EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7

Transition Soils between Spodosols and Ultisols in Subalpine Forest of Taiwan

CHEN1 Zueng-Sang, HSEU2 Zeng-Yei, WU1 Sen-Po and TSAI1 Chen-Chi 1Department of Agricultural Chemistry, National Taiwan UniversityTaipei 106-17, Taiwan. E-mail: [email protected] 2Department of Environmental Science and Technology, National Pingtung University of Science and Technology Pingtung 912-01, Taiwan.

Abstract Seven transitional soils were selected to investigate the transition of Spodosols and Ultisols in the subalpine forests of Taiwan whose elevations range from 1900 m to 2700 m and have udic soil moisture regimes and mesic soil temperature regimes. The selected transitional forest soils include seven Ultic Spodosols based on USDA Soil Taxonomy, or seven Podzols based on the World Reference Base classification system. The soils with gentle landscape with <10% of slope are derived from sandstone and shale. The study area experiences a cool and humid climate with very high annual rainfall, ranging from 3000 to 4500 mm. The vegetation is coniferous vegetation dominated by Taiwan red cypress, Taiwan red pine, and peacock pine. The transition soils of Spodosols and Ultisols in Taiwan are specially characterized by loamy or clayey soil texture classes in the B horizon with clay contents ranging from 250 to 400 g/kg. High rainfall promotes the formation of these transition soils associated with strong illuviation of clay, organic carbon, free iron oxides, or organo-metallic complexes. We propose that vegetation, climate, and parent materials strongly influence the multiple pedogenic processes of the transition soils between Ultisol and Spodosols in Taiwan. Clay illuviation processes and podzolization are the two dominant pedogenic processes in these transition soils identified by field morphology, micromorphology and laboratory analysis. Stronger illuviation of spodic materials was found in these transition soils where clay illuviation also occurred. Organo-metallic complexes were progressively accumulated on the surface of illuvial clays or coagulated as spodic pellets when podzolization occurred later in the subsurface horizons. Consequently, although the clays were slowly leached into the Bhs horizons within 50-cm depth, the pure clays were easily leached downward deeper in this study. We recommend that argillic great groups of Humods and Orthods with Ultic subgroups be added to Spodosols in the USDA Soil Taxonomy system for soils with evidience of illuvial clay in or below spodic horizons such as the transitional soils studied in Taiwan.

Keywords: Transition soils, Spodosols, Ultisols, Subalpine forest, Clay illuviation, Podzolization. Introduction While theories of illuviation of spodic materials have largely emphasized chemical rather than clay translocation, some studies have demonstrated soil particle as well as chemical migration in podzolic soils (Harris and Hollien, 1999). The texture of parent material and drainage condition strongly influenced the direction of soil development on the Coastal Plain of the eastern United States of America, accounting for why the two commonly used pedogenic pathways resulted in distinctly different soils as Ultisols with spodic (Bhs) horizons or Spodosols with argillic (Bt) horizons (Markewich and Pavich, 1991). Spodosols generally have a surface horizon of accumulated organic matter, a bleached eluvial horizon, and a reddish or brown-black illuvial spodic horizon (Lundstrom et al., 2000). These soils are often found not only in loamy or coarser materials, but also in subpolar and alpine climatic regimes; however, in some regions, they extend into the interiors of mid-latitude continents (Li et al., 1998). Two processes have been

Spodosols and Ultisols in Subalpine Forest of Taiwan. Chen et al. 137 EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7 proposed to explain podzolization: (i) formation and downward transport of complexes of organic acids with Al and Fe, and (ii) silicate weathering followed by downward transport of Al and Si as inorganic colloidal sols (Lundstrom et al., 2000).

