Document Type : Research Article
Authors
1 Tarbiat Modares University
2 Islamic Azad University
Abstract
Abstract
Vegetation, as a key factor in ecosystems, has significant impacts on soil properties through multiple ecological processes. Vegetative covers contribute to soil structure and composition by stabilizing organic matter, controlling erosion, regulating moisture, facilitating nutrient cycling, and fostering microbial activity. While extensive research has elucidated the effects of various vegetation types on the physical and chemical properties of soil, the biological attributes of soil under different vegetation covers, particularly tree and shrub species, remain underexplored. This study aims to comprehensively evaluate the characteristics of the organic and mineral soil layers in areas dominated by Quercus macranthera tree cover, Crataegus microphylla shrub cover, Berberis integerrima shrub cover, and a mixed Crataegus microphylla and Berberis integerrima shrub cover in Rudbar County, Guilan Province, Iran. By examining these diverse vegetation types, the study seeks to elucidate their differential impacts on soil health and ecosystem functionality, providing insights for sustainable land management.
Materials and Methods
To investigate the influence of vegetation cover on soil properties, a rigorous site selection process was employed. Following preliminary field assessments, study areas were chosen to ensure continuity of vegetation cover and minimal variations in topographic factors, including elevation above sea level, slope gradient, and aspect. This approach minimized confounding variables, allowing for accurate comparisons across vegetation types. In each habitat, two 100 m × 100 m plots were implemented, with a minimum separation of 500 meters to account for spatial variability. Within each one-hectare plot, five soil samples (30 cm × 30 cm surface area, 10 cm depth) were collected from the organic and mineral layers at the four corners and the center of the plot. In total, 10 litter samples and 10 soil samples were collected from each vegetation type and transported to the laboratory for detailed analysis. Laboratory assays evaluated a suite of physical, chemical, and biological parameters, including soil aggregate stability, nutrient content, enzymatic activities, and microbial community dynamics, to provide a comprehensive understanding of soil responses to vegetation cover.
Results and Discussion
The findings revealed marked differences in soil properties across the studied vegetation types. The Q. macranthera tree cover exhibited the highest amount of essential nutrients in the organic layer, including nitrogen, phosphorus, potassium, calcium, and magnesium, reflecting its capacity to enhance nutrient cycling. In contrast, the B. integerrima shrub cover consistently showed the lowest nutrient amounts, suggesting limited contributions to soil fertility. Analysis of physical and chemical soil properties further underscored these disparities. The Q. macranthera cover demonstrated superior soil aggregate stability, higher clay content, increased coarse and fine aggregate percentages, optimal pH, and elevated levels of total nitrogen, ammonium, nitrate, phosphorus, potassium, calcium, and fine root biomass. Enzymatic activities, including urease, acid phosphatase, arylsulfatase, and invertase, were also significantly higher under Q. macranthera, indicating robust microbial and biochemical processes. Conversely, B. integerrima cover recorded the lowest values for these parameters, highlighting its limited impact on soil structure and function. Particulate and dissolved organic nitrogen levels were similarly highest under Q. macranthera, reinforcing its role in organic matter dynamics. Biological soil properties mirrored these trends. The Q. macranthera cover supported the highest densities of soil microfauna, including Acarina, Collembola, and nematodes, as well as abundant protozoa, fungal, and bacterial populations. Metrics of microbial activity, such as basal respiration, substrate-induced respiration, microbial biomass nitrogen, and microbial biomass phosphorus, were also maximized under this tree cover, reflecting a thriving soil microbial community. In contrast, B. integerrima cover exhibited the lowest values for these biological indicators, suggesting a less supportive environment for soil biota. Temporal analysis of carbon mineralization revealed significant variations at weeks 2, 4, 5, 8, and 12, with no notable changes at weeks 1 and 17. The highest carbon mineralization rates were observed under Q. macranthera, while B. integerrima showed the lowest. Nitrogen mineralization followed a similar pattern, with significant changes on days 7, 14, 21, 28, and 35, and the highest rates under Q. macranthera. These results collectively indicate that vegetation type, combined with topographic factors like elevation, significantly shapes the physical, chemical, and biological characteristics of soil in Rudbar County.
Conclusion
This study demonstrates that Q. macranthera tree cover significantly enhances soil quality compared to C. microphylla, B. integerrima, and their mixed shrub covers. The superior physical, chemical, and biological properties observed under Q. macranthera highlight its critical role in fostering soil microbial communities, improving nutrient cycling, and maintaining soil fertility. Enhanced carbon and nitrogen mineralization rates further underscore the importance of this tree species in driving biogeochemical processes essential for ecosystem health. These findings have important implications for land-use planning, forest management, and ecological restoration in Rudbar County. By prioritizing Q. macranthera in reforestation and conservation strategies, land managers can optimize soil productivity and ecosystem resilience. Future research should focus on long-term monitoring of these soil-vegetation interactions and explore additional environmental factors, such as climate and land-use history, to further refine management practices. The integration of such data will support the development of sustainable strategies that balance ecological health with agricultural and forestry objectives, ensuring the long-term vitality of Rudbar County’s ecosystems.
Keywords
- Soil fertility
- enzymatic activity
- carbon and nitrogen mineralization
- soil physical and chemical properties
Main Subjects
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