Stable Isotope Geochemistry of Carbonates and Organic Carbon in Selected Soils from Chaharmahal Bakhtiari Province, Iran

• Published in: Communications in soil science and plant analysis 2004-12, Vol.35 (11-12), p.1681-1697
• Main Authors: Salehi, M. H., Khademi, H., Eghbal, M. K., Mermut, A. R.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; Iranian soils; Organic matter; Pedogenic carbonates; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plants; Soil genesis; Soil science; Soil surveys, classification and mapping, soil genesis; Stable isotopes
• ISSN: 0010-3624; 1532-2416
• DOI: 10.1081/CSS-120038562

Stable isotope ratios of soil carbonates are useful indicators to establish ecological and environmental changes. The objective of this study was to provide information about the environmental conditions for the formation of calcic horizon in Shahrekord area, in the central west of Iran. The soil moisture and temperature regimes in the study area are xeric and mesic, respectively. The δ 13 C and δ 18 O values of pedogenic carbonates and bulk soils were measured in 17 calcic horizons of selected soils derived from calcareous alluvium. In addition, the δ 13 C and δ 18 O values of three parent rock samples and the δ 13 C value of soil organic matter in selected pedons and eight native plants in the region were determined. Results suggest that pedogenic carbonates range from 52 to 96% of total carbonates. Stable isotopic composition of carbonatic pendants shows that the older layers are more depleted in 13 C in comparison with younger precipitates. This is likely due to the fact that the older parts precipitated under somewhat different ecological conditions than those of younger parts. Isotopic composition of organic carbon shows that current vegetation consists of C 3 plants; whereas, the pedogenic carbonate in the soils was formed in conditions with a lower proportion of C 3 plant species. This can be attributed to human induced land degradation and inappropriate land management in the area, which caused rapid changes in the community of plant species. The results show that the stable isotope composition of carbon can be a good indicator for assessing the degree of land degradation.