Dynamic monitoring of soil bulk density and infiltration rate during coal mining in sandy land with different vegetation

To investigate the effects of coal mining on soil physical properties,sandy lands with three major vegetation types(Salix psammophila,Populus simonii,and Artemisia ordosica)were investigated by the ring knife method and double-ring infiltrometer.Specifically,variations in soil bulk density and water infiltration rate and the influences of coal mining and vegetation type on the properties during different subsidence stages were studied at the Shendong Bulianta mine.The results showed that,in the period before mining,soil bulk density occurred in the order A.ordosica>P.simonii>S.psammophila,with a negative correlation between the initial infiltration rate and steady infiltration rate being observed.In the period during mining and 3 months after mining,there were no significant differences in soil bulk density and water infiltration rate among vegetation types.At 1 year after mining,the soil bulk density occurred in the order A.ordosica>S.psammophila>P.simonii,having a negative correlation with the steady infiltration rate.The water infiltration depths of the S.psammophila,P.simonii and A.ordosica were 50,60,and 30 cm,respectively.The infiltration characters were simulated by the Kostiakov equations,and the simulated and experimental results were consistent.Linear regression revealed that vegetation types and soil bulk density had significant effects on soil initial infiltration rate during the four study periods,and the infiltration rate of the period 1 year after mining was mainly influenced by the soil bulk density of the period before mining.The results indicated that vegetation types had significant effects on soil bulk density,and that the tree-shrub-grass mode was better than one single plantation for water conversation and vegetation recovery in sandy land subjected to mining.

Spatial distribution of Agriophyllum squarrosum Moq. (Chenopodiaceae) in the straw checkerboards at a revegetated land of the Tengger Desert, northern China

The present study focuses on straw checkerboards established in the Shapotou Desert Research and Experimental Station at the southeastern edge of the Tengger Desert and their effects on the species richness and the abundance of Agriophyllum squarrosu Moq. Specifically, detailed analyses on the spatial distribution of A. squarrosum and the related soil properties were carried out at a small scale in the straw checkerboards. A. squarrosum is an excellent pioneer plant for revegetation in desert areas. However, the distribution pattern of A. squarrosum and the influencing factors have not been sufficiently delineated. The results showed that the species richness and the abundance of A. squarrosum were decreased exponentially from the border to the center of the straw checkerboards. At the micro-geomorphological scale, the soil texture, soil organic matter （SOM）, soil nutrients （nitrogen, phosphorus and potassium）, and soil infiltration rate in the topsoil tended to increase from the center to the border within a straw checkerboard, while soil moisture presented an opposite tendency. The soil seed bank ofA. squarrosum, soil bulk density, electrical conductivity, sand content, CaCO3 accumulation, and pH showed no significant difference （P〉0.05） between the border and the center of the straw checkerboards. Multiple linear regression analysis indicated that the abundance of A. squarrosum was mainly determined by the concentrations of SOM, nitrogen, and the infiltration rate, implying that nutrient acclimation was the optimal competitive strategy ofA. squarrosum for surviving in a barren natural environment of an arid desert region.