Comparing surface erosion processes in four soils from the Loess Plateau under extreme rainfall events

This research aims to improve erosion control practice in the Loess Plateau,by studying the surface erosion processes,including splash,sheet/interrill and rill erosion in four contrasting soils under high rainfall intensity(120 mm h^(−1))with three-scale indoor artificial experiments.Four contrasting soils as sandy loam,sandy clay loam,clay loam and loamy clay were collected from different parts of the Loess Plateau.The results showed that sediment load was significantly impacted by soil properties in all three sub-processes.Splash rate(4.0-21.6 g m^(−2∙)min^(−1))was highest in sandy loam from the north part of the Loess Plateau and showed a negative power relation with the mean weight diameter of aggregates after 20 min of rainfall duration.The average sediment load by sheet/interrill erosion(6.94-42.86 g m^(−2∙)min^(−1))was highest in clay loam from middle part of the Loess Plateau,and the stable sediment load after 20 min showed a positive power relation with the silt content in soil.The average sediment load increased dramatically by rill and interrill erosion(21.03-432.16 g m^(−2∙)min^(−1)),which was highest in loamy clay from south part of the Loess Plateau.The average sediment load after the occurrence of rill showed a positive power relation with clay content and a negative power relation with soil organic matter content.The impacts of slope gradient on the runoff rate and sediment load also changed with soil properties.The critical factors varied for different processes,which were the aggregate size for splash erosion,the content of silt particles and slope gradient for sheet/interrill erosion,and the content of clay particles,soil organic matter and slope gradient for rill erosion.Based on the results of the experiments,specific erosion control practices were proposed by targeting certain erosion processes in areas with different soil texture and different distribution of slope gradient.The findings from this study should support the improvement of erosion prediction and cropland management in different regions of the Loess Plateau.

Soil Erosion Characteristics According to Tree-rings in a Karst Area

Dendrogeomorphological method was used to study soil erosion in two typical karst sites （Puding and Zhengfeng） in Guizhou Province, China. Eleven pairs of exposed and unexposed tree roots were measured in the field and sampled for anatomical characteristics. The results showed that the exposed roots recorded karst soil erosion. Significant changes were shown in the anatomical characteristics of the exposed tree roots when soil erosion occurred, such as suddenly narrower tree rings, smaller cells, and fewer earlywood cells. Meanwhile, the fabre lumen and vessel lumen areas markedly declined to the range of 39.20% to 70.66%, which only slightly implies soil erosion. The accurate time period during which soil erosion occurred was identified and combined with the age of the tree roots. Dynamics of soil erosion were calculated and soil erosion recorded by the exposed roots from 2002 to 2007 at an average rate of 0.484 t y^-1 at Puding, and from 2005 to 2007 at an average rate of 0.051 t y^-1 at Zhenfeng. Karst soil erosion was recorded by not only one species but by multi species of broadleaf tree roots, which can significantly enhance the study of karst soil erosion through the use of Dendrogeomorphological method. The quantity of eroded soil was found to be extremely large when records from the exposed tree roots were compared with estimates from site measurements of runoff. The major type of karst soil erosion was underground soil loss and this comprised approximately 2/3 of total erosion.