Scientific registration n : 60 Symposium n : 22 Presentation : poster. LIU Jen-Chyi (1) and CHEN Zueng-Sang (2)

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1 Scientific registration n : 60 Symposium n : 22 Presentation : poster Mineral Transformation and Weathering Sequence of Loamy Spodosols in Taiwan Transformations minérales et séquence d'altération d'un podzol limoneux à Taiwan LIU Jen-Chyi (1) and CHEN Zueng-Sang (2) (1) Department of Agricultural Chemistry, Taiwan Agricultural Research Institute, Taichung, Taiwan 41301, Republic of China (2) Graduate Institute of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan 10617, Republic of China INTRODUCTION Spodosols are characterized by a spodic horizon which was dominant with active amorphous materials composed of organic matter and aluminum, with or without iron (Freeland and Evans, 1993; Mokma, 1993). Podzolic soils of Taiwan are distributed mostly on the Central Ridge which the environmental conditions are cool and humid climate and have coniferous vegetation types (Chen, 1990; Liu and Chen, 1990). These soils have low ph in surface horizons (A and E horizons) and high accumulation of Fe, Al and organic carbon in B horizons. The clay mineralogy in the albic horizon of Spodosols is dominant with smectite and/or vermiculite in the temperate regions (Ross et al., 1990). Available information indicates that smectite and vermiculite in E horizon are formed from non-expanding layer silicates including illite, chlorite and hydroxyinterlayered vermiculite (HIV) (Gjems, 1970; Chang, 1971; Ross, 1975; Adams, 1976), but Spodosols in Taiwan are lack of smectite in E horizon. The objectives of this study are (1) to understand the composition and distribution of clay minerals in the Spodosols in central Taiwan, and (2) to explain the alteration and formation of clay minerals in the studied area. MATERIALS AND METHODS Sampling sites Two loamy Spodosols were collected along the Chun-Ta forest road near Wuang- Hsiang Mountain in central Taiwan (23 o 37'N, 120 o 56'E). The environmental conditions of two pedons are shown in Table 1. In the study area, annual temperature, precipitation and relative humidity are 12.7, 2000 mm, and 72%, respectively. The soil moisture regime and soil temperature regime belong to udic and mesic, respectively. At present, two pedons were covered with a man-made forest mainly consisted with Pinus taiwonensis and Tsuga chinensis species. 1

2 Table 1. The environmental conditions of two soil pedons. Soil Sampling Elevation Slope Facing Geomor- SMR * STR ** Parent Vegetation types No. Site phology material (m) (%) (degree) 1 23 o 37'23"N S175 Footslope Udic Mesic Slate Pinus taiwonensis 120 o 55'01"E Sandstone Cryptomeria japonica Chamecyperis formosensis 2 23 o 36'48"N N35 Backslope Udic Mesic Slate Tsuga chinensis 120 o 56'06"E Sandstone Rhododendron Pseudochrysanthum Miscanthus transmorrisonensis * SMR: Soil moisture regime, ** STR: Soil temperature regime. Soil analysis Soil samples were air-dried and ground to pass a 2 mm sieve. Soil ph was determined by glass electrode in a soil/water ratio of 1:1 (Mclean, 1982). Organic carbon was determined by Walkley-Black wet combustion method (Nelson and Sommers, 1982), and particle size analysis was determined by pipette method (Gee and Bauder, 1986). Exchangeable K, Na,Ca, and Mg were exchanged by ammonium acetate method and determined by AA. (Thomas, 1982). Exchangeable Al was determined by Barnhisel and Bertsch method (1982). Selected chemical properties of Fe and Al was extracted with 0.2M oxalic acid (ph 3) (McKeague and Day, 1966), 0.1M sodium pyrophosphate (ph 10) (Loveland and Digby, 1984), and the optical density of oxalate extractable values (ODOE) were determined at 430 nm by spectrophotometry (Daly, 1982). Semi-quantitative identification of Clay minerals The clay fraction (<2 micrometer) was separated and collected after the removal of organic matter and free oxides of iron and aluminum by treated with H 2 O 2 and CBD method (Mehra and Jackson, 1960), respectively. X-ray diffraction (XRD) analysis was performed on oriented K- and Mg-saturated clay samples and 6N HCl treated clay samples. Expansion mineral was identified for the Mg-saturated samples treated with ethylene glycol saturation. The K-saturated samples were further subjected to successive heating treatment in 350 and 550 for 2 hr. Clay samples were scanned at 2 degree/minute by a Rigaku Miniflex diffractometer. Identification and semi-quantitative determination of the clay minerals were calculated based on the XRD intensity of the clay samples with different treatments. RESULTS AND DISCUSSION Soil properties The physical and chemical properties of two pedons are shown in Table 2. Weathering soils derived from slate and sandstone parent material are characterized by high clay content ranged from 300 to 350 g/kg in the Bhs horizon of Podzolic soils in subalpine forest region (Liu et al., 1994; Chen et al., 1995). The soil ph are ranged from 3.8 to 4.9, which increased with increasing soil depth. Organic carbon content and pyrophosphate extractable Fe and Al are low in E horizon and significantly increased in the Bhs horizon. The exchangeable cations and base saturation percentage in two 2

