نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه مهندسی طبیعت، دانشکده منابع طبیعی و محیط زیست، دانشگاه ملایر، ملایر، ایران.
2 استادیار گروه مرتع و آبخیزداری، دانشکده منابع طبیعی، دانشگاه ملایر، ملایر، ایران
3 گروه احیاء مناطق خشک و کوهستانی دانشگاه تهران، تهران، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Carbon sequestration is one of the ways to reduce the amount of carbon dioxide in the atmosphere and thereby reduce the negative consequences of climate change. In this research, the initial evaluation of the amount of carbon reserves in Halocnemum strobilaceum habitat in Mighan Arak desert and determining the validity of Rothamsted Carbon Model (RothC) as well as investigating future two climate scenarios (Absence and onset of climate change) in estimating the changes in soil organic carbon stock were done. Sampling was done in the form of random-systematic design using 48 points in the topsoil. To evaluate the efficiency of the model, the coefficient of explanation (R2), correlation coefficient (r), root mean square error (RMSE) and also the efficiency index of the model implementation (PE) were used. The results showed that the highest and lowest amount of soil organic carbon in the habitats of this plant for each of the above scenarios, respectively, with the values of 19/1687, 20/0824, 20/0802 corresponding to the habitat of this plant in the west of Miqan desert and 9/7525, 10/2211, 10/22 tons per hectare in the south of Meyqan desert. Also, the results showed the reduction of all active carbon reserves, such as the reservoirs of degradable plant material, resistant plant material, microbial biomass, and soil humus organic matter equivalent to 14/167, 16/421, 13/976 and 1/91% respectively. It will decrease compared to the conditions of non-occurrence of climate change. Considering the fragile state of the Miqan desert ecosystem and other playas of Iran, if the economic value (the economic value of each ton of carbon is at least 50 US dollars) and the environmental value of carbon deposition (reducing the effects of global warming, etc.) add to the sum of the benefits and services of these ecosystems is done, the need to protect these ecosystems becomes more obvious.
کلیدواژهها [English]
EXTENDED ABSTRACT
Introduction
Atmospheric CO₂ mitigation through soil carbon sequestration is an essential strategy for combating climate change, particularly in arid and semi‑arid ecosystems where organic inputs are limited. Halocnemum strobilaceum, a salt‑tolerant halophyte dominating the edges of the Mighan Desert playa (Arak, Iran), may contribute substantially to below‑ground carbon storage under saline, water‑scarce conditions. This study provides a preliminary quantification of soil organic carbon (SOC) beneath H. strobilaceum, evaluates the Rothamsted Carbon Model (RothC‑26.3) for this environment, and projects SOC dynamics under two contrasting climate scenarios through 2050. By validating RothC in this context, we aim to establish a robust framework for long‑term desert ecosystem carbon monitoring.
Materials and Methods
Field sampling was carried out in summer 2023 using a random‑systematic design across four distinct H. strobilaceum stands (north, south, east, west) on the Mighan playa. At each of 48 sampling points, topsoil (0–25 cm) cores were collected, bulk density recorded in situ, and samples analyzed for texture (hydrometer), pH and electrical conductivity (1:2.5 soil:water), and organic C via Walkley–Black titration. SOC stocks (t ha⁻¹) were computed from percent C, bulk density, and sampling depth.
The RothC‑26.3 model was forced with monthly climate inputs (2005–2022: mean temperature, precipitation, potential evapotranspiration) and estimated plant‑residue inputs based on local biomass data. Two future scenarios were defined for 2023–2050:
No‑change: continuation of long‑term mean climate.
Climate‑change: –10.4 % precipitation and +17.7 % temperature relative to baseline (per Koocheki et al., 2007 projections).
Model calibration in inverse mode employed December 2012 SOC observations (n = 24). Performance metrics included coefficient of determination (R²), Pearson’s correlation (r), root‑mean‑square error (RMSE), and model efficiency index (PE). Measured versus simulated SOC time series were compared using Excel and SPSS v21.0.
RothC exhibited excellent agreement with field observations: R² = 0.99, r = 0.98, RMSE = 0.32 t ha⁻¹, PE = 0.99, indicating negligible bias and high predictive reliability. Baseline (Dec 2023) SOC stocks ranged from 9.8 t ha⁻¹ in the south stand to 20.1 t ha⁻¹ in the west. Under the no‑change scenario, SOC increased modestly by 1.8–2.3 % across all sites by 2050, reflecting steady carbon inputs. Conversely, the climate‑change scenario projected SOC declines of 4.6–5.6 %, with the greatest loss in the northern stand (–5.6 %) and the smallest in the eastern stand (–4.6 %) by Dec 2050. Model outputs also forecast a 7–9 % increase in cumulative soil CO₂ efflux under warming and drying, amplifying carbon losses. These divergent trajectories underscore the sensitivity of desert SOC pools to altered precipitation and temperature regimes.
Our findings demonstrate that the RothC‑26.3 model is robust for simulating SOC in saline, semi‑arid soils and can reliably predict future carbon dynamics under climate change. Projected warming and reduced rainfall may drive a 4–6 % SOC loss and elevated CO₂ emissions by mid‑century beneath H. strobilaceum. To safeguard this ecosystem service, adaptive management—such as controlled grazing, maintenance of shallow water tables, and halophyte stand conservation—is recommended. Future work should involve the establishment of long‑term monitoring stations and experimental plots to refine residue input estimates, validate model projections, and assess the efficacy of management interventions in stabilizing desert SOC stocks.
Conceptualization, Behnaz Attaeian; Methodology, Behnaz Attaeian and Maliha Akbari Bezcheloi, Bijan Azad; Software and modeling, Bijan Azad, Maliha Akbari Bezcheloi; Validation, Behnaz Attaeian, Bijan Azad; Formal analysis, Maliha Akbari Bezcheloi and Bijan Azad; Investigation, Maliha Akbari Bezcheloi; Data curation, Maliha Akbari Bezcheloi; Writing—original draft preparation, Maliha Akbari Bezcheloi; Writing—review and editing, Behnaz Attaeian; Supervision, Behnaz Attaeian; Project administration, Behnaz Attaeian. All authors have read and agreed to the published version of the manuscript.
The raw data generated and analyzed during this study are available from the corresponding author, Behnaz Attaeian, upon reasonable request and pending permission from the co‑authors.
The authors gratefully acknowledge the support of Malayer University, which provided facilities and guidance essential for Maliha Akbari Bezcheloi’s master’s research project.
Not applicable in the study.
The authors declare no conflict of interest.
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