Ultisols and Spodosols of Taiwan are found in the subalpine and alpine forests in udic or perudic soil moisture regimes and mesic soil temperature regime with heavy rainfall (> 3000 mm/yr). However, Spodosols and Ultisols are generally formed on the flatter summits and backslopes in microrelief positions (Li et al., 1998;). Some studies identified the pedogenic processes of Spodosols in the subalpine forests of the Central Ridge in Taiwan (Chen et al., 1995; Li et al., 1998). Li et al. (1998) also indicated that spodic material formation and clay translocation occurred in the Bhs horizons of loamy Spodosols in central Taiwan. The characteristics of Spodosols in Taiwan significantly differ from those of North American and European countries in terms of soil texture. Taiwan’s Spodosols are derived from fine-textured materials weathered from rocks such as sandstone, shale and slate under heavy annual rainfall that intensifies the leaching processes. Therefore, according to the related investigations, the clay contents in the studied Spodosol or podzolic soils are generally more than 30%, and both podzolization and clay illuviation occur in these soils of Taiwan (Chen et al., 1995; Hseu et al., 1999). In particular, understanding the illuviation of spodic materials in the Ultisols of the subalpine forests at the Alishan Mountain of central Taiwan is of relevant interest. The objectives of this study are: (i) to describe the field morphology and micromorphology related to spodic materials and clay illuviation in the seven transition soils of Spodosols and Ultisols, (ii) to interpret the formation of spodic and argillic horizons in the subalpine forest soils, and (iii) to evaluate the pedogenic model of the transition soils of the study area. Materials and Methods

Site description Three Spodosol pedons (pedons 901 to 903) were selected in the coniferous forest of the Alishan Mountain with slopes ranging from 5 to 18%. The Alishan Mountain, which is an important subalpine forest of Taiwan, is located in the central-western part of the island. The secondary vegetation types were established after deforestation nearly a century ago. These subalpine forest soils at elevations from 1500 to 3000 m are derived from marine argillaceous sediments and interstratified sandstone and shale of the late Miocene to early Pliocene. The overstory vegetation is dominated by red cypress (Chamaecyparis formosensis and Tsuga chinensis), and to a lesser extent by pine (Pinus armandii). The understory vegetation is dominated by Yushania niitakayanensis, Polygonum Chinese, and Miscanthus floridulus. The annual rainfall is about 4000 mm and most of it falls from May to September. The annual air temperature is o 10.6 C. The soil moisture regime is udic or perudic and the soil temperature regime is mesic in the study area.

o o Four Spodosols (pedon JL-1 to JL-4) were sampled in the Jen-Lun forestry area (N23 42', E120 56') in Nantou county, central Taiwan. These pedons were located within a radius of 600 m of each other, and elevation of the pedons ranged from 2400 m to 2700 m. The mean annual air temperature, annual rainfall o and relative humidity are 12.7 C, >3000 mm, and 72%, respectively. About 76% of the annual rainfall intensively falls from May to September. The soil moisture regime and soil temperature regime are udic and mesic, respectively. The parent materials consist of shale and slate. The native vegetation is dominant with Tsuga chinensis Pritz, but after cutting and burnning of the native forest, the secondary forests are dominantly Pinus taiwanensis Hayata, Yusania niitakayamensis (Hay.) Keng F., and Miscanthus transmorrisonensis Hayata. At the time of sampling, the four pedons had a cover of secondary forest consisting mainly of Chamaecyparis formosensis Matsum and Cryptomeria japonica (L.f.) D. Don species planted by the Taiwan Forestry Bureau in the 1950s. Soil analysis Soil samples were collected from each horizon of the profiles for physical and chemical analyses as follows: particle size distribution was determined by the pipette method; the pH of air-dried samples (< 2 mm) on a mixture of soil/deionized water (1:1) by glass electrode; organic carbon (OC) content by the Walkey-Black wet oxidation method; Cation exchange capacity and exchangeable bases with the ammonium acetate method (pH 7.0); free Fe (Fed), and Al (Ald) by the dithionite-citrate-bicarbonate (DCB) method (Mehra and Jackson, 1960); Amorphous Fe (Feo) and Al (Alo) by 0.2 M ammonium oxalate (pH 3.0) (McKeague and Day, 1966); Organic-bound Fe (Fep) and Al (Alp) by 0.1 M sodium pyrophosphate (pH 10.0) (Loveland and Digby, 1984). Finally, all metals were determined by atomic absorption

138 Spodosols and Ultisols in Subalpine Forest of Taiwan. Chen et al. EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7 spectrometry (AAS) (Hitachi, 180-30 type). Optical density of oxalate extract (ODOE) was determined by the method developed by Daly (1982). Kubiena boxes for micromorphology were used to collect undisturbed soil blocks in the field. After air drying, vertical oriented thin sections with a thickness of 30 μm were prepared by Spectrum Petrographics, Inc., Oregon, USA. Thin sections were observed by polarized microscopy and describing the micromorphology according to the terminology of Bullock et al. (1985). Results and Discussion

