Positive and negative terrains on northern Shaanxi Loess Plateau

Abstract

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.

Ecosystem Services and Ecological Restoration in the Northern Shaanxi Loess Plateau, China, in Relation to Climate Fluctuation and Investments in Natural Capital

“…High in the west and becoming lower in the east, the NSLP is a hilly, gullied area of the Loess Plateau [29,30]. The Mu Us desert in the northwest of Yulin has a primarily psammophyte vegetation type.…”

“…Crops are mainly corn, soybeans and wheat, and the grassland is dominated by Miscanthus grass and clover [29]. This area has a semi-arid continental monsoon climate [30] and is characterized by warm and rainy summers and cold and dry winters [31]. (Table 1), it can be seen that 694 km 2 and 556 km 2 of croplands in 2000 have been replaced by woodlands (including scrublands) and grasslands, respectively, due to the GFG project.…”

Point Cloud Oriented Shoulder Line Extraction in Loess Hilly Area

“…Figure.1 illustrates a hypothetical profile representing the point of morphological variation between the inner-gully area (AC) and the inter-gully (BC) between the loess positive and negative terrains (P-N terrains) (Zhou, Tang et al 2010). The tool of RiScan software have been used to remove "noise" points with point cloud data of this area.…”

“…(Yan, Tang et al 2014) Therefore, the shoulder line should be extracted to separate surface into positive terrain and negative terrain and removing "noise" points respectively. Many methods of shoulder line extraction have been proposed based on DEM, which can be referenced (Lu, Qian et al 1998, Xiao and Tang 2007, Zhou, Tang et al 2010, Zhang, Tang et al 2012, Yan, Tang et al 2014. However, the method of high precise shoulder line extraction based on point cloud data is still unsolved because of the "noise" points.…”

Transitional relation exploration for typical loess geomorphologic types based on slope spectrum characteristics

“…In previous studies, loess geomorphology has been classified and characterized by using the slope spectrum index (Li et al, 2007;Wang et al, 2008;Zhou et al, 2010). The achievement of 1 : 1 000 000 scales in the Chinese Geomorphologic Database (CGD) provides the distribution of the loess geomorphologic types (Cheng et al, 2011a).…”