Comparison of some physical-chemical properties of soil under the canopy of two plant species, Amygdalus scoparia spach and Seidlitzia rosmarinus, and outside the canopy in Bajestan rangeland of Khorasan Razavi

Background and objectives: In recent years, ecologists have paid special attention to plant-soil feedback as a driver of plant community dynamics, especially in the context of succession, plant invasion, and ecosystem processes such as the nitrogen and carbon cycles. Plants alter the physical, chemical, and biological properties of the soil environment. Changes in soil properties lead to changes in plant function and responses to each other, ultimately leading to changes in the composition and diversity of the plant community. By altering the physical, chemical and biological nature of their soil environment, individual plants have the ability to influence their performance relative to their competitors, ultimately leading to changes in plant community composition and diversity. The impact of plant species on soil resources and their biogeochemical processes is one of the important ecological phenomena, especially in arid and semi-arid regions. The relationship between plants and soil is a fundamental factor in land management and planning. Plants affect the soils under their canopy and cause non-uniformity of soil properties at different distances. The purpose of this study was to investigate the effects of two species of Amygdalus Scoparia Spach and Seidlitzia Rosmarinus (Ehreb)Bge on some physico-chemical properties of the rangelands of Bajestan. The S. rosmarinus plant has created Nebka hills due to the stabilization of loose sand between the branches and leaves of the S. rosmarinus plant, and the formation of these hills is a very important factor in controlling sandstorms. The branches of this plant are grazed by large livestock such as camels, and for this reason, the Seidlitzia rosmarinus rangelands are very suitable pastures for raising camels. A. scoparia grows in deep and semi-deep, gravelly soils and on calcareous-siliceous formations on gentle slopes of the mountains. The mountain almond shrub is one of the country's resistant and native species to harsh environmental conditions and water shortages, making it suitable for the hot climate of Khorasan, Tehran, Yazd, Chaharmahal and Bakhtiari, Sistan and Baluchestan. This species has an altitude index of less than 2000 meters, but of course it also reaches higher altitudes in hot and dry mountains. In recent years, mountain almond shrubs have suffered from desiccation and, despite easy regeneration, have been threatened by wood-eating pests in some areas such as the south of Khorasan province.
Materials and methods: The rangelands of Bajestan, Khorasan Razavi are located in arid and semi-arid regions, and two species of A. scoparia and S. rosmarinus are the dominant plant species in the region that are used in improvement and development plans. Therefore, it is necessary to investigate the extent and type of impact of cultivation of these two species on the soil under the canopy and in open space. To conduct the research, after determining the habitat of the A. scoparia and S. rosmarinus plants, 5 samples were taken from the soil under the canopy of the plant bases for each plant from a depth of 0-50 cm of the soil surface (considering the rooting depth of the two species mentioned and the location of the two species) and also from the soil of the control area (with an appropriate distance from the canopy of the two plants in question) in a completely random manner (a total of 20 soil samples). For each soil sample, physical properties including soil texture, rock and gravel density, as well as chemical properties including acidity, salinity, total nitrogen, organic matter percentage, sulfate, calcium, magnesium, sodium, potassium, and chlorine percentage were measured using available methods. Independent t-test was used to examine the differences in soil properties between the subsoil and the open space.
Result: In general, the results showed that there was a significant difference between the amount of electrical conductivity, organic matter, calcium, magnesium and chlorine in the subsurface soil of Seidlitzia saline and outdoor soil of Seidlitzia area at 1% level. The amount of magnesium (37.54%), chlorine (18.5 ppm), electrical conductivity (44.55 millisiemens/meter), organic matter (0.62%), and calcium (86 ppm) is higher under the canopy of the halophilic plant than in the open air. Sand, clay, cement (generally texture), amount of potassium, sulfate, sodium, the particles larger than 2 mm and the amount of soil nitrogen in the cover and open soil of Seidlitzia had no significant difference. The results also showed that between acidity, organic matter, calcium, there was a significant difference between magnesium and potassium subsurface of camouflage and outdoor soil and between electrical conductivity, there was no significant difference between sand, clay, silt, chlorine, sulfate, sodium, particles larger than 2 mm and the amount of soil nitrogen in the cover and outdoor of the plant. The amount of organic matter (3.52%), potassium (2.16 ppm), calcium (4.24 ppm), and magnesium (5.68 ppm) under almond trees is higher than in the open air, and acidity (1.7) is higher in the open air than under the trees. The difference in calcium between the soil under the almond tree canopy and the open area was estimated to be 0.38 meq/L on average. The difference in magnesium between the soil under the almond tree canopy and the control area was estimated to be 3.52 meq/L on average. The difference in potassium between the soil under the almond tree canopy and the open area was measured to be 0.26 meq/L.
Conclusion: Plants have different effects on soil. These effects can be both positive, improving soil conditions, and negative, causing soil degradation and loss. In general, the two species of A. scoparia and S. rosmarinus do not have a negative and destructive effect on the soil of their habitat and subsoil, and considering the ecological conditions of the habitat and the vegetative conditions of the species in question, these two species can be used to improve and restore rangelands.