RELATIONS OF SOIL PROPERTIES TO TOPOGRAPHY AND VEGETATION IN A SUBTROPICAL RAIN-FOREST IN SOUTHERN TAIWAN

Soil chemical properties for a subtropical rain forest in the Nanjensh an Reserve, southern Taiwan, were examined to determine soil-landscape and soil-vegetation relationships. Soil sampling sites were separated into four groups based on landscape features and exposure to the prev ailing northeasterly monsoon winds. Corresponding vegetation types wer e delimited along the first DCA axis. The forest showed a drastic chan ge both in structure and floristic composition along the wind-stress g radient. Redundancy analysis (RDA) showed that both topographic variab les and vegetation types were needed to explain the variation in soil data. Soil properties that differed significantly among landforms were pH: available N, CEC, exchangeable Al, K, Ca and Mg. Levels of pH, ex changeable Ca and Mg increased in a downslope direction, and exchangea ble Al tended to be higher in the upper slope soils. These trends poin ted to the importance of slope processes in redistribution of soil min erals. The main differences in soil properties attributed to the influ ence of the occupying vegetation were apparently aspect dependent. The contents of available N, exchangeable K, and CEC in the 0-40 cm depth of soils under windward low-stature (mostly sclerophyllous) forest we re consistently lower compared to those under the leeward forest. For a given catena, however, soil variability associated with vegetation d ifferences seemed to be confounded by the slope processes.