Field morphology Although the three pedons of the Alishan area are located on different landscape positions, they are classified as Ultic Spodosols with the sequences of O-A-E-Bhs-C based on Soil Taxonomy (Soil Survey Staff, 1999). Distinct surface layers (O&O/A) more than 10-cm in thickness were found in the three Spodosols (Table 1). The colors were gray or light gray with chroma 1 in all albic horizons, but the colors were strong brown or brown yellow in all spodic or argillic horizons of these pedons. All albic horizons were sandy loam, but the spodic or argillic horizons were sandy clay loam to clay. The strong brown spodic horizons, found within 50-cm depth, were underlain by similarly colored Bt horizons in the three pedons. It was difficult to identify clay coatings by naked eyes, but discontinuous few and common clay coatings were found in all Bhs and Bt horizons by hand lens in the field. The four pedons of the Jen-Lun forestry area all have dark organic/mineral (O/A) surfaces, well-developed albic (E) horizons and spodic (Bh) horizons (Table 1). The dominant color of the spodic horizon is strong brown or dark brown (7.5YR 4/6 or 7.5YR 3/4); these spodic materials qualify the pedons as Spodosols based on the color criteria of spodic materials as defined in Soil Taxonomy (Soil Survey Staff, 1999). Micromorphology In thin sections, fresh roots, humified substances mixed with broken cell walls, fecal pellets or amorphous organic materials were found in the O or O/A horizons of pedons 901 to 903. Charcoal fragments retaining decomposed cellular structures were found in the surface soils, indicating that fire events had occurred in the study area. Bullock and Clayden (1980) indicated that pellet microstructure is found in both coarse and fine textured Spodosols and it is also common in some finer textured Spodosols that lack cracked coatings. In the present study, the micromorphological characteristics of the spodic horizons in all pedons showed distinct dark pellets and poorly oriented illuvial clay along the irregular voids. For example, in the Bhs horizon of pedon 901, the dominant pedofeatures were organo-metallic complexes shown as pellets or aggregates-like on coarse grains and pedsurfaces (Fig. 1a). Surprisingly, organo-metallic and clay accumulations were both observed by the pellets and clay coatings. But these illuvial clays have a relatively weak birefringence masked by amorphous materials (Fig. 1b). Similarly, both organo-metallic complexes and clay coatings were found in the Bhs and Bt horizons of all pedons, and there were organo-metallic pellets in voids and on pedsurfaces (Fig. 1c).

The dominant pedofeatures in the Bt horizon of pedon 902 were oriented clay coatings along root channels (Fig. 1d). Illuvial clays were observed as various types in all subsurface horizons, like grain coatings, hypocoatings along the root channels and infillings in the larger packing voids. These illuvial clays have relatively weak birefringence caused by organo-metallic complexes, especially when they were found in Bhs horizons. Grain coatings and large pellet-like aggregates, resulting from clay, Fe and organic matter mixtures (Fig. 1d) were found in the Bt horizons of pedons 901 and 902. Pellety fabrics were mainly found in the Bhs horizons of all pedons (Fig. 1e). Surprisingly, large clay coatings >1% in thin section, darkened by organo-metallic complexes, were also found in all Bhs horizons (Fig. 1f). Based on micromorphology, we can infer that clay illuviation and spodic material formation occurred simultaneously in most parts of this humid region. Physical and chemical properties All pedons have fine textures in the subsurface horizons, except for pedon JL-1 (Table 2). The pH values of all soils are less than 5.0, and they are significantly lower than the pH value defined in spodic materials (pH 5.9). Organic C has the greatest accumulation in the surface organic horizon, decreases in the E horizon, and increases again in the Bhs or Bh horizon. This indicates that organic carbon has been eluviated from albic horizons and accumulated in the spodic horizons. Cation exchange capacity follows the same trend as OC. Extremely low base saturation of the soils, ranging from 1 to 10% in all pedons is associated with the dominantly acidic parent rocks and a high rainfall, strong leaching environment.

