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Department of Nature Engineering and Medicinal Plants, Faculty of Agriculture, University of Torbat Heydarieh, Torbat Heydarieh , Iran , me.bashiri@yahoo.com
Abstract: (7 Views)
1- Introduction
The most important factors affecting the water infiltration rate on the rangeland surface are livestock trampling and reduced vegetation cover due to excessive grazing. Providing any solution for managing rangeland improvement requires understanding the effect of grazing and enclosure on vegetation cover changes and their relationship with soil parameters, including permeability. Today, the rate of exploitation of the country's rangelands is much higher than the permissible limit, and the major part of this exploitation is dedicated to livestock. Premature and excessive grazing of rangelands by livestock affects the quantity and quality of vegetation cover, permeability, porosity, soil moisture, runoff, and erosion rate of rangeland soil through compaction and physical destruction of the soil. In this regard, the present study was conducted to investigate the effect of micro-terraces created in livestock traffic routes on runoff, sediment, and permeability in six regions of the rangelands in the Torbat-Heydarieh Senobar watershed within 36 points (18 micro-traces and 18 controls) and using a portable rainfall simulator and double rings.
2- Materials & Methods
The rainfall intensity for this study was determined using the Intensity-Duration-Frequency (IDF) curves specific to the region, derived from data collected at the Torbat-Heydariyeh meteorological station near the research area. The intensity was based on runoff observations from preliminary tests, indicating a rainfall rate of 0.9 mm/min, corresponding to a return period of 10 years. During the study, the erosion plots were subjected to simulated rainfall for 15 minutes.
Soil erosion was quantified using an Eijkelkamp rain simulator with a plot area of 30 × 30 cm. During precipitation simulation, runoff volume was determined via direct volumetric measurement using a graduated cylinder. The resulting sediment yield was transported to the laboratory, filtered through Whatman 42 filter paper, and subsequently oven-dried at 110°C for 24 hours before gravimetric analysis. Additionally, soil permeability was assessed at each sampling point using a double-ring infiltrometer. Following data collection, statistical analyses were performed using SPSS v.27, including one-way ANOVA and independent samples t-test to evaluate significant differences between experimental conditions.
3- Results
All selected points for field operations were located in rangelands characterized by hillslopes, specifically within the marl and sandstone geological units. Physiographic factors, such as direction, elevation, and slope, were also carefully chosen to minimize the impact of environmental variability. The normal distribution of data across different groups indicates that environmental changes in the field were not significant. As a result, no interference from external factors was observed, and there was no need for more repetitions in the field experiments.
The results of field data analysis showed a significant difference (P. Value=0.05) in infiltration variables in all six regions and runoff in five regions between the treatment and the control. However, in the sediment load and concentration variables, the treatment was significantly higher than the control at only one point. There was a significant difference (P. Value=0.05) between the six study areas only in the sediment load variable, and considering all six regions together, a significant difference (P. Value=0.01) was observed between the values obtained from the treatment and control groups in all four research variables.
4- Discussion & Conclusions
The analysis of the homogeneous units showed that, with the exception of the sediment load variable and one area affected by lighter soil texture, the six study areas did not exhibit significant differences. However, the four variables -infiltration, sediment load, sediment concentration, and runoff-measured in micro-terraces due to continuous livestock traffic displayed significantly different values compared to the control points. As a result, given the widespread presence of micro-traces caused by livestock trampling in the country's rangelands and its significant effect on runoff, sediment, and soil infiltration processes, it is necessary to plan in some way in the development and implementation of a rangeland grazing management program to stop the development of soil degradation process and give the rangeland soil a proper recovery opportunity. Due to the excessive grazing in the country's rangelands and the pressure on the soil, a fundamental revision of livestock grazing permits and rangeland management plans is necessary. Finally, considering the limitations of the research, it is recommended that the temporal changes in runoff and sediment during the simulation and higher rainfall intensities with different carrying capacities and in heavy soils be examined to summarize the findings.
Received: 2025/02/14
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