model with binomial distribution function was used to explore response curves of the species to these soil variables. The data were analyzed by R _ver.3.0.2 computer programmer. Results revealed that ecological amplitudes of A. lagopoides and   S. turcomanic differ considerably. According to the results, the occurrence range and optimum condition for A. lagopoides were 320-1000m and 874m from watering point respectively. The occurrence range and optimum condition for S. turcomanica occurrence was 200-1000m and 845 m from watering point respectively. A. lagopoides and   S. turcomanica response curves to watering point distance and pH gradient had increasing and decreasing monotonically trend respectively. The ecological optimums along the pH gradient were 7.5 and 7.7 for A. lagopoides and S. turcomanica respectively.