Variation in Physico-chemical Properties of Soil in Different Natural Habitats of Rangeland Medicinal Species:Salvia macrosiphon Boiss

Soil erosion has been increasing in Iran in the last decade due to the lack of optimal use of pasture and forest lands. This factor destroys the ecological conditions suitable for the life of organisms while wasting the soil and producing sediment. Preservation and development of vegetation in pastures, such as medicinal plants, plays a significant role in preventing soil erosion. Salvia macrosiphon Boiss is a perennial species and has an essential oil plant of the Lamiaceae family, which is traditionally used in the treatment of respiratory diseases, depression and urinary tracts. Considering that in recent years, due to the economic and export value of this species, its natural habitats have been overexploited, and also due to climate changes and extensive droughts of the past few years, as well as harvesting in this way, the process of soil erosion in its natural habitats has been accelerated. Therefore, the present study was conducted with the aim of investigating 19 ecological attributes of the main habitats of S. macrosiphon in Fars and Hormozgan provinces.

In the current study, the natural habitats of this species were determined by using Flora Iranica and with the assistance of Hormozgan Agricultural Research, Education and Extension Organization experts. Characteristics of five habitats in Fars province (including Kazeroon, Farashband, Dehram, Evaz and Jahrom) and three habitats in Hormozgan province (including ZahedMahmoud, Bekhan and Sirmand) were studied. The climatic features of each natural habitat such as latitude and longitude, altitude, mean annual temperature, minimum and maximum temperature, and mean annual precipitation were recorded. From each habitat, three soil samples were taken from a depth of 0-30 cm. The percentages of clay, silt, sand, pH, electrical conductivity (EC), organic carbon, absorbable phosphorus, absorbable potassium, total nitrogen, calcium carbonate equivalent (CCE), absorbable iron, absorbable zinc, absorbable manganese and absorbable copper were measured. To analyze the studied environmental factors and the measured soil parameters, the multivariate analysis method including Pearson correlation coefficient of traits, decomposition into principal components and cluster analysis was used by SPSS ver. 26 software.

The results revealed that S. macrosiphon was distributed at an altitude of 400 to 1550 meters above sea level in Kazeroon, Farashband, Dehram, Evaz, Jahrom, ZahedMahmoud, Bekhan and Sirmand natural habitats and on the slope between 0 to 20%. The maximum and minimum annual rainfall were recorded as 156.2 and 387.7 mm, respectively. The average annual temperature was recorded at 24.5 °C and also, the minimum and maximum temperatures were -3.8 and +49.5, respectively. This species grows in the loam, sandy loam and silt loam soil textures with a pH of 7.7-8.4, an EC of 0.47-6.87 dS/m. Furthermore, it was found that S. macrosiphon was spread in non-saline and saline soils (electrical conductivity 0.47 to 6.87 dS/m). The soil in which the species was grown in the studied areas was poor in terms of available potassium content (46 to 302 ppm). The highest concentration of absorbable Fe (6.7 mg/kg) in Farashband habitat, absorbable Zn (3.8 mg/kg) in Kazeroon habitat, absorbable Mn (0.28 mg/kg) in Kazeroon habitat and absorbable Cu (0.2 mg/kg) was observed in Zahedmahmoud habitat. On the other hand, the lowest concentration of absorbable Fe (1.5 mg/kg), absorbable Zn (0.6 mg/kg) and absorbable Mn (3.3 mg/kg) was observed in Dehram habitat. Also, the lowest amount of absorbable Cu (0.3 mg/kg) was obtained in the two habitats of Dehram and Evaz. Using cluster analysis, habitats were divided into four clusters according to which habitats with common characteristics were placed in the same group.

The findings of this study showed that S. macrosiphon is resistant to hot and dry conditions. The two habitats of Dehram and Zahedmahmoud are prone to flooding due to the high percentage of silt in the soil texture. A high percentage of silt increases soil runoff during rainfall because the silt texture of the soil is one of the factors that prevents water from penetrating the soil. If the percentage of silt in the soil texture is high, the soil can absorb less water, and as a result, more water flows during rainfall, which can lead to soil erosion. The lack of absorbable phosphorus and potassium, as well as the lack of nitrogen and organic carbon, are the most obvious attributes of the soil of the S. macrosiphon habitats, which may cause limitations in its growth. The parent material of the soils of the studied areas originates from calcite limestone. In areas where the soil is calcareous, the temperature and pH are high. Based on the estimated Pearson correlation coefficient between the traits, it was determined that the higher organic carbon soil will have the higher amount of nitrogen. The presence of organic matter and the amount of nutrients have a direct relationship. This means that wherever the amount of organic matter is higher, the amount of nutrients is also higher. On the other hand, an increase in temperature leads to a decrease in soil organic matter. The results of analysis into the main components led to the extraction of five factors, which, according to the effectiveness of the variables, the selection based on the first component will lead to habitats with heavier soil texture and higher potassium concentration, which can provide a possibility of pasture development by this species in soils with a higher clay content and wide range of temperature fluctuations. In general, this research demonstrates considering the importance of S. macrosiphon in terms of being an under-expected pasture and medicinal species, as well as taking into account limitations such as low rainfall, and irregular spatial and temporal changes. Due to (limited) rainfall, high evaporation and transpiration and unprincipled exploitation, the condition of the habitats is extremely fragile and will lead to the instability of these ecosystems. By planning and conducting optimal management of pasture and medicinal resources through the obtained information, it is possible to domesticate and cultivate this plant by following the microclimatic conditions of this plant and providing natural conditions for its growth and protecting its valuable genetic resources. After all, these studies help us to be able to use optimal methods to improve and preserve the soil and prevent its erosion through plant preservation.