The effect of long-term intensive grazing on soil properties and the reversibility of dominant species in Ghoshchi rangelands of Urmia

Background and purpose: Rangeland ecosystems are of great importance due to the diversity of products and services they provide, including livestock production, wildlife refuges, Rangeland ecosystems are of great importance due to the diversity of products and services they provide, including livestock production, wildlife refuges, Rangeland ecosystems are of great importance due to the diversity of products and services they provide, including livestock production, wildlife refuges, plant and animal species diversity, and the regulation of runoff flow and quality. These ecosystems are sensitive to changes in environmental factors (1). Long-term rangeland assessment provides the basis for systematic planning, prevention of rangeland degradation, and soil conservation. It is also possible for any plant to spread within specific geographical areas, because plants have specific environmental needs that must be met if they are to grow and reproduce in a given area. Reversibility assessment of plant species after overgrazing provides important information about the capacity of pastures to restore their structure and function plus prevent soil erosion. In this study, 4-year research was conducted in the Urmia Ghoshchi rangelands for investigating the effect of graze conditions on the physical, chemical and soil erosion and the reversibility of the dominant plant species after overgrazing.
Materials and methods: A 2-hectare site in Urmia Ghoshchi region was divided into two 1-hectare sites under graze and exclosure using intermediate fencing and was investigated for 4 years from 1400 to 1403. In the graze site, overgrazing by deliberate animal husbandry for 2 weeks at the beginning of the spring of 1400 and the reversibility of the dominant plant species grazed in the spring and summer of each year from the spring of 1400 to the spring of 1403 and a total of 7 times by transect quadrat technic and plotting was determined at the same points as before graze. On the other hand, the intensity of soil erosion in both sites under exclosure and under overgraze was evaluated with the four criteria of surface erosion, furrow, watercourse and ditch. Soil sampling was done at two depths of 0 to 10 and 10 to 20 cm inside each plot. Surface erosion was determined by MWD and organic matter (OM), furrow erosion by field observation and ditch erosion using EC and sodium absorption ratio (SAR). Surface erosion was expressed as an index of the ratio of soil particle diameters at a given frequency in the topsoil (0-10 cm) to the subsurface soil (10-20 cm). In terms of soil susceptibility to erosion, acidity of 5.9 and electrical conductivity of 0.1 are the thresholds for linear erosion, including tubular, furrow, and ditch erosion. On the other hand, the amount of clay in the soil texture of the area is below 10 percent, the soil is coarse-textured, and the pores of the soil are preserved, and water penetration into the soil will not decrease over time, leading to the creation of surface runoff. As a result, the runoff will not deepen its bed, which will increase and cause ditch erosion.
Findings: The results showed that the effect of year is significant only on OM and soil pH. Also, the effect of graze conditions was significant on all parameters except OM, and the interaction effect of year on graze conditions was not significant on any of the parameters. The highest amount of OM was obtained in 1401 at the rate of 1.55 and the lowest in 1402 at the rate of 1.1. The highest amount of pH was obtained in 1403 at the rate of 7.83 and the lowest in 1402 at the rate of 7.59. pH, EC and SAR in the site under grazing were significantly higher than the site under exclosure, but the soil MWD in the site under exclosure was significantly higher than the site under graze. The results of the reversibility section in the site under overgraze showed that the effect of year, season and their interaction on the reversibility of Artemisia Sieberi are significant. The lowest amount of reversibility was 6% in the spring of 1400 and the highest was 124.3% in the summer of 1403. Among the parameters under investigation, there was almost a direct relationship between OM and reversibility, but the rest of the soil properties had no special relationship with reversibility. The soil of the area was in the sodic layer, and regardless of ditch erosion, which was very low in both sites, the other types of erosion were higher in the graze site than in the exclosure site. In total, overgraze, in addition to the negative effects it had on the vegetation, also caused more soil erosion.
Conclusion: pH, EC and SAR in the site under graze were significantly higher than the site under flooding, but the average weight diameter of soil grains in the site under flooding was significantly higher than the site under graze. The results of the reversibility section showed that the effect of year, season and interaction effect of them on the reversibility of the Artemisia Sieberi are significant. Lowest value of reversibility was 6% in the spring of 1400 and the highest value was 124.3% in the summer of 1403. It is suggested that in practice, pastures should be utilized to the extent of their capacity. The grazing season and livestock entry into the field should be done in an expert manner. The practical conclusion is that after heavy grazing, the pasture should be given a chance to recover so that the dominant plant species can return to the field and soil erosion can be prevented.