3 pedons are very low, however, exchangeable aluminum and Al saturation percentage in soils are higher than other cations, which are caused by strong leaching processes. Soil classification According to Keys to Soil Taxonomy (Soil Survey Staff, 1996), two pedons can be classified as Spodosols (Table 3). The organic carbon content in Bhs horizon was higher than 6% and the thickness of spodic horizons was more than 10 cm. Pedon-1 was further classified as Haplohumod. However, pedon-2 only have 52 g/kg of organic carbon content in the Bhs horizon and is classified as Haplorthod. Compositions and transformation of clay minerals The clay mineral composition and their distributions in two pedons are summarized in Table 4. The major clay mineral in the E horizon of two pedons was illite and minor with vermiculite, kaolinite, mixed layer minerals, and quartz. In the Bhs horizon of these two pedons, illite, vermiculite and hydroxy-interlayered vermiculite (HIV) are the main clay minerals. Minor amounts of kaolinite, quartz and feldspar were also present in the Bhs horizon. XRD patterns of two pedons also indicated that illite, hydroxyinterlayered vermiculite, and chlorite are the dominant clay minerals in BC horizon. According to some basic geological studies in Taiwan, parent materials in this area mainly composed with illite, chlorite, and minor with kaolinite. Table 2. The physical and chemical properties of two pedons. Hori- Depth Total Texture ph Organic CEC Sum Base Al # zon sand silt clay H2O carbon cations Satu. Satu. (cm) g/kg g/kg - - cmol(+)/kg % ---- Pedon-1 : Fine-loamy, mixed, mesic, Typic Haplohumod O/A CL E L BE CL Bhs SiCL Bs CL BC CL BC2 > SCL Pedon-2: Fine-loamy, mixed, mesic, Typic Haplorthod O/A L E L BE CL Bhs CL Bs CL Bs CL Bs CL BC > SCL # Al saturation percentage (%)= [ex. Al/(ex. Al + ex. bases)] x 100% 3

4 Table 3. The selected properties in E and Bhs horizons of two pedons. Horizon Depth Munsell color O.C. Fe p + Al p + ODOE # Al o +1/2Fe o * (cm) - g/kg g/kg % ---- Pedon-1 : Fine-loamy, mixed, mesic, Typic Haplohumod E YR 7/1(85%) YR 6/4(15%) Bhs YR 4/ Pedon-2 : Fine-loamy, mixed, mesic, Typic Haplorthod E YR 7/ YR 6/6(mottle) Bhs YR 4/ YR 2.5/2(mottle) +: Sodium pyrophosphate (ph 10) extractable aluminum and iron. #: ODOE: optical density of oxalate extraction, *: oxalate extractable Al and Fe. Previous studies have shown that the composition of soil solution derived from mica may drastically influence the nature of the weathering product (Vicente et al., 1977). The high organic matter content and low soil ph indicate that organic acids have a high potential effects on the weathering products of clay mineral in the study area. XRD patterns in E or B horizons of two pedons indicate that illite-vermiculite or chlorite-vermiculite mixed layers are the main minerals derived from chlorite. In nature condition, leaching process and plant uptake decrease the concentration of potassium in the soil solution. The release of K from the interlayer of illite or chlorite promote the formation of vermiculite. In the study area, minor amounts of chlorite was found in BC horizon of two pedons. This result implied that chlorite was more easily weathered than illite. HIV formed in these Spodosols can be regarded as a weathering product derived from chlorite, or more commonly, derived from the deposition of hydroxy-al polymeric compounds within the interlayer of vermiculite. This proposal was coincided with the result of previous study (Barnhisel and Bertsch, 1989). 4

