Relationships between soil properties and slope position in a lowland rain forest of southern Taiwan

The aspect and slope can control the movement of water and material in a hillslope and contribute to the spatial differences of soil properties. In a forest ecosystem, soil properties are also influenced by vegetation composition. The objectives of this study are to examine the characteristics and spatial differences of soil properties in a lowland evergreen broad-leaved rain forest in southern Taiwan, and to clarify the relationships between soil properties and the landscape. A total of 565 soil samples were taken at 0-5 and 5-15 cm in 74 contiguous 10 x 10-m quadrates along an altitudinal transect ranging from 300 to 480 m. The study transect was divided in three slope positions: summit, backslope and footslope positions, each with a different floristic composition and structure. Our study showed that organic carbon, available N, available K, extractable Fe and exchangeable Na were highest on the summit, while pH, available P, exchangeable Ca and Mg were significantly higher on the footslope at 0-5-cm soils. Similar patterns were observed at subsurface 5-15-cm depth soils. The OC increased with increasing altitude, probably due to the quality of litterfall and lower rate of decomposition in the summit forest. The results of redundancy analysis (RDA) also revealed clear separation of soil properties among slope positions. These results confirmed that slope factor involved in the transport and accumulation of solutes resulted in higher pH, exchangeable Ca and Mg, lower organic carbon, available N and K, extractable Zn in the depositional areas of footslope. Although the soil properties associated with landscape have been better understood, further studies are required to clarify the relationships between soil nutrient status and plants in Taiwan. (C) 2004 Elsevier B.V. All rights reserved.