Introduction of Suitable Rangeland Species in Habitat Soil Diversity and Different Forms of Marl Land Erosion in Semirom City

Marl lands are very sensitive to erosion in arid and semi-arid regions and are one of the most important sources of sediment production. Research has shown that there is a relationship between the geological characteristics of marls and different forms of erosion. In some marl formations, rangeland plant species have grown and stabilized which causes erosion control and soil stability. In order to better understand the status of these ecosystems, this study was conducted to identify the established plant species on marl lands and investigate the relationship between vegetation and physical and chemical properties of marl soil in three types of surface, rill and gully erosion in Semirom region.

Semirom is one of the marl regions that was selected for the current study in the classification and determination of marl erodibility indices of Isfahan province. In order to evaluate the erosion condition in three forms of surface, rill and gully erosion, BLM (Bureau of Land Management) form was completed in the same marl units and areas without vegetation cover. In the next step, three soil samples were collected from 0-20 cm depth in three repetitions in marl units including three forms of erosion. Physical and chemical soil properties including texture, EC, N, P, K, SAR, OC, CEC, CaSO4, pH, T.N.V and CaCO3 were measured. For vegetation studies in the study area, after preparing the floristic list of plant species, vegetation characteristics including canopy cover percentage and density per plant species, as well as the percentage of gravel and litter were measured and recorded. The statistical analysis of the data was done as a completely random design using SAS software and the averages of soil properties were compared according to the Least Significant Difference (LSD). Correlation analysis between soil and vegetation characteristics was also done by R statistical software.

Results and Discussion:
The results showed that in terms of erodibility, Marl lands with vegetation cover, had a better condition than without vegetation. The soil in the gully erosion was in better conditions in terms of nitrogen, phosphorus and organic matter and had better vegetation than the other two types of erosion. The results of correlation between physical and chemical soil properties and vegetation showed that the canopy cover factor was 95% and 86% correlated with the percentage of gypsum and the percentage of sand, respectively. The dominant species which showed the most protection capacity against erosion in surface, Rill and Gully erosions were Astragallus cephalantus, Cousinia cylindracea and Elymus gentry with 34.2, 33.3 and 22.05 percent of the highest combination of density and canopy cover, respectively. In terms of growth form, in all three types of erosion, forbs had the highest percentage of density and canopy cover.

The results of current research could be considered as a novel achievement in order to prevent soil erosion through establish appropriate species in marl lands with similar climatic conditions.