Investigating on the relationship between plant measurements of Parapholis incurva with environmental factors and water point distance in rangelands of Incheh Borun Golestan province (case Study: Incheh Borun)

Introduction Analyzing the shape of the response curves is necessary to advance ecological theory. The purpose of present study was to investigate the most important environmental factors affecting on presence of Parapholis incurva by using the HOF function In the rangeland Inchehboroun from Golestan province.

Towards this attempt 200 quadrates of 4m2 along water point distance were taken. The sampling method was randomized-systematic. In the area sampled, presence of Parapholis incurva species, was recorded. In addition to identifying plant species, the presence and absence of any species in the region were mentioned. In the center of each plot, the soil was sampled from depths of 0 to 20 centimeters .Soil samples were transferred to the laboratory and experiments were carried out to measure pH, EC, soil texture (silt, clay and sand), organic carbon, nitrogen and phosphorus. In this research pH, EC, soil texture, organic carbon, nitrogen and phosphorus were measured using pH meter, conductivity meter, hydrometric method and Olson method, respectively In order to study the shape of response curve in relation to the mentioned variables, HOF model was used with binomial distribution function.Huisman-Olff-Fresco (HOF) models The data were analysed by R ver.3.0.2 computer porgramme.

The results showed that the ecological amplitude and optimum along water point distance gradient for Parapholis incurva has been recorded 350-1000m and 765 m respectively . The results showed that the P. incurva has reached the maximum frequency in (765 m distance from the water source, , bulk density 0/9 g / cm3, EC 21.4 ds / cm, organic carbon 0.9%, sand 19.9% Clay 22.02%, and silt 46%,).

In general, in the Inchehboroun rangeland the extent of the ecology and the probability of the presence of the P. incurva increased by taking the water point distant