Analysis of Vegetation Cover and Species Diversity Changes in Iran's Warm Semi-Steppe Ecosystems (Case Study: Bardemar Region, Khuzestan Province)

Document Type : Research Paper

Authors

1 Assistant Professor, Forests and Rangelands Research Department, Khuzestan Agricultural and Natural Resources Research and Education Center, Agricultural Research Education and Extension Organization, AREEO, Ahvaz, Iran.

2 Assistant Professor, Soil Conservation and Watershed Management Research Department, Lorestan Agricultural and Natural Resources Research and Education Center, Agricultural Research Education and Extension Organization, AREEO, Khorramabad, Iran.

3 Retired Assistant Professor, Forests and Rangelands Research Department, Khuzestan Agricultural and Natural Resources Research and Education Center, Agricultural Research Education and Extension Organization, AREEO, Ahvaz, Iran.

4 Assistant Professor, of Research institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran.

10.29252/aridbiom.2026.3987

Abstract

Rangelands serve as crucial reservoirs of biodiversity and play a vital role in the balance of dry and semi-arid ecosystems. This research aimed to analyze the trends in vegetation cover and species diversity in the semi-arid warm rangelands of the Bardemar region in Khuzestan province, and to investigate their relationship with rainfall fluctuations over a seven-year period (2018-2024). Field sampling was conducted using a random-systematic method, employing four fixed transects and 40 one-square-meter plots in each sampling period. Throughout this duration, parameters including canopy cover percentage, density, and above-ground plant biomass were measured, and species diversity indices, namely the Simpson and Shannon-Wiener indices, were calculated. The studied area's flora consists of 113 species from 31 plant families, with Asteraceae (28 species), Apiaceae (8 species), and Lamiaceae (3 species) being the richest families. Annual plants (therophytes), represented by 72 species (64%), constitute the dominant life form, followed by hemicryptophytes (19%) and chamaephytes (8%). The obtained results revealed significant fluctuations in vegetation parameters. Canopy cover percentage increased from 18.80% in 2018 to 37.10% in 2023, while forage production varied between 140.59 and 400.49 kg of dry matter per hectare. Data indicated that the peak in both the quantity and quality of vegetation occurred during the high-rainfall years of 2019 and 2023, which received 312.75 mm and 320.65 mm of precipitation, respectively. Consistent with these observations, the Shannon index value increased from 0.76 in 2018 to 1.05 in 2021, and the Simpson index also recorded higher values (0.57 to 0.60) during wetter years, indicating a positive influence of rainfall on species richness and evenness. In conclusion, the findings of this study clearly demonstrate the strong dependence of the structure and function of vegetation in semi-arid warm rangelands on rainfall fluctuations. It emphasizes that annual precipitation acts as the primary environmental factor controlling the dynamics and diversity of these sensitive ecosystems.

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References

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Journal of Arid Biome
Volume 15, Issue 1
March 2025
Pages 65-83

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