Document Type : Research Article

Authors

1 Gorgan University of Agriculture sciences and Natural Resources

2 koeln

3 ferdowsi university of mashhad

4 Isfahan University of Technology

5 Bonn University

Abstract

Introduction: Knowledge about palaeoenviroment and palaeovegetation provides information about how vegetation reacts on climate fluctuations in the past, what will help understanding current and future developments caused by e.g. climate change. Northern Iranian Loess-Plateau forms a strongly dissected landscape with steeply sloping loess hills. This loess record reflects numerous cycles of climate change and landscape evolution for the Middle to Late Quaternary period. therefore, this study was done for reconstruction of palaeoenvironment (climate and vegetation) in loess-palaeosol sequences in northern Iran. Therefore, this study aims at a preliminary reconstruction of palaeovegetation and palaeoenvironment, in loess-palaeosol sequences along a cliomosequnce in Northern Iran.
Materials and Methods: Two loess-palaeosol sequences (Agh Band and Nowdeh sections) were chosen in Golestan province, in northern Iran and step-wise profiles were prepared. Agh Band section is located in the western most part of the Northern Iranian loess plateau and has about 50 m thickness of loess deposits. Nowdeh loess-palaeosol sequence is located about 20 km southeast of Gonbad-e Kavus, in the vicinity of the Nowdeh River. Soil sampling was done in several field campaigns in spring 2012. More than 30cm of the surface deposits were removed in order to reach for undisturbed loess and palaeosols and one mixed sample was taken from each horizonA comparison of palaeosols with modern soils formed under known Holocene climatic conditions, which are derived from substrates with similar granulometric and mineralogical composition are suited for reconstructing past climate and environment. Hence, six modern soil profiles were prepared along the climosequnce and the vegetation cover changed from grassland in the dry area to dense shrub land and forest in the moist part of the ecological gradient. For reconstruction of palaeoenvironment (climate and vegetation) some basic physico-chemical properties, clay mineralogy and n-alkane biomarkers were used.
Results and Discussion: Results of soil texture analysis showed silt particles were dominant (more than 50 %) in the modern soil profiles and loess-paleosol sequences which confirmed aeolian source of loess deposit. Clay content increased while silt content decrease in more strongly developed palaeosol horizons which it may reflected weathering processes of clay and/or its translocation. The modern soil profiles were classified as Entisols, Inceptisols, Mollisols and Alfisols which shows impact of climate as an important soil formation factor in the studied area. Clay mineralogy results in two loess-palaeosol sequences showed that illite, chlorite, kaolinite and smectite are dominant in these deposits. Mineralogical changes in the soil horizons are consistent with morphology and soil evaluation, so smectite, illite-smectite (mixed layer) and vermiculite minerals were dominant minerals in more strongly developed palaeosol horizons indicating to high precipitation and good vegetation cover (e.g., forest). The n-alkane biomarker results in the modern soil profiles showed, the average chain length (ACL) and (nC31+nC33)/(nC27+nC29) ratio are very efficient parameters for reconstruction of vegetation, therefore these parameters were used to unravel the palaeovegation in loess-palaeosol sequences. In both sections n-alkane biomarkers studies showed vegetation changes in different periods. These changes were most intense in Nowdeh loess-palaeosol sequence, so grassland and shrub in profil1 (Bk horizon) and profile 2 (ABk horizon) palaeosols (with illite dominance) changes to forest in profile 2 (AB horizon with smectite dominance) and profile 3 (Btky horizon with smectite dominance and vermiculite presence) palaeosols. Agh Band section had one palaeosol including two horizons (Bw and Bk) which based on n-alkane specifications the Bw-horizon indicates grass/shrub vegetation (alsosmectite presence). It could indicate favorable environmental conditions promoting the growth of more dense vegetation.
Conclusions: Results showed that clay mineralogy changes are in line with n-alkane biomarkers results and both analyses reflect climate and environment conditions in soil formation periods and they are more effective for the accurate reconstruction of palaeoenviroment. According to chronological data for Nowdeh and Agh Band loess-palaeosol sequences, Nowdeh section had more suitable environment (more precipitation, more dense vegetation and suitable conditions for formation and development of soil, pedologically) compared with Agh Band section at the same times. Clay mineralogy and n-alkane biomarker resulted in the modern soil profiles and loess-palaeosol sequences showed that the modern ecological gradient (especially for precipitation) existed during the time and climate was an important soil formation factor in the studied region.

