Identification of Physical and Chemical Soil Factors Effects on Medical Plants Distribution with Use Ordination Method (Case Study: Deraseleh Rangeland, Savadkouh, Mazandaran Province)

Plants distribution in nature is not by chance, but it is a function of various factors such as topographical, edaphic, climatic, anthropogenic factors, etc. Environmental factors along with management factors play an important role on the species composition and richness. In fact, there is a high correlation between the establishment of plants and environmental conditions, so that the composition and structure of plant communities largely influenced by environmental factors. In particular, soil and its numerous properties play a significant role in the establishment of plant species. These facts show the importance of medicinal plants and their influential environmental factors and state that such studies are necessary in all fields of natural resources. Therefore, this study was aimed to determine the region plant communities and their medicinal plant species, and to identify factors affecting the establishment of these communities using ordination method. Considering the region conditions, its pristine nature, the high population of exploiters, and lack of basic information about vegetation, this study can also be effective in improving economic and social conditions of the region residents.

The study area basin is mountain rangelands of Deraseleh that is located in one of sub basins of Talar River (one of the major Caspian Sea sub basin) in Mazandaran Province. For random-systematic sampling, the 50-meter transects were randomly laid out in the region and 5 plots were systematically established along each transect with 10 meters interval. Therefore, a total of 60 transects and 300 plots were sampled. Soil samples were taken in the middle of transects from 0–30 cm depth. Soil samples was transferred to the laboratory to measure soil properties including soil texture, electrical conductivity (EC), acidity (pH), nitrogen (N), phosphorus (P), calcium carbonate (CaCO3) and potassium (K) and organic carbon (OC).After data normalization, DCA that is an indirect ordination method was used to identify changes in plant composition and to determine gradient length. As gradient length was more than three, CCA that is a direct ordination method was selected for assessing the vegetation and environmental variables relationships.

The region flora consists of 94 plant species belonging to 79 genera and 29 plant families. Considering medicinal plants, 29 species were dominant in the region and Lamiaceae family with 13 species had the frequency in the region.DCA analysis showed that the importance of axes decline to the forth axis on the basis of Eigen values. Based on the gradient length and Eigen values, CCA was used to determine the effect of soil factors on medicinal plants. Different soil factors had significant effects on species distribution. Each of soil properties controls the distribution of the species to a certain extent. CCA analysis showed that the effect of environmental factors on vegetation is meaningful (P=0.001; F=1.68). Generally, some species were affected by a variable but some by several variables. Some species did not show significant correlation with soil properties.

Knowing about environmental factors controlling vegetation can optimize management of rangeland ecosystems that helps farmers to utilize their land sustainably. Identifying medicinal plants and understanding their controlling factors can be effective in determining management practices. In this study, ordination techniques showed that plant species belonged to the same family or genus are not necessarily influenced by the same environmental factor. For example, two species of Ferula were influenced by different factors. Soil texture and pH had somewhat more effects than other variables on vegetation. Soil properties had negligible effect on some species such as Senecio vulgaris and Vaccaria liniflora. It can be suggested that other factors such as topography and management may be effective on this species. In conclusion it must be said that, the ecological needs must be identified for optimal utilization of forage and medicinal species and species with use in industry. Then, proceed to the cultivation and exploitation of plant species according to controlling environmental factors.