Genesis of Soils along a Toposequence in Nanjenshan Long-Term Ecological Research Site, Taiwan

Abstract

The influence of topography on soil development, classification and the distribution of soil properties are poorly understood in Taiwan. The influence of landscape morphology on soil profile development is important in understanding the processes responsible for weathering, leaching, and redistribution of nutrients and other dissolved solutes within forested landscape. Our objectives, therefore, were to examine the genesis of soil along a toposequence in Nanjenshan and to determine the effect of topographic position on soil development and classification. The study site is a one-hectare, altitudinal transect, established on the northwestern ridge of Nanjenshan, the north part of the Nanjenshan Long-Term Ecological Research Site in southern Taiwan. Results indicate that strong correspondences were found between the landscape morphology, distribution of soil properties, soil genesis, and soil classification in this study area. Soils ranged from a Typic Paleudults in the summit position, through a Typic Dystrudepts in lower backslope position, and finally a Typic Dystrudepts in footslope position; this is considerable variability within a horizontal distance of 500 m. The distribution of soil properties varied with soil genesis and was strongly related to landscape position. In general, sand, silt, organic carbon, exchangeable bases (K, Na, Ca, and Mg), and base saturation (%) increased downslope, while solum thickness, clay, bulk density, and pH (H2O) generally decreased downslope. Monsoon winds and typhoon both have impacts on the ecosystem and forest physiognomy of this study area. Additional research is needed to more fully understand the interactive relationships among landscape position, soil properties, and vegetal composition.