Keywords

1- Amini Jahromi, H., Naseri, M.Y., Khormali, F., and Movahedi Naeini, S.A.R. 2008. Clay mineralogy of the soil formed on loess parent material in two regions of Golestan Province. Journal of Agricultural Sciences and Natural Resources.15:5.18-27.(in Persian)
2- Bai Y., Fang X.M., Nie J.S., Wang Y.L., and Wu F.L. 2009. A preliminary reconstruction of the paleoecological and paleoclimatic history of the Chinese Loess Plateau from the application of biomarkers. Palaeogeography, Palaeoclimatology, Palaeoecology, 271: 161–169.
3- Bouyoucos G.J. 1962. Hydrometer method improved for making particle size analysis of soils. Agronomy Journal. 54: 464-465.
4- Bronger A., Winter R., and Sedove S. 1998. Weathering and clay mineral formation in two Holocene soils and buried paleosols in Tadjikistan: towards a Quaternary paleoclimatic record in Central Asia. Catena, 34: 19-34.
5- Bull I.D., van Bergen P.F., Nott C.J., Poulton P.R., and Evershed R.P. 2000. Organic geochemical studies of soils from the Rothamsted Classical Experiments – V. The fate of lipids in different long-term experiments. Organic Geochemistry, 31: 389–408.
6- Djamali M., de Beaulieu J.L., Shah-hosseini M., Andrieu-Ponel V., Ponel P., Amini A., Akhani H., Leroy S.A.G., Stevens L., Lahijani H., and Brewer S. 2008. A late Pleistocene long pollen record from Lake Urmia, Iran. Quaternary Research, 69: 413–420.
7- Douglas L.A. 1989. Vermiculites. In: Dixon, J.B., Weed, S.B. (Eds.), Minerals in Soil Environments, second ed. Soil Science Society of America, Madison, WI, 635-674 pp.
8- Egli M., Mirabella A., and Sartori G. 2008. The role of climate and vegetation in weathering and clay mineral formation in late Quaternary soils of the Swiss and Italian Alps. Geomorphology, 102: 307-324.
9- Frechen M., Kehl M., Rolf C., Sarvati R., and Skowronek A. 2009. Loess chronology of the Caspian Lowland in Northern Iran. Quaternary International, 128: 220-233.
10- Ghafarpour A. 2012. Evolution and characteristics of modern soils compared to underlain paleosols in a precipitation gradient in Golestan province. M.Sc. thesis. Soil science Dep. Gorgan University of agriculture sciences and natural resources. 82 pp.
11- Jackson M.L. 1975. Soil Chemical Analysis. Advanced Course. University of Wisconsin, College of Agriculture, Department of Soils, Madison, Wisconsin, USA.
12- Jeong G.Y., Hillier S., and Kemp R.A. 2011. Changes in mineralogy of loess–paleosol sections across the Chinese Loess Plateau. Quaternary Research, 75: 245–255.
13- Johns W.D., Grim R.E., and Bradley W.F. 1954. Quantitative estimation of clay minerals by diffraction methods. J. Sediment Petrology, 24: 242-251.
14- Karimi A., Frechen M., Khademi H., Kehl M., and Jalalian A. 2011. Chronostratigraphy of loess deposits in northeast Iran. Quaternary International, 234: 124–132.
15- Kehl M. 2009. Quaternary climate change in Iran – the state of knowledge. Erdkunde, 63: 1–17.
16- Kehl M. 2010. Loess, loess-like sediments, soils and climate change in Iran. Relief, Boden, Paläoklima 24, 208 pp.
17- Kehl M., Sarvati R., Ahmadi H., Frechen M., and Skowronek A. 2005. Loess paleosol-sequences along a climatic gradient in Northern Iran. Eiszeitalter und Gegenwart, 55: 149–173.
18- Khormali F., and Abtahi A. 2003. Origin and distribution of clay minerals in calcareous arid and semi-arid soils of Fars Province, southern Iran. Clay Minerals, 38: 511-527.
19- Khormali F., and Kehl M. 2011. Micromorphology and development of loess-derived surface and buried soils along a precipitation gradient in Northern Iran. – Quaternary International, 234: 109–123.