Spodosols and Ultisols in Subalpine Forest of Taiwan. Chen et al. 139 EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7

The distribution of Fe and Al The depths of maximal extractable Fe and Al are commonly found in the Bhs or Bh horizons of the seven pedons (Table 2). It indicates significant illuviation and accumulation of Fe and Al from E horizons into spodic horizons. The DCB extractable Fe contents are much higher than oxalate and pyrophosphate extractable ones identified by the Fep/Fed and Feo/Fed values. It is noticed that most pyrophosphate extractable Fe and Al contents are higher than oxalate ones within the same horizons. High ratios of Fep/Feo and Alp/Alo in the B horizons of the seven pedons, more than 1.0, suggest that much of the non- crystalline Fe and Al exist in organic bound form (Table 2). Bockheim et al. (1996) also showed a similar trend between these two extractions for Ultic Spodosols in Oregon, but their average ODOE values of the subsurface horizons were much less than those in this study. Although Al is more mobile than Fe in soil, the depth functions of extractable Al are similar to those of Fe in this study. In pedons JL-2, JL-3 and JL-4, the dominant color of the B horizons is 7.5YR 4/6. According to Soil Taxonomy (Soil Survey Staff, 1999), the chemical characteristics of the B horizons of these pedons must indicate that enough spodic materials in the subhorizons have been accumulated to classify them as Spodosols. The ODOE values of B horizons are more than 0.25, and each value is at least two times as high as the ODOE value of an overlying eluvial horizon (Table 2). Furthermore, in the B horizons of the seven pedons, total aluminum plus half the iron content extracted by ammonium oxalate is much higher than 0.5, and each value is also at least two times as high as that value for an overlying eluvial horizon (Table 2). These increased ODOE values and Alo+1/2Feo (%) in the upper part of the B horizons indicate that the translocation and accumulation of spodic materials such as organic matter, Fe, and Al have occurred in illuvial horizons of these Spodosols.

All the subsurface horizons satisfy the criteria of chemical properties defined for a in Bhs horizon. Pyrophosphate extractable Fe and Al values correlate well with OC values (r2 = 0.71 and 0.83, p<0.05) for all the eluvial and illuvial horizons (n=15) of the pedons 901, 902, and 903. Our results further indicate that the clay content correlates well not only with pyrophosphate extractable Fe and Al (r2 = 0.68 and 0.74, p<0.05), but also with DCB extractable Fe and Al (r2 = 0.65 and 0.73, p<0.05). The relatively high r2 values suggest that illuvial Fe and Al are significantly bound with organic matter and then adsorbed after their translocation. Therefore, although these organo-metallic complexes may adsorb or precipitate within the finer matrix formed by the illuvial particles, they only move down a short distance. Pedogenic model Spodic material illuviation and clay translocation occurred in the three soils of the Alishan area (pedons 901 to 903) identified by field morphology, micromorphology and laboratory analysis. We hypothesize that Spodosols with clay illuviation are locally found in the relatively level microrelief where organic matter is easily deposited associated with wetter moisture status. Active clay translocation occurs during the initial stage of soil development attributed to heavier rainfall. Therefore, clay coatings are the dominant pedofeatures in the lower parts of the pedons. Since coniferous trees were formed as the dense stand vegetation in the intermediate stage of soil development, organo-metallic complexes have progressively accumulated on the surface of illuvial clays or coagulated as spodic pellets in the subsurface horizons. During the advanced stage of soil development, clays mixed with organic-metallic complexes are slowly leached into the Bhs horizons within 50-cm depth, but the clays in suspension were easily leached to a deeper depth in this study area. Deforestation and fire events led to the removal and cleaning up of dense vegetation and litter in the study area nearly a century ago. Depodzolization and significant amounts of illuvial clay are thought to cause the lighter colors of subsurface horizons observed in this study. The soils derived from polypedogenic processes to form Ultisols and Spodosols are similar to the hybrid soils reported by Markewich and Pavich (1991). In the Jen-Lun forestry area, the coarser soil texture facilitated the leaching of organic matter from surface horizons into the B horizons and subsequent deposition in the lower parts of pedon JL-1. The other three pedons (JL-2 to JL-4) have fine soil textures and high extractable Fe and Al values. However, in these soils, only poorly oriented argillans occur in the Bh horizons. Wang and McKeague (1982) pointed out that translocation of clay complexed with organic matter, Al and Fe, might cause lack of well-oriented clay in spodic horizons despite occurrence of large amounts of illuviated clay in these horizons. Soil classification The seven pedons show intense accumulation of organic matter, Fe, Al, and clay in the Bh or Bhs horizons, and the subsurface horizons meet the criteria of both the spodic horizon and the argillic horizon as defined in Soil Taxonomy (Soil Survey Staff, 1999). Pedon JL-1 meets the criteria of morphology of Spodosols. The Bh horizons of the other three pedons with 7.5YR 4/6 color meet the proposed chemical criteria of

