relationship between some environmental factors with distribution of medicinal plants in ghorkhud protected region, northern khorasan province, iran

medicinal plant species constitute a considerable part of the flora in iran and play a major role in the composition of plant communities. therefore, it is necessary to recognize the factors leading to the establishment and distribution of vegetation. for data sampling (2012), land units were specified. the plot size was determined using minimal area method and number of plots was determined by statistical methods according to the changes in vegetation cover. 120 1 m2 plots were selected and within each plot, the presence and absence of species and cover percent were estimated. the soil samples were taken in each plot in (0-30 cm) depth. data were collected and analyzed using principle component analysis (pca). results indicated that the first three axes explained the total variation. the variables of altitude, om, n, ph, and sand had significant correlations with the first axis and explained the 60% variation. for the second component, topographic properties and ec were more important traits and explained the 29% variation. these two components explained the 89% vegetation cover variation in ghorkhud region as g1 (eryngium bungei-asperula arvensis) and g2 (conium maculatum-acantholimon pterostegium) types were grown in sandy soils (low om, n, ph and high ec) coupled with high altitude and slope, g3 (asperula arvensis-cichorium intybus) type had a higher adaptability with sandy soils (low om, n and ph) coupled with lower ec, higher altitude and lower slope and g4 (artemisia sieberi-convolvulus arvensis) type tended to be established in clay soils (lower sand% and higher om, ph and n) and lower altitude.