5 Table 4. Clay mineral composition # of two pedons. Horizon Chl Ver HIV Ill Sme M-L Kao Qz Fld Gib Pedon-1 E Bhs Bs BC BC Pedon-2 E Bhs Bs Bs Bs BC # Chl: Chlorite, Ver: Vermiculite, HIV: Hydroxy interlayer Vermiculite, Ill: Illite, Sme: Smectite, M-L: Mixed layer clay minerals, Kao: Kaolinite, Qz: Quartz, Fld: Feldspar, Gib: Gibbsite. +++: dominate, ++: moderate, +: miner, : trace Weathering sequence Some water-soluble organic substances (especially for fulvic acid) formed from litter decomposition in the upper part of pedon and complexed with Fe and Al, then translocated into the spodic horizon of Spodosols (McKeague et al., 1983). The continuous removal of solubilized Fe and Al by leaching process from E horizon will provide a favorable gradient by weathering processes. Then, extreme acid conditions and high organic matter content in the two pedons will facilitate the transformation of clay minerals changed from chlorite and illite to HIV and finally changed to vermiculite. In past studies, we found that the relative high concentration of pyrophosphate-extractable Fe-, and/or Al-organic complexes formed in the Bhs horizon of Spodosols in central Taiwan near this study area (Li et al., 1998). Some soluble aluminum was eluviated from E horizon and illuviated into the interlayer of vermiculite in the Bhs horizon and formed to HIV. CONCLUSIONS A simplified statement of clay mineral weathering sequence in loamy Spodosols in central Taiwan are discussed. Illite and chlorite are dominant minerals in the parent material. In the albic (E) horizon, chlorite-vermiculite interstratified minerals underwent structural alternation and K was released from the interlayers of minerals. In the Bhs or Bs horizons, these clay minerals underwent additional structural changes and vermiculite was formed and interstratified minerals are also derived from chlorite or illite. Therefore, the weathering sequence of clay minerals in these two pedons is shown as: illite, chlorite chlorite-vermiculite interstratified minerals or HIV vermiculite. 5