140 Spodosols and Ultisols in Subalpine Forest of Taiwan. Chen et al. EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7

Alo 0.5 Feo 0.5 % and ODOE value 0.25. Organic carbon content is more than 60 g/kg in a layer of 10 cm or more thick within the spodic horizons of pedons JL-1, JL-2 and JL-3. These pedons can be classified as Typic Haplohumods. However, organic carbon content in the spodic horizon of the other four pedons is less, so that they are Ultic Haplorthods. We propose that Argihumod and Argiorthod may be included in the Great Groups of Spodosols of Soil Taxonomy for those soils having the evidence of illuvial clay in or below the spodic horizon.

Table 1. The field soil morphology of seven pedons Horizon Depth(cm) Munsell color Structure # Consistence § Boundary¶

Pedon 901 (Fine, mixed, mesic, Ultic Haplorthod) Oi 28-0 2.5YR 2.5/2 Oe/A 0-5 5YR 2.5/1 2vf & fgr -- -- E 5-11 10YR 5/1 massive fir g Bhs 11-17 7.5YR 4/6 2f &m abk fir d Bt1 17-42 7.5YR 5/8 2f & m abk fri & fir d Bt2 42-67 7.5YR 5/8 2f & m abk fri & fir d Bt3 67-92 7.5YR 5/8 2f & m abk fir d C >92 10YR 5/6 2f&m abk fir --

Pedon 902 (Fine-loamy, mixed, mesic, Ultic Haplorthod) Oi 4-0 5YR 3/4 -- -- cs Oe/A 0-8 7.5YR 3/2 2vf & f gr fri cs Oa/A 8-14 5YR 2.5/1 2vf&f gr fri as E 14-18 7.5YR 6/1 massive fir as 7.5YR 5/8(mot) $ Bhs 18-30 7.5YR 5/6 2vf & f & m abk fir d Bt 30-46 7.5YR 5/6 2f & m abk fir as 2E 46-53 7.5YR 6/1 massive fir as 10YR 5/6(mot) 2BC 53-66 10YR 5/6 2f & m abk ss & sp --

Pedon 903 (Fine-loamy, mixed, mesic, Ultic Haplorthod) O 10-0 7.5YR 3/1 -- -- cs A 0-4 7.5YR 2.5/1 2vf & f gr fri as E 4-13 7.5YR 7/1 massive fir cw EB 13-30 7.5YR 7/1 massive fir d 10YR 5/8(mot) Bhs/Bt 30-44 7.5YR 4/3 2vf & f & m abk s & p d 7.5YR 5/6(8) BC 44-70 10YR 5/6 2vf & f & m abk fir d C >70 10YR 5/8 2f & m abk fir -

Spodosols and Ultisols in Subalpine Forest of Taiwan. Chen et al. 141 EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7

Table 1. (Continued) Horizon Depth(cm) Munsell color Structure # Consistence § Boundary¶ Pedon JL-1 (Fine-loamy, mixed, mesic, Ultic Haplohumod) O/A 0-16 5YR 3/2 2vf & f gr fri as E 16-22 10YR 6/4 or 2vf & f abk fri as 10YR 6/3 Bh1 22-28 5YR 3/4 or 2vf & fgr, 2vf & f abk fm cs 5YR 4/4 Bh2 28-34 5YR 4/6 2vf & f abk fm cs 7.5YR 4/4 or 7.5YR 4/6 (mot) Bw1 34-50 10YR 5/6 2fgr, 2vf & f abk fm & ss & sp g Bw2 50-73 10YR 5/4 2fgr, 2vf & f abk fm & ss & sp d Bw3 73-95 7.5YR 6/8 2fgr, 2vf & f abk fm & ss & sp as C >95

