Volume 17, Issue 4 (2-2024)
مرتع 2024, 17(4): 602-621 |
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Pournemati A, Sepehry A, Barani H, sefidi K. Quantitative Analysis of Structural Characteristics of Astragalus microcephalus Willd in Different Years After Fire in Semi-Steppe Rangelands of Khalkhal. مرتع 2024; 17 (4) :602-621
URL: http://rangelandsrm.ir/article-1-1214-en.html
URL: http://rangelandsrm.ir/article-1-1214-en.html
Department of Rangeland, Faculty of Rangeland and Watershed Management, Gorgan University of Agricultural Science and Natural Resources, Gorgan
Abstract: (667 Views)
Background and objectives: Rangeland plants undergo continuous changes due to various disturbances, with fire being a significant environmental factor impacting plant communities. In many rangelands, the frequency and extent of fires are increasing, altering the composition and structure of vegetation communities in fire-prone environments. However, limited studies have focused on the effects of fire on the quantitative analysis of shrub plant stands in rangelands, hindering our understanding of fire's impact on structural changes in these plants. This study aimed to analyze the quantitative structural changes of Astragalus microcephalus Willd. over an 8-year period following a fire.
Methodology: One control area and eight fire-affected areas, each covering one hectare and sharing similar environmental conditions and plant communities, were selected. Vegetation sampling was conducted along six 30-meter transects, with 24 points spaced 5 meters apart selected using a systematic-random method. Structural characteristics of the stands were measured by completely harvesting all shrub plant bases using the distance method. Spatial distribution patterns were investigated using Johnson and Zimer's indices, C index, Hopkins, Eberhart, uniform angle, Clark and Evans indices, Mingling index for species admixture, and Berger-Parker index for crown differentiation.
Results: The results revealed a clustered distribution pattern in both the control area and the fire-affected area, as indicated by the Clark-Evans indices and uniformity angle. The C index and Hopkins distribution pattern indicated uniformity, which remained consistent between the control and fire-affected areas, suggesting no alteration in distribution pattern due to fire. The Johnson and Zimer's Index showed varying values for the control and fire-affected areas across different years. The Mingling index indicated weaker mixing in the fire-affected area compared to the control area. The Berger-Parker index indicated increased dominance of Astragalus microcephalus after the fire. Crown differentiation analysis revealed a greater difference in crown size between the control and fire-affected areas in the early years following the fire. One-way analysis of variance showed significant differences between different years after the fire in terms of Clark-Evans, Johnson and Zimer's, and Berger-Parker indices at a confidence level of one percent (p<0.01).
Conclusion: The clustered distribution pattern of Astragalus microcephalus Willd. in Khalkhal rangelands remains unchanged after 8 years following a fire, likely due to factors such as post-fire regrowth from the collar surface, seed distribution type, and reproductive strategy. Fire has led to increased dominance of Astragalus microcephalus and reduced vegetation composition. Understanding changes in structural characteristics of shrub species is crucial for assessing disturbance impacts, studying spatial distribution patterns, species dominance, and dimension differences following disturbances in mountain pastures, and planning for habitat management and restoration.
Methodology: One control area and eight fire-affected areas, each covering one hectare and sharing similar environmental conditions and plant communities, were selected. Vegetation sampling was conducted along six 30-meter transects, with 24 points spaced 5 meters apart selected using a systematic-random method. Structural characteristics of the stands were measured by completely harvesting all shrub plant bases using the distance method. Spatial distribution patterns were investigated using Johnson and Zimer's indices, C index, Hopkins, Eberhart, uniform angle, Clark and Evans indices, Mingling index for species admixture, and Berger-Parker index for crown differentiation.
Results: The results revealed a clustered distribution pattern in both the control area and the fire-affected area, as indicated by the Clark-Evans indices and uniformity angle. The C index and Hopkins distribution pattern indicated uniformity, which remained consistent between the control and fire-affected areas, suggesting no alteration in distribution pattern due to fire. The Johnson and Zimer's Index showed varying values for the control and fire-affected areas across different years. The Mingling index indicated weaker mixing in the fire-affected area compared to the control area. The Berger-Parker index indicated increased dominance of Astragalus microcephalus after the fire. Crown differentiation analysis revealed a greater difference in crown size between the control and fire-affected areas in the early years following the fire. One-way analysis of variance showed significant differences between different years after the fire in terms of Clark-Evans, Johnson and Zimer's, and Berger-Parker indices at a confidence level of one percent (p<0.01).
Conclusion: The clustered distribution pattern of Astragalus microcephalus Willd. in Khalkhal rangelands remains unchanged after 8 years following a fire, likely due to factors such as post-fire regrowth from the collar surface, seed distribution type, and reproductive strategy. Fire has led to increased dominance of Astragalus microcephalus and reduced vegetation composition. Understanding changes in structural characteristics of shrub species is crucial for assessing disturbance impacts, studying spatial distribution patterns, species dominance, and dimension differences following disturbances in mountain pastures, and planning for habitat management and restoration.
Keywords: Distance indices, Distribution pattern, Species mixture, spatial structure, Ecological disturbance, R Software
Type of Study: Research |
Subject:
Special
Received: 2023/08/3 | Accepted: 2024/02/19 | Published: 2024/02/29
Received: 2023/08/3 | Accepted: 2024/02/19 | Published: 2024/02/29
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