Soil characteristics and variability of an Ultisol toposequence in Nanjenshan subtropical forest ecosystem of Taiwan
2001
Tsai, C.C. | Chen, Z.S.
The effect of topography on the soil properties under a forest ecosystem is complicated, particularly in subtropical regions. The soil characteristics along a toposequence in subtropical forest soil have seldom been investigated in Taiwan. This study describes the soil characteristics and discusses the variability of an Ultisol toposequence in Nanjenshan region of Kenting National Park of southern Taiwan. The Ultisols are derived from a residuum of sandstone and shale. Investigated were the soils selected from the summit, the upper backslope, and the lower backslope landscape positions. The soil morphological characteristics of the selected representative soil pedon in different landscape positions closely resemble each other. It is suggested, based on the higher coarse sand contents in the surface soil of the summit soil, that these sand particles are carried by the northeastern monsoon from the seashore and deposited on the summit. It is also suggested that for the changes in total sand and total clay content from the A horizon to the Bt horizon of the soil pedon, the sand weathering in the surface soil and intensive clay illuviation in the Bt horizon are the predominant pedogenic processes of this Ultisol toposequence. In addition, the depth distribution of DCB-extractable Fe correlates with the clay distribution in three landscape positions. Moreover, the slope gradient is proposed to affect the different distributions of soil properties along this toposequence. The substantial weathering and pedogenic processes, which occur in argillic horizons, lead to a lower variability of soil properties at the Bt horizon than that of surface horizon.
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