Modelling the distribution of medicinal plant specios of Thymus kotschyanus and Achillea millefolium using ENFA and Logistic Regression

Defining, planting and domesticating of important medicinal plants is necessary due to reducing pressure on natural resources and conserving genetic resources. Therefore, it is essential to know the factors affecting on establishment and distribution of medicinal plants. Then, the present research, is done in order to modelling the distribution of the most important medicinal plant species in the Chaharbagh rangelands of Golestan province. For this purpose, four vegetation types were selected after visiting the field of study area. In the key area of each type, sampling was done with random-systematic method. In each type three 50 m transects and on each transect 10 plots were put. Also, in order to investigating soil factors, soil sampling was done from depth of 0-30 cm, and with GPS the sampling points were registered. Some important physical and chemical soil factors such as soil texture, electrical conductivity, organic matter, acidity, Nitrogen and saturation. Topographic factors consisting ofslope, aspect and altitude were registered for each plot.In order to modelling, the models of ENFA (Ecological Niche Factor Analysis) and regression logistic were used.  The maps of environmental factors affecting on distribution of vegetation such as physiography map using DEM map and the soil maps with interpolation methods (Krijing  ، Inverse Distance Weighting and Norml Distance Weighting)inputs of model. Three important medicinal species of Thymus kotchyanus Boiss, Achillea millefolium, and Berberis integerrima were selected to analyze. Results showed that according to ENFA method, the most important factors affecting on defining utility of Achillea millefolium and Berberis integerrima habitat were altitude, soil silt and saturation while for Thymus kotchyanusBoiss these factors were altitude and soil texture. Also, the result from regression logistic model showed that, the presence of Thymus kotchyanusBoiss was directly related to altitude and inversely related to electrical conductivity, while Achillea millefolium was directely related to soil saturation and reversely related to altitude also Berberis integerrima was directely related to soil sand and altitude. In order to overlapping the maps obtained with the real vegetation map, kappa index was used. Kappa index of regression logistic model for Thymus kotchyanus Boiss ,0.57; for Achillea millefolium, 0.63 and for  Berberis integerrima was 0.67. While in ENFA model kappa index forThymus kotchyanusBoiss, Achillea millefolium, and Berberis integerrima  were 0.67, 0.75 and 0.78. Results showed that ENFA model was more precisely than regression logistic.