Soil Characteristics and Genesis Processes of a Subtropical Low-Elevation Mountain Forest in Central Taiwan

Two representative soil pedons under natural broadleaf stands in the Lienhuachih Experiment Forest in central Taiwan were selected to investigate their soil characteristics and evaluate soil genesis processes. The studied soils were acidic (pH 3.80~4.92) with low organic carbon contents (< 4%) and extremely low base saturation (< 5%), which correspond to forest soils in tropical and subtropical regions. Brunification and laterization were found in forest soils where well crystalline iron and aluminum contents are relatively high (> 50%). There was an illuviation phenomenon of clay and free Fe and Al oxides (Fed and Ald) in the studied soils, whereas amorphous Fe and Al oxides (Feo and Alo) and organic Fe and Al complexes (Fep and Alp) were predominant forms in the surface soils of this forest due to effects of the soil organic matter. Well-developed soils were found at the footslope site owing to higher contents of well crystalline Fe and Al oxides compared to those at the backslope site. Soils at the footslope site with bisequences were classified as Typic Hapludults, and those at the backslope site were classified as Typic Dystrudepts. We concluded that the soils have undergone strong weathering under paleoclimatic conditions. These soils had been disturbed in the past and had gone in new genesis directions due to erosion and colluvial conditions resulting from the unstable topography and frequent tectonic episodes.