The Effect of Long-term Enclosure on the Amount of Soil Carbon Storage in Subtropical Wooded Rangelands of Khuzestan Province
Subject Areas : Optimal management of water and soil resourcesMahdi Abbasi 1 , Behnaz Attaeian 2 * , Mina Rabie 3 , Ali Rostami Khanizadeh 4
1 - 1) Graduate Msc., Department of Natural Engineering, Faculty of Nature Resources and Environment, Malayer University, Malayer, Iran.
2 - Assistant Professor, Department of Nature Engineering, Faculty of Natural Resources and Environment, Malayer University, Malayer, Iran.
3 - Associate Professor, Department of Natural Resources and Environment, Payamnoor University, Tehran, Iran.
4 - Msc., Lorestan Environment Office, KhoramAbad, Iran
Keywords: Carbon sequestration, Kharkhe national park, Rangeland management,
Abstract :
Background and Aim: Rangelands serve as a storage for more than one-third of the Earth’s carbon stocks, absorbing atmospheric carbon dioxide through vegetation and store it in plant tissues and subsequently in the soil. Changes in the quantity and quality of organic matter can be influenced by litter, canopy cover, underground biomass, and soil composition. Generally, the inconsistency of grazing effects on the carbon sequestration potential in rangeland ecosystems across different regions highlights the need for study and examination of grazing management practices in various areas. Considering that most of Kurdistan province lies within the semi-steppe region and livestock grazing is regarded as the primary land use in these rangelands, this research investigates the effect of long-term enclosed of semi-steppe wooded grasslands on soil organic carbon storage in Karkheh National Park, Khuzestan Province.
Methods: To select the sampling locations, there were no restrictions in terms of topographic conditions. Therefore, four 100-meter transects were randomly In completely random design and 14 soil samples were collected along each transect at two depths of 0 to 10 cm and 10 to 30 cm, based on previous studies and the determination of the boundary distinguishing the surface and subsurface soil horizons. To compare the amount of carbon storage, an equal number of samples were also collected from an grazed area. Subsequently, the physical and chemical properties of the soil, including the carbon, nitrogen, texture, bulk density, electrical conductivity (EC), and acidity (pH) were measured. The soil samples were air-dried, and after crushing the aggregates, separating roots, stones, and other impurities, they were ground and passed through a 2 mm sieve (mesh 20). The Walkley-Black method was used to measure soil organic carbon, and the aggregate method was used to calculate bulk density. After collecting the data, SPSS v.18 was used to do independent t-test comparing the average values. Significance levels of 0.05 and 0.01 were considered. Prior to statistical analysis, the necessary assumptions regarding normality and homogeneity of variances were checked.
Results: The results showed the analysis of the physical and chemical properties of the soil at two depths of 0 to 10 cm (surface) and 10 to 30 cm (subsurface) in enclosed and grazing areas indicated that enclosed and grazed treatments significantly affected soil carbon storage at the surface depth (0-10 cm), the amount of soil nitrogen (0-10 cm), and the bulk density showing an increasing effect associated with depth. It appears that the soil in both areas have high organic matter and nitrogen content due to the aboveground and underground plant biomass. However, no significant change was observed on soil acidity between both the enclosed and grazed areas, which could be due to the same soil parent materials in both study sites. Additionally, grazing, in contrast to enclosed, had a significant and decreasing effect on electrical conductivity (EC) at the depth of 0-10 cm. A significant effect was also observed in the C/N ratio in the soil of the enclosed area compared to the grazing area at the depth of 0-10 cm. The findings indicated that in the study area, protection led to a significant increase in the amount of soil carbon storage at the surface depth (0-10 cm), the amount of soil nitrogen (0-10 cm), soil acidity (0-10 cm), and electrical conductivity (EC) (0-10 cm). Furthermore, the grazing had a significant increasing effect on the bulk density (0-10 cm). Nevertheless, neither encosion nor grazing had a significant effect on the C/N ratio in the soil of the study area.
Conclusion: Overall, the results of the present study indicate that the soil of enclosed area has more suitable conditions for increasing soil carbon sequestration compared to the soil of grazed areas in terms of physical and chemical properties. Excessive exploitation in grazing ecosystems has led to a reduction in carbon storage and sequestration in rangelands. Therefore, implementing common remediation and management programs, such as exclusion, seems essential for enhancing carbon sequestration and forage production in various rangeland ecosystems.
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