Gully Erosion Regionalization of Black Soil Area in Northeastern China

Gully erosion is the frequent and main form of soil erosion in the black soil area of the northeastern China, which is one of the most important commodity grain production bases in China. It is encroaching upon the fertile farmland there. Regionalization of gully erosion can reveal the spatial distribution and regularity of the development of gully erosion. Based on the eco-geographical regional background features of the black soil area, this study combined the regionalization with influencing factors of the development of gully erosion. GIS spatial analysis, geostatistical analysis, spatial statistics, reclassification, debris polygon processing and map algebra methods were employed. As a result, the black soil area was divided into 12 subregions. The field survey data on type, length, volume and other characteristics indicators of gully erosion were used to calibrate the results. Then the features of every subregion, such as where the gully erosion is, how serious it is, and why it happens and develops, were expounded. The result is not only an essential prerequisite for gully erosion surveys and monitoring, but also an important basis for gully erosion prevention.

Gully Impact on Soil Moisture in the Gully Bank

In order to preliminarily look at rules for soil moisture changes in the bank of the gully and to provide some recommendations for vegetative restoration in gully bank regions in the Loess Plateau, changes of soil moisture with depth and distance to the gully edge and their dynamic changes with time were observed to study the soil water characteristics in the bank of the gully. The results showed that soil water content increased with increasing distance from the gully edge, whereas for the same time period, the closer the distance to the gully wall, the greater the water loss; and that the influential distance of side evaporation decreased as depth increased.

Spatial distribution and influencing factors of Surface Nibble Degree index in the severe gully erosion region of China’s Loess Plateau

In China’s Loess Plateau severe gully erosion(LPGE)region,the shoulder-line is the most intuitive and unique manifestation of the loess landform,which divides a landform into positive and negative terrains(PNTs).The spatial combination model of PNTs is of great significance for revealing the evolution of the loess landform.This study modeled and proposed the Surface Nibble Degree(SND),which is a new index that reflects the comparison of the areas of PNTs.Based on 5 m DEMs and matched high-resolution remote sensing images,the PNTs of 164 complete watersheds in the LPGE were extracted accurately,and the SND index was calculated.The spatial distribution trend of SND was discussed,and the relationship between SND and the factors that affect the evolution mechanism of regional landform was explored further.Results show that:(1)The SND can be calculated formally.It can quantify the development of the loess landform well.(2)The SND of the LPGE has evident spatial differentiation that increases from southwest to northeast.High values appear in Shenmu of Shaanxi,Shilou of Shanxi,and northern Yanhe River,whereas the low values are mainly distributed in the southern loess tableland and the inclined elongated ridge area of Pingliang in Gansu and Guyuan in Ningxia.(3)In the Wuding River and Yanhe River,the SND decreases with the increase in flow length(FL).In the North-Luohe River and Jinghe River,the SND increases with FL.(4)SND is significantly correlated with gully density and sediment modulus and moderately correlated with hypsometric integral.As for the mechanism factors analysis,the relationship between loess thickness and SND is not obvious,but SND increased first and then decreased with the increase of precipitation and vegetation in each geographical division,and we found that the land use type of low coverage grassland has greater erosion potential.