Volume 19, Issue 3 (9-2025)
مرتع 2025, 19(3): 263-282 |
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Ghorbani Z, Jafarian Z, Ghorbani J. Predicting and optimizing the reversibility of plant species after intensive grazing using response surface methodology (RSM) (Case study: rangelands of Ghoshchi region of Urmia). مرتع 2025; 19 (3) :263-282
URL: http://rangelandsrm.ir/article-1-1289-en.html
URL: http://rangelandsrm.ir/article-1-1289-en.html
Department of Range Management, Faculty of Natural Resources, Sari Agricultural Sciences and Natural Resources University, Sari
Abstract: (381 Views)
Introduction and Objective: Evaluating the reversibility of plant populations following livestock grazing and stress periods provides critical insights into the capacity of rangelands to restore their structure and function. In this study, a four-year investigation was conducted in the rangelands of the Ghoshchi region, Urmia, to predict and optimize the reversibility of dominant plant species in different palatability classes after intensive grazing, using the Response Surface Method (RSM).
Methodology: A 2-hectare site in the Ghoshchi area was divided into two 1-hectare plots -one grazed and one ungrazed (exclosure)- separated by intermediate fencing. The experiment was carried out over four years (2021–2024; corresponding to 1400–1403 in the Iranian calendar). In the grazed plot, intensive grazing was applied by deliberately introducing 80 sheep for two weeks at the beginning of spring 1400. The reversibility of dominant species in palatability classes I, II, and III -Kochia prostrata, Artemisia sieberi, and Stipa barbata, respectively- was monitored in spring and summer each year from 1400 to 1403, totaling eight sampling events. Data were collected using the quadrat-transect method at fixed points, and comparisons were made with the exclosure plot. The effects of species, year, and season on reversibility were analyzed. Linear regression models and RSM were developed, and their predictive accuracy was compared using the coefficient of determination (R²). Optimization was also performed within the RSM framework.
Results: The effects of species, year, season, and their two- and three-way interactions on reversibility were statistically significant. The lowest and highest reversibility values were observed as follows: Kochia prostrata: 3.67% (spring 2021) and 105% (summer 1403); Artemisia sieberi: 6% (spring 2021) and 124.33% (summer 2024); Stipa barbata: 9% (spring 2021) and 132.67% (summer 2024). Mean comparisons indicated that among species, Stipa barbata had the highest reversibility; among years, 2024 showed the greatest recovery; and among seasons, summer exhibited the highest reversibility. The linear regression model achieved a coefficient of determination of 0.8486, outperforming RSM (R² = 0.7782). Under the assumption of maximum reversibility, the optimal condition was Stipa barbata in summer 2024, with a reversibility rate of 122.97%. Conversely, under the assumption of minimum reversibility, the optimal condition was Artemisia sieberi in spring 2021, with a reversibility rate of 29.60%.
Conclusion: Species, year, season, and their interactions significantly influenced reversibility. The linear regression model provided more accurate predictions than RSM, which was less reliable when non-quantitative inputs were present. Optimization using RSM identified two ideal scenarios: maximum reversibility with Stipa barbata in summer 2024, and minimum reversibility with Artemisia sieberi in spring 2021. These findings highlight the importance of allowing rangelands sufficient recovery time after heavy grazing so that dominant species, along with others in each palatability class, can reestablish and restore the ecosystem to its natural state and function.
Methodology: A 2-hectare site in the Ghoshchi area was divided into two 1-hectare plots -one grazed and one ungrazed (exclosure)- separated by intermediate fencing. The experiment was carried out over four years (2021–2024; corresponding to 1400–1403 in the Iranian calendar). In the grazed plot, intensive grazing was applied by deliberately introducing 80 sheep for two weeks at the beginning of spring 1400. The reversibility of dominant species in palatability classes I, II, and III -Kochia prostrata, Artemisia sieberi, and Stipa barbata, respectively- was monitored in spring and summer each year from 1400 to 1403, totaling eight sampling events. Data were collected using the quadrat-transect method at fixed points, and comparisons were made with the exclosure plot. The effects of species, year, and season on reversibility were analyzed. Linear regression models and RSM were developed, and their predictive accuracy was compared using the coefficient of determination (R²). Optimization was also performed within the RSM framework.
Results: The effects of species, year, season, and their two- and three-way interactions on reversibility were statistically significant. The lowest and highest reversibility values were observed as follows: Kochia prostrata: 3.67% (spring 2021) and 105% (summer 1403); Artemisia sieberi: 6% (spring 2021) and 124.33% (summer 2024); Stipa barbata: 9% (spring 2021) and 132.67% (summer 2024). Mean comparisons indicated that among species, Stipa barbata had the highest reversibility; among years, 2024 showed the greatest recovery; and among seasons, summer exhibited the highest reversibility. The linear regression model achieved a coefficient of determination of 0.8486, outperforming RSM (R² = 0.7782). Under the assumption of maximum reversibility, the optimal condition was Stipa barbata in summer 2024, with a reversibility rate of 122.97%. Conversely, under the assumption of minimum reversibility, the optimal condition was Artemisia sieberi in spring 2021, with a reversibility rate of 29.60%.
Conclusion: Species, year, season, and their interactions significantly influenced reversibility. The linear regression model provided more accurate predictions than RSM, which was less reliable when non-quantitative inputs were present. Optimization using RSM identified two ideal scenarios: maximum reversibility with Stipa barbata in summer 2024, and minimum reversibility with Artemisia sieberi in spring 2021. These findings highlight the importance of allowing rangelands sufficient recovery time after heavy grazing so that dominant species, along with others in each palatability class, can reestablish and restore the ecosystem to its natural state and function.
Type of Study: Applicable |
Subject:
Special
Received: 2024/10/6 | Accepted: 2025/06/15 | Published: 2025/09/1
Received: 2024/10/6 | Accepted: 2025/06/15 | Published: 2025/09/1
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