Positive and negative terrains on northern Shaanxi Loess Plateau

The Loess positive and negative terrains (P–N terrains), which are widely distributed on the Loess Plateau, are discussed for the first time by introducing its characteristic, demarcation as well as extraction method from high-resolution Digital Elevation Models. Using 5 m-resolution DEMs as original test data, P–N terrains of 48 geomorphological units in different parts of Shaanxi Loess Plateau are extracted accurately. Then six indicators for depicting the geomorphologic landscape and spatial configuration characteristic of P–N terrains are proposed. The spatial distribution rules of these indicators and the relationship between the P–N terrains and Loess relief are discussed for further understanding of Loess landforms. Finally, with the integration of P–N terrains and traditional terrain indices, a series of un-supervised classification methods are applied to make a proper landform classification in northern Shaanxi. Results show that P–N terrains are an effect clue to reveal energy and substance distribution rules on the Loess Plateau. A continuous change of P–N terrains from south to north in Shaanxi Loess Plateau shows an obvious spatial difference of Loess landforms and the positive terrain area only accounted for 60.5% in this region. The P–N terrains participant landform classification method increases validity of the result, especially in the Loess tableland, Loess tableland-ridge and the Loess low-hill area. This research is significant on the study of Loess landforms with the Digital Terrains Analysis methods.