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Department of Rehabilitation of Arid and Mountainous Regions, Faculty of Natural resources, University of Tehran, Karaj, Iran , hjoneidi@ut.ac.ir
Abstract: (315 Views)
1- Introduction:
The rising concentration of greenhouse gases, particularly carbon dioxide (CO₂), has emerged as one of the most pressing environmental challenges of the 21st century. Carbon sequestration within natural ecosystems, including rangelands, is recognized as an effective strategy for mitigating greenhouse gas emissions and combating climate change. Due to their vast expanse and substantial capacity for carbon storage in both biomass and soil, rangelands play a pivotal role in the global carbon cycle. The potential for carbon storage in rangelands is influenced by various factors, including plant species composition, geographical location, and management practices. This study hypothesizes that Artemisia-dominated rangelands exhibit a high capacity for carbon sequestration due to their extensive and persistent coverage. Moreover, key environmental variables—such as soil characteristics, vegetation dynamics, and topography—alongside management practices—including grazing intensity, conservation measures, and land-use interventions—are expected to significantly impact the carbon sequestration potential of these ecosystems. Given the importance of understanding these dynamics, this study aims to evaluate the carbon storage capacity of Artemisia rangelands in Semnan Province while identifying the ecological and management factors that influence this process.
2-Methodology
The study areas in Semnan province, including the counties of Ivanaki, Damghan, and Semnan, with the highest percentage of Artemisia sieberi presence, were selected. Human-managed treatments included grazing, corrective measures such as the construction of furrows and flood spreading, land-use changes from rangeland to salt cedar plantation, and the cultivation of fruit trees (pistachio). Environmental treatments considered were topographic features (slope, aspect, and elevation), vegetation characteristics (density, canopy cover, and biomass), and climate (temperature and precipitation) at the study sites. Vegetation sampling was performed using a systematic random method. In each plot, canopy cover, density, plant size, litter, and the biomass of both aboveground and underground parts were determined. Soil samples were collected at three different depths (0-20 cm, 20-40 cm, and 40-60 cm, and 75-100 cm) corresponding to the maximum rooting depth. Data analysis to assess the effect of ecological and management factors on the organic carbon storage in the study treatments was performed using ANOVA to compare the mean values of measured parameters in soil, litter, and biomass.To assess the effect of human factors on the carbon storage in the ecosystem, independent t-tests were applied for study and control areas, while Principal Component Analysis (PCA) was used to identify the most influential ecological factors on carbon sequestration per unit area.
3- Results
The results revealed that the total organic carbon reserves in the Artemisia rangelands of Semnan province (including soil, biomass, and litter) averaged 25.5 tons per hectare, with minimum and maximum values of 10 and 55 tons per hectare, respectively, and were significantly influenced by environmental and management factors. The effect of grazing on carbon sequestration depended on the grazing intensity, with higher grazing intensity leading to a reduction in the ecosystem's carbon storage capacity. Land-use change from Artemisia rangeland to black salt cedar plantation significantly increased carbon reserves, whereas the conversion of rangeland to pistachio cultivation did not have a meaningful effect on carbon sequestration capacity. Corrective measures had varied effects on water retention in different regions, depending on the type and extent of their implementation, with proper project location being a key factor in their success.
Environmental factors also played a significant role in the amount of organic carbon storage in Artemisia rangelands. Factors such as soil properties (clay content, nitrogen, and lime) and topography (elevation) had a considerable impact on carbon reserves.
PCA analysis of environmental variables (topography, soil, and climate) in Artemisia rangelands indicated that the first, second, and third principal components (elevation, nitrogen content, and clay content) explained 57.3%, 20.68%, and 9.16% of the variance in carbon sequestration, respectively, with these three components collectively accounting for 87.14% of the total variation in carbon sequestration.
In general, soil accounted for the largest share (87%) of the total carbon reserves in the ecosystem. The contribution of biomass and litter to the total carbon storage per unit area was 12.9% and 0.1%, respectively.
4- Discussion & Conclusions
The present study demonstrated that the average carbon sequestration in Artemisia rangelands in Semnan province is highly influenced by both environmental and management factors. Increasing accessible nitrogen through soil fertility improvement and stimulating plant growth plays a significant role in enhancing carbon sequestration. Moreover, elevation, by affecting the local climate, increased biomass production and canopy cover, improving carbon sequestration capacity.
This study found that soils with higher levels of lime and clay have a greater potential for stabilizing organic carbon. Lime improves soil structure, and clay forms clay-humus complexes, enhancing carbon stability. Grazing intensity played a critical role in altering carbon reserves; intensive grazing led to a reduction in biomass and a decrease in stored carbon.
Additionally, management practices such as appropriate tree planting and furrow construction, if correctly located, had a positive impact on carbon sequestration. The results emphasized that soil, contributing 87%, is the primary carbon reservoir in these ecosystems, with underground biomass holding more than half of the total carbon in the biomass.
Overall, this study highlights the importance of proper grazing management, protection of clay- and lime-rich soils, and the development of suitable corrective projects to increase carbon sequestration capacity in Artemisia rangelands, recognizing these ecosystems as effective biomes for mitigating climate change.
Type of Study: Research |
Received: 2025/04/30
Received: 2025/04/30
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