6 REFERENCES Adams, W.A Experimental evidence on the origin of vermiculite in soils on lower Palaeozoic sediments. Soil Sci. Soc. Am. J. 40: Barnhisel, R. I. and P. M. Bertsch Aluminum. p In A. L. Page, et al. (eds.), Methods of soil analysis, Part 2. Chemical and microbiological properties. 2nd ed. Agronomy monograph 9. Barnhisel, R. I. and P. M. Bertsch Chlorites and hydroxy-interlayered vermiculite and smectite. p In J. B. Dixon and S. B. Weed, (eds.), Minerals in soil environments. 2nd ed. Soil Sci. Soc. Am., Madison, WI. Chang, J. M Clay mineralogy and related chemical properties of podzolic soils in Taiwan. J. Chinese Agric. Chem. Soc. 9: (in Chinese, with English abstract and table). Chen, Z. S Spodosols of Taiwan. p In J. M. Kimble and R. D. Yeck, (eds.), Proceedings of the 5th International Soil Correlation Meeting (V-ISCOM): Characterization, Classification and Utilization of Spodosols. USDA -SCS and Soil Management Support Service. Chen, Z. S., J. C. Liu, and H. C. Chiang Soil properties, clay mineralogy, and genesis of some alpine forest soils in Ho-Huan Mountain area of Taiwan. J. Chinese Agric. Chem. Soc. 33: Daly, B. K Identification of podzols and podzolized soils in New Zealand by relative absorbance of oxalate extracts of A and B horizons. Geoderma 28: Freeland, J. A. and C. V. Evans Genesis and profile development of Success soil, Northern New Hampshire. Soil Sci. Soc. Am. J. 57: Gee, G. W. and J. W. Bauder Partical size analysis. p In A. Klute, (editor), Methods of soil analysis, Part 1. Physical and mineralogical methods. 2nd ed. Agronomy monograph 9. Gjems, O Mineralogical composition and pedogenic weathering of the clay fraction in podzol soil profiles in Zalesine, Yugoslavia. Soil Sci. 110: Li, S. Y., Z. S. Chen, and J. C. Liu Subalpine loamy Spodosols in Taiwan: Characteristics, micromorphology, and genesis. Soil Sci. Soc. Am. J. Vol. 62 (Accepted). Liu, J. C., J. H. Yang, H. C. Chiang, H. Y. Guo, and Z. S. Chen Properties, clay mineralogy and pedogenic processes of two mountain forest soils in Chi- Lan Area, Taiwan. J. Chinese Agri. Chem. Soc. 32: (in Chinese, with English abstract and table). Liu, J. T. and Z. S. Chen Characteristics, genesis and classification of podzolic soils in Tamanshan mountain, northern Taiwan. J. Chinese Agric. Chem. Soc. 28: (in Chinese, with English abstract and table). Loveland, P. J. and P. Digby The extraction of Fe and Al by 0.1M pyrophosphate solutions: a comparison of some techniques. J. Soil Sci. 35: Mclean, E. O Soil ph and lime requirement. p In A. L. Page, et al. (eds.), Methods of soil analysis, Part 2. Chemical and microbiological properties. 2nd ed. Agronomy monograph 9. McKeague, J. A. and J. H. Day Dithionite and oxalate extractable Fe and Al as acids in different various classes of soils. Can. J. Soil Sci. 46: McKeague, J. A., F. De Coninck, and D. P. Franzmeier Spodosols. pp In L. P. Wilding, N. E. Smeck, and G. F. Hall, (eds.), Pedogenesis and Soil Taxonomy, II. The Soil Orders. Elsevier Sci. Publ. Comp., New York, U.S.A and Amsterdam, The Netherlands. Mehra, O. P. and M. L. Jackson Iron oxides removed from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate. Clays Clay Miner. 7:

7 Mokma, D. L Color and amorphous materials in Spodosols from Michigan. Soil Sci. Soc. Am. J. 57: Nelson, D. W. and L. E. Sommers Total carbon, organic carbon, and organic matter. p In A. L. Page, et al. (eds.), Methods of soil analysis, Part 2. Chemical and microbiological properties. 2nd ed. Agronomy monograph 9. Ross, G. J Experimental alteration of chlorites into vermiculite by chemical oxidation. Nature 255: Ross, G. J., C. Wang, and H. Kodama Mineralogy of Spodosols. p In J. M. Kimble and R. D. Yeck (eds.), Proceedings of the 5th International Soil Correlation Meeting (V-ISCOM): characterization, classification and utilization of Spodosols. USDA-SCS and Soil Management Support Service. Soil Survey Staff Keys to Soil Taxonomy. 7th Edition. NRCS-USDA. Thomas, G. W Exchangeable cation. p In A. L. Page, et al. (eds.), Methods of soil analysis, Part 2. Chemical and microbiological properties. 2nd ed. Agronomy monograph 9. Vicente, M. A., M. Razzaghe, and M. Robert Formation of aluminum hydroxy vermiculite (intergrade) and smectite from mica under acidic conditions. Clay Min. 12: Keywords : Loamy Spodosols, Clay minerals, Weathering sequence, Hydroxyinterlayer vermiculite (HIV) Mots clés : podzols limoneux, minéraux argileux, séquence d'altération, vermiculite hydroxyalumineuse 7