University of Zabol
Abstract: (662 Views)
Background and objectives: Rangeland ecosystems are one of the most extensive terrestrial ecosystems that cover approximately half of the Earth's land surface. they have an essential role in ecological sustainability, biomass production, and the regulation of water and nutrient cycles. The amount of soil organic carbon and nitrogen storage is the key indicator in assessing the health of these ecosystems. These issues have particular importance in arid and semi-arid regions, due to the high sensitivity of these regions to environmental stresses and the fragmentation of soil structure.
Rangeland management can improve soil conditions and increase nutrient storage, including carbon and nitrogen, by impacting biological and chemical processes in the soil through strategies such as enclosure. The present study was designed and implemented to investigate the effect of enclosure on total soil organic carbon and nitrogen storage, as well as changes in plant species diversity and vegetation cover, in arid and semi-arid rangelands of the Sarbisheh Plain, located in South Khorasan Province.
Methodology: To evaluate the effect of enclosure management on soil properties and vegetation cover, two sites with similar physiographic, climatic, and topographic conditions were selected. One of the sites was managed under an enclosure regime, while the other was subjected to free grazing. Soil sampling was conducted in May 2021 using a systematic-random method. At each site, six 100-meter transects were established—three parallel and three perpendiculars to the natural slope of the land—with approximately 50 meters spacing between them. Along each transect, ten 1×1 m quadrats were laid out at 10-meter intervals to record vegetation parameters. Soil samples were collected from three depths (0–15, 15–30, and 30–45 cm) after removing the surface litter by digging soil profiles at the beginning, middle, and end of each transect. Samples from the same depth within each transect were composited to create a representative sample for that depth. The composite samples were then transported to the laboratory for analysis of soil organic carbon and total nitrogen concentrations. Laboratory data were statistically analyzed using a completely randomized design (CRD) through SPSS Statistics software version 26. To compare the means between treatments, one-way analysis of variance (One-Way ANOVA) and independent t-tests were employed.
Results: The results showed that the diversity and percentage of canopy cover were significantly higher in the enclosed area compared to the grazed area (23.5% vs. 11.2%). The dominant species in both sites were perennial shrubs from the Papilionaceae, Compositae, and Chenopodiaceae families.
Analysis of variance showed that soil depth significantly affected all measured soil parameters, including organic carbon percentage, total nitrogen, bulk density, carbon stock, and nitrogen stock (p < 0.01). The highest concentrations of organic carbon (2.12 mg/kg) and total nitrogen (0.8 mg/kg) were observed in the surface layer (0–15 cm). In contrast, bulk density increased with depth and reached 1.29 g/cm³ at the 30–45 cm layer. Despite lower nutrient concentrations in deeper layers, the highest carbon stock (7.79 t/ha) was found at a depth of 30–45 cm, likely due to increased soil density. A comparison between the two sites showed that carbon stock was significantly higher in the enclosed area than in the grazed area (6.53 vs. 3.07 t/ha). Although total nitrogen stock did not differ significantly overall, both carbon and nitrogen stocks were significantly higher in the enclosed area at the intermediate depth (15–30 cm).
Conclusion:The findings of this study indicate that enclosure, as an effective rangeland management strategy, can boost biodiversity and improve soil quality by decreasing grazing pressure. Given the vital role of soil carbon and nitrogen storage in arid and semi-arid ecosystems, enclosures can play a significant part in enhancing ecosystem function and helping to reduce the impacts of climate change. Therefore, periodic enclosure practices are recommended in rangeland management programs, especially in sensitive and degraded rangelands. Furthermore, integrating this approach with complementary restoration techniques, such as native species
cultivation and improvement of soil physical properties, may further enhance ecological resilience and the sustainable use of rangeland ecosystems.
Rangeland management can improve soil conditions and increase nutrient storage, including carbon and nitrogen, by impacting biological and chemical processes in the soil through strategies such as enclosure. The present study was designed and implemented to investigate the effect of enclosure on total soil organic carbon and nitrogen storage, as well as changes in plant species diversity and vegetation cover, in arid and semi-arid rangelands of the Sarbisheh Plain, located in South Khorasan Province.
Methodology: To evaluate the effect of enclosure management on soil properties and vegetation cover, two sites with similar physiographic, climatic, and topographic conditions were selected. One of the sites was managed under an enclosure regime, while the other was subjected to free grazing. Soil sampling was conducted in May 2021 using a systematic-random method. At each site, six 100-meter transects were established—three parallel and three perpendiculars to the natural slope of the land—with approximately 50 meters spacing between them. Along each transect, ten 1×1 m quadrats were laid out at 10-meter intervals to record vegetation parameters. Soil samples were collected from three depths (0–15, 15–30, and 30–45 cm) after removing the surface litter by digging soil profiles at the beginning, middle, and end of each transect. Samples from the same depth within each transect were composited to create a representative sample for that depth. The composite samples were then transported to the laboratory for analysis of soil organic carbon and total nitrogen concentrations. Laboratory data were statistically analyzed using a completely randomized design (CRD) through SPSS Statistics software version 26. To compare the means between treatments, one-way analysis of variance (One-Way ANOVA) and independent t-tests were employed.
Results: The results showed that the diversity and percentage of canopy cover were significantly higher in the enclosed area compared to the grazed area (23.5% vs. 11.2%). The dominant species in both sites were perennial shrubs from the Papilionaceae, Compositae, and Chenopodiaceae families.
Analysis of variance showed that soil depth significantly affected all measured soil parameters, including organic carbon percentage, total nitrogen, bulk density, carbon stock, and nitrogen stock (p < 0.01). The highest concentrations of organic carbon (2.12 mg/kg) and total nitrogen (0.8 mg/kg) were observed in the surface layer (0–15 cm). In contrast, bulk density increased with depth and reached 1.29 g/cm³ at the 30–45 cm layer. Despite lower nutrient concentrations in deeper layers, the highest carbon stock (7.79 t/ha) was found at a depth of 30–45 cm, likely due to increased soil density. A comparison between the two sites showed that carbon stock was significantly higher in the enclosed area than in the grazed area (6.53 vs. 3.07 t/ha). Although total nitrogen stock did not differ significantly overall, both carbon and nitrogen stocks were significantly higher in the enclosed area at the intermediate depth (15–30 cm).
Conclusion:The findings of this study indicate that enclosure, as an effective rangeland management strategy, can boost biodiversity and improve soil quality by decreasing grazing pressure. Given the vital role of soil carbon and nitrogen storage in arid and semi-arid ecosystems, enclosures can play a significant part in enhancing ecosystem function and helping to reduce the impacts of climate change. Therefore, periodic enclosure practices are recommended in rangeland management programs, especially in sensitive and degraded rangelands. Furthermore, integrating this approach with complementary restoration techniques, such as native species
cultivation and improvement of soil physical properties, may further enhance ecological resilience and the sustainable use of rangeland ecosystems.
Keywords: Enclosure management, Rangeland ecosystems, Carbon sequestration, Soil quality, Soil organic carbon
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