Pedon JL-2 (Fine-silty, mixed, mesic, Ultic Haplohumod) O/A 0-17 5YR 2/1 2vf & f gr fri as E 17-20 5YR 6/1 massive fm as 10YR 7/6 (mot)$ Bh1 20-32 7.5YR 4/6(80%) 2vf & fgr, 1vf & f & m abk fm g 5YR 3/3(20%) Bh2 32-44 7.5YR 4/6(70%) 2vf & fgr, 1f & m abk fm d 5YR 3/3(30%) Bw 44-62 7.5YR 5/8 2vf & fgr, 2f & m abk fm cs 2E 62-70 10YR 7/4 2fgr, 2f & m abk fm, ss, & sp cs 2Bw 70-83 5YR 5/8 2vf & fgr, 1vf & f & m abk fm g 3BC1 83-107 10YR 6/8 2fgr, 1f & m abk fm g 3BC2 107-120 10YR 4/3 2vf & f gr, 2vf & f abk fm d 3C 120-150 7.5YR 3/2 2vf & f abk fm as

Pedon JL-3 (Fine-silty, mixed, mesic, Ultic Haplohumod) O/A 0-9 10YR 3/3 2vf & f gr fri cs Bw 9-21 10YR 7/6 1vf sbk, 2vf & f gr ss aw 2A 21-26 10YR 4/1 2vf & f gr fri aw 2E 26-46 2.5Y 8/0 massive s & p as 10YR 7/8(mot) 2Bh1 46-55 7.5YR 4/6(70%) 2vf & f gr, 1vf & f abk fm g 7.5YR 3/4(30%) 2Bh2 55-72 7.5YR 3/4 2vf & f gr, 2vf abk fm as 2C 72-100 2.5YR 6/4 -- -- g

Pedon JL-4 (Fine, mixed, mesic, Ultic Haplorthod) O/A 0-3 10YR 5/2 2vf & gr fri cs E 3-20 10YR 7/2 & massive ss & sp as 10YR 6/6 Bh 20-32 7.5YR 4/6 2vf & f gr, 1vf abk fm, ss & sp d Bw 32-50 7.5YR 5/8 2vf & f gr, 1vf & f abk fm, ss & sp g 2Bw 50-70 7.5YR 5/8 1f & m abk ss & sp g 2C 70-90 10YR 6/8 1f abk fm a $ (mot)=mottles. # 1=strong, 2=moderate, vf=very fine, f=fine, m=medium, gr=granular, abk=angular blocky, sbk=subangular blocky. § fri=friable, fm= firm, sf=slightly firm, s=sticky, p=plastic, ss=slightly sticky, sp=slightly plastic. ¶ a= abrupt, s=smooth, g=gradual, w=wave, c=clear, d=diffuse.

142 Spodosols and Ultisols in Subalpine Forest of Taiwan. Chen et al. EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7

Table 2. The physical and chemical properties of selected horizons in seven pedons