20- Kittrick J.A., and Hope E.W. 1963. A procedure for particle size separation of soils for X-ray diffraction analysis. Soil Science, 96: 312-325.
21- Lei G.L., Zhang H.C., Chang F.Q., Pu Y., Zhu Y., Yang M.S., and Zhang W.X. 2009. Biomarkers of modern plants and soils from Xinglong Mountain in the transitional area between the Tibetan and Loess Plateaus. Quaternary International, 218: 143–150.
22- Mehra O.P., and Jackson M.L. 1960. Iron oxide removal from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate. Clays Clay Minerals, 5: 317-327.
23- Muhs D.R. (2013). The geologic records of dust in the Quaternary. Aeolian Research, 9: 3–48.
24- National soil survey center .2012. Field book for describing and sampling soils, Ver. 3. U.S. department of agriculture, Natural resources conservation service.
25- Page A.L., Miller R.H., and Keeney D.R. 1982. Methods of Soil Analysis. Part 2. Chemical and Microbiological Properties, second ed. Agronomy Monographs, 9. ASA-SSA, Madison, Soil Sci. Soc. Am. J. 51: 1173-1179.
26- Pecsi M. 1990. Loess is not just the accumulation of dust. Quaternary International, 78: 1-12.
27- Schaetzl R.J. and Anderson S. 2005. Soils: Genesis and Geomorphology. Cambridge University Press. 833 pp
28- Schwark L., Zink K., and Lechterbeck J. 2002. Reconstruction of postglacial to early Holocene vegetation history in terrestrial Central Europe via cuticular lipid biomarkers and pollen records from lake sediments. Geology, 30: 463–466.
29- Shahriari A., Khormali F. and Azarmdel H. 2012.Clay mineralogy of Mollisols and Mollisols-like soils as affected by physiography unit form on loess deposits in southern Gorgan River, Golestan province ,Journal of Water & Soil Conservation, 18(4) :80-63.
30- Sheldon N.D., and Tabor N.J. 2009. Quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols. Earth Science Reviews, 95:1–52.
31- Soil Survey Staff. 2014. Keys to soil Taxonomy, 12th ed. U.S. department of agriculture, Natural resources conservation service.
32- Vlaminck S., Rolf C., Shahriari A., Khormali F., Frechen M., and Kehl M. 2013. The Loess-soil sequence at Now Deh (Northern Iran) and its palaeoclimatic implications deduced from magnetic susceptibility and grain size records. Research for desert margin regions Conference. February 2013. Rauischholzhausen, Germany.
33- Walkley A. and Blak I.A. 1934. An Examination of the method for determining Soil organic matter and a proposed modification of the Chromic Acid titration method. Soil Science, 34: 29-38.
34- Zech M., and Glaser B. 2008. Improved compound-specific ᵟ13C analysis of n-alkanes for application in palaeoenvironmental studies. Rapid Communications in Mass Spectrometry, 22 (2): 135-142.
35- Zech M., Rass S., Buggle B., Löscher M., and Zöller, L. 2012. Reconstruction of the late Quaternary paleoenvironments of the Nussloch loess paleosol sequence, Germany, using n-alkane biomarkers. Quaternary Research, 78: 226–235.
36- Zech M., Krause T., Meszner S., and Faust, D. 2013. Incorrect when uncorrected: Reconstructing vegetation history using n-alkane biomarkers in loess-paleosol sequences - A case study from the Saxonian loess region, Germany. Quaternary International, 296: 108-116.
37- Zhou W., Xie S., Meyers P.A., and Zheng Y. 2005. Reconstruction of late glacial and Holocene climate evolution in southern China from geolipids and pollen in the Dingnan peat sequence. Organic Geochemistry, 36: 1272–1284.
CAPTCHA Image