Monday, November 13, 2006

Soil Characteristics and Pedogenesis of Sandy and Loamy Spodosols of the Chushan Region in the Alishan Area of Central Taiwan.

Chun-mei Chiu, UW-Madison, Dept of Soil Science, 1525 Observatory Dr, Madison, WI 53706-1299, Zueng Chen, National Taiwan University, Dept. of Agric. Chemistry National Taiwan Univ., #1 Sect. 4th, Roosevelt Road, Taipei, 106-17, TAIWAN, and Cynthia Stiles, Dept of Soil Science, 1525 Observatory Dr, Madison, WI 53706-1299.

Spodosols occurred mainly in cool humid climates under coniferous forest vegetation in coarse textured parent material. Spodosols have been studied intensively in Taiwan. However, there is still uncertainty about dominant processes that form these Spodosols, especially with fine soil texture. The objectives of this study are to elucidate the genesis of podzolization and clay illuviation in sandy and loamy Spodosols formed in Taiwan. Five representative pedons of subalpine Spodosols were selected for study. The study area is located in southern Taiwan on gentle slopes (<5%) of mixed sandstone and shale at elevations >2300 m, covered by coniferous vegetation. Soil texture of Spodic horizon in studied soils includes loamy sand, sandy loam, and sandy clay loam. These soils are characterized by strong acidity and low base saturation. Higher organic carbon, extractable iron, and clay particle are significantly accumulated in the spodic horizon than overlying albic horizons. These results indicated the dominant illuviation process of organo-metallic complex and fine clay particles. Micromorphological examination also indicated the dark pellets of organs and argillans were translocated into the soil pores, organs or organo-ferrans were formed in voids or aggregate surfaces, groundmass was formed in spodic horizons. These results indicated that organic carbon, Fe, and clay were all illuviated into the spodic horizons. In this study, podzolization and clay illuviation are the primary pedogenic processes for both sandy and loamy Spodosols. Pedons with sandy texture tend to have significant higher organic carbon and organo-Fe contents in the Spodic horizon and also a slight higher clay contents in spodic horizons. Pedons with loamy texture tend to have pedogenic processes including podzolization and clay illuviation in the profile due to inherent differences in water movement.