Texture DCB Oxalate Pyrophosphate

Horizon Sand Silt Clay pH OC CEC# BS¶ Fed Ald Feo Alo Fep Alp ODOE ------g/kg ------g/kg cmol(+)/kg % ------g/kg ------Pedon 901 Oi - § - - 3.5 374 76.4 1 ------0.77 E 568 204 228 3.7 18 21.3 3 42.8 2.1 9.1 2.2 6.5 1.8 1.43 Bhs 491 184 325 4.2 32 30.5 2 60.2 19.6 16.9 6.1 33.4 7.0 3.03 Bt1 395 188 417 4.8 23 22.1 2 62.5 24.7 17.4 8.6 23.7 9.4 2.00 Bt2 390 166 443 4.9 23 13.0 3 66.1 15.8 11.9 6.0 13.0 6.5 2.01 C 598 230 172 4.9 12 7.0 6 44.3 3.8 3.1 2.3 0.8 1.4 0.13 Pedon 902 Oe/A 428 310 262 4.0 145 38.7 2 32.6 2.2 6.2 9.0 7.1 11.1 2.19 E 560 246 194 4.0 15 11.8 6 37.6 1.3 8.4 8.6 5.5 11.0 0.57 Bhs 490 266 244 4.4 22 15.8 4 59.2 4.6 17.7 11.1 19.9 15.4 1.48 Bt 478 199 324 4.6 18 12.0 5 42.2 4.1 10.2 11.5 18.2 16.0 1.17 2E 515 307 178 4.7 3 13.7 4 18.5 0.7 1.7 9.0 0.8 10.2 0.08 Pedon 903 O - - - 4.4 82 19.7 10 ------0.66 A 604 254 142 3.9 31 14.3 10 18.8 0.9 3.0 8.3 2.2 10.3 0.62 E 635 240 126 4.4 8 14.1 9 18.4 0.4 1.1 8.0 0.4 10.0 0.20 EB 574 254 171 4.5 10 17.0 7 33.3 0.9 3.0 8.7 3.9 10.7 0.11 Bhs/Bt 491 230 279 4.3 26 25.6 6 61.2 12.9 18.7 13.7 25.3 19.3 2.35 BC 454 266 280 4.5 22 19.1 7 72.5 7.2 17.3 14.8 20.1 20.4 1.13 Pedon JL-1 O/A 183 535 282 4.0 - 65 2 9.9 2.3 4.6 2.6 2.9 2.2 0.49 E 229 426 345 3.7 46 16 2 14.0 1.7 5.3 1.6 5.0 1.4 0.24 Bh2 249 377 374 4.1 59 29 1 28.0 8.0 13.7 8.7 17.2 8.7 1.31 Bw1 261 371 368 4.4 52 24 1 24.1 9.3 16.1 10.3 16.8 10.3 0.90 Pedon JL-2 O/A 340 515 145 3.9 - 59 1 12.5 4.7 9.1 4.5 8.5 4.6 0.39 E 282 600 118 3.8 55 26 4 20.4 3.4 14.2 4.3 11.0 3.4 0.90 Bh1 335 557 108 4.2 80 42 2 48.6 12.8 36.4 10.5 33.6 12.3 2.34 Bw 315 523 162 4.5 68 35 2 46.8 14.4 36.5 12.7 35.4 14.7 1.88 2E 380 562 58 4.5 35 33 1 34.3 10.2 23.2 8.5 26.6 10.3 1.10 2Bw 359 462 179 4.7 48 27 2 54.3 18.3 45.8 14.1 39.5 16.0 1.29 Pedon JL-3 O/A 187 437 376 4.0 83 22 4 19.3 5.8 8.7 4.2 8.4 4.4 0.65 Bw 301 575 124 3.8 59 30 1 43.3 5.0 27.3 4.4 23.4 4.1 1.34 2E 273 590 137 3.7 17 19 2 20.4 2.5 8.8 2.2 9.2 1.8 0.31 2Bh1 383 513 104 4.1 60 35 1 70.2 11.2 38.1 8.6 42.0 10.3 1.88 Pedon JL-4 O/A 178 757 65 3.5 102 31 2 14.8 3.0 5.5 2.4 7.1 2.4 0.72 E 253 679 68 3.7 16 15 2 11.6 2.0 3.2 1.6 4.8 1.5 0.16 Bh 584 382 34 4.4 44 29 3 81.8 19.5 26.9 9.0 47.9 15.7 0.98 Bw 469 492 39 4.7 17 14 2 54.3 15.2 21.7 7.9 32.7 12.8 0.59 2Bw 419 449 132 4.9 10 10 6 42.7 11.4 17.4 6.0 22.4 8.6 0.41 # : cation-exchange capacity; ¶ : base saturation; §: No data.

Spodosols and Ultisols in Subalpine Forest of Taiwan. Chen et al. 143 EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7

Figure 1. Photomicrographs of the thin sections of selected pedons, plane polarized light: (a) isotropic dark aggregates composed of irregular organo-metallic complexes on the pedsurface and coarse grain in Bhs horizon of pedon 901. Scale of bar is 1 mm, OM= organ-metallic complex, C=coarse grain; (b) poorly-oriented clay coatings and pellet-like aggregates on the pedsurface in Bt1 horizon of Pedon 901. Scale of bar is 1 mm, CC= clay coating, P= pellet; (c) isotropic dark pellets infilled in the void and coated on the sand grain in Bhs horizon of pedon 902. Scale of bar is 2 mm, V= void, P= pellet; (d) well-oriented clay coatings along root channel in Bt horizon of pedon 902. Scale of bar is 2 mm, CC= clay coating, R= root channel; (e) organo-metallic complexes shown as dark smaller pellets in the void and larger aggregates on the pedsurface in Bhs horizon of pedon 903. Scale of bar is 1 mm, V= void, OM= organo- metallic complex; (f) hypocoatings of clay in the wall of vugh and few organo-metallic complexes on the pedsurface in Bhs horizon of pedon 903. Scale of bar is 1 mm, HC=hypocoating, OM= organo-metallic complex.

144 Spodosols and Ultisols in Subalpine Forest of Taiwan. Chen et al. EUROPEAN SOIL BUREAU  RESEARCH REPORT NO. 7

Conclusions In the present study, the soil colors are marginal to 7.5YR 5/6 in all the subsurface horizons with various degrees of spodic material accumulation despite the fact that all the chemical properties in the Bt horizons satisfied the criteria of spodic horizon. Clay illuviation is not only the major pedogenic process, but also occurred earlier rather than podzolization. Illuvial clays associated with organo-metallic complexes were translocated and large amounts of them were deposited in the upper part of subsurface horizons, particularly within 50-cm depth; however, some of the illuvial clays were leached to a deeper depth. We conclude that coniferous vegetation and relatively high rainfall strongly influence the pedogenic processes of the transitional soils between f Ultisols and Spodosols in Taiwan. Deforestation reduced the rate of podzolization, but a large amount of rainfall (>4000 mm/yr) accelerated the clay translocation and spodic material illuviation. Spodosols are only found on some flat areas with depressional microrelief of mountain areas of Taiwan where litter easily accumulates to produce large amounts of organic substances that may form the organo-metallic complexes. References Bockheim, J. G., J. G. Marshall, and H. M. Kelsey. 1996. Soil-forming processes and rates on uplifted marine terrace in southwestern Oregon, USA. Geoderma 73:39-62. Bullock, P. and B. Clayden. 1980. The morphological properties of Spodosols. p. 45-65. In B. K. G. Theng (ed.) Soils with variable charge. New Zealand Society of Soil Science Soils Bureau, Department of Science and Industrial Research, Lower Hutt, New Zealand. Bullock, P., N. Fedoroff, A. Jongerius, G. Stoops, and T. Tursina. 1985. Handbook for thin section description. Waine Res. Publ., Albrighton, England. 152p. Chen, Z. S., J. C. Liu, and H. C. Chiang. 1995. Soil properties, clay mineralogy, and genesis of some alpine forest soils in Ho-Huan Mountain area of Taiwan. J. Chinese Agric. Chem. Soc. 33:1-17. Daly, B. K. 1982. Identification of podzols and podzolized soils in New Zealand by relative absorbance of oxalate extracts of A and B horizons. Geoderma 28: 29-38. Harris, W. G., and K. A. Hollien. 1999. Changes in quantity and composition of crystalline clay across E- Bh boundaries of Alaquods. Soil Sci. 164:602-608. Hseu, Z. Y., Z. S. Chen, and Z. D. Wu. 1999. Characterization of placic horizons in two subalpine forest Inceptisols. Soil Sci. Soc. Am. J. 63:941-947. Li, S. Y., Z. S. Chen, and J. C. Liu. 1998. Subalpine loamy Spodosols in Taiwan: characteristics, micromorphology, and genesis. Soil Sci. Soc. Am. J. 62:710-716. Loveland, P. J. and P. Digby. 1984. The extraction of Fe and Al by 0.1 M pyrophospate solutions: a comparion of some techniques. J. Soil Sci. 35: 243-250. Lundstrom, U. S., N van Breemen, and D. Bain. 2000. The podzolization processes: A review. Geoderma 94:91-108. Markewich, H. W., and M. J. Pavich. 1991. Soil chronosequence studies in temperate to subtropical, low- latitude, low-relief terrain with data from the eastern United States. Geoderma 51:213-239. McKeague, J. A., and J. H. Day. 1966. Dithionite and oxalate extractable Fe and Al as aids in differentiating various classes of soils. Can. J. Soil Sci. 46:13-22. Mehra, O. P., and M. L. Jackson. 1960. Iron oxides removed from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate. Clays Clay Minerals 7: 317-327. Soil Survey Staff. 1999. Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys. USDA-NRCS, Agricultural Handbook No. 436, 2nd ed., U.S. Gov. Print. Office, Washington, D.C. 869pp. Wang, C., and J. A. McKeague. 1982. Illuviated clay in sandy podzolic soils of New Brunswick. Can. J. Soil Sci. 62: 79-89.

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