Research On Soil Structure And Water Transport In North Rocky Mountain

Soil structure plays an important role in runoff, water transport in soil, water storage capacity and conversation capacity. Soil structure can have an effect on the generation of water and soil loss and water storage in deep soil, so it affect forest hydrology significantly. In this paper, JiFeng, north typical rocky mountain was chosen as a site where six plots were selected to analyze soil structure and macropore ridius, density by using cutting rings for stratified sampling. Soil water infiltration, water characters and water seasonal variation were analyzed by water breakthrough curves, centrifugation and oven drying method. At the same time, the relation between water infiltration and soil macropores and water infiltration models were established. The results were as follows:(1) In the experimental plots, small stones(radius>2mm) were the most numerous in the plot1, plot2, plot5and plot6with a value of more than10%. There were less stones in the plot3and plot4. For most soil layers, the value of stones was less than1%. Sand was the main constituents of soil composition of grain diameter with a maximum of73.16%. The volume content if small stone in the plots varied from4.546%to10.563%. There was less difference in the volume content of the same soil layer in differen plots and the spatial variation value was about0.2. The soil density in the former three layers was basically identical, so was the density in the latter two layers in the plotl and plot2. Soil density was the same thing in the former two layers, so was the density in the latter three layers in the plot3, plot5and plot6. The soil density increased with soil layer increase in the plot4. There was an inverse relation between soil density and soil porosity. The fractal dimension of soil aggregates, R0.25, MWD and GMD did not show some regularity. In terms of the overall trend, there was a better stability in the lower soil layers. In JiuFeng, MWD and GMD can evaluate soil exactly than soil aggregates and R0.25.(2) radii of soil macropores mainly ranged from0.1mm to0.4mm and they accounted for97%of the total macropore numbers. There were less macropores with its raius changing from0.4mm to0.6mm. There was no significant difference in the radii of soil macropores in all plots and the radius focused on0.17mm.(3) Due to the effect of plot3, there was a negative relation between gravel volume content and nacropore radius, but the correlation coefficient was lower. When the plot3was removed, there was a positive relation between gravel volume content and macropore radius with the correlation coefficient being0.4808. There was no relation between macroporedensity and gravel content. When the gravel content was larger than6%, in a plot, gravel content presented a positive relation with macropore radius. While the gravel content was less than4.55%, a inverse relation can be obtained. The relation between macropore density and gravel content was positive or negative.(4) In plot I and plot2, the water infiltration curves approached to each other in the former three soil layers and curves were close to each other in the latter two layers. The water infiltration rate was larger in the latter soil layers. From plot4to plot6. there was a similar regulation in water infiltration which showed that water infiltration curves approached to each other in the former two soil layers and curves were close to each other in the latter three layers. The water infiltration rate was larger in the former two soil layers. The change rule of steady infiltration coefficient and the change law of accumulated infiltration volume were similar to the steady infiltration rate. Horton model and universal empirical model can be used to stimulate water infiltration rate. Horton model had a better stimulation effect.(5) The shapes of water retention curves were parallel and there was little difference in the water character curves. The water character curves in the low soil layers exceeded those in upper soil layers. The demarcation point of water suction was0.1MPa. The realation between water content and water suction obeyed empirical equation0=AS-B. The water-holding ability was analyzed by specific water capacity equation(C(?)=ABS-(B+I)). The equation (0-AS-B) evaluated water-holding ability better. The point of water suction demarcation between soil available water and water that is difficult to contain was0.3MPa.(6) Soil water content changed during a year in the plots. In the plot I and plot2, water content reached a maximum on11th September and water content from mid-July to September was larger than that from October to December. In the plot3, plot4, plot5and plot6, water content decreased with time increase. There was no regularity in the change of water content in soil layers during a year and the difference of average water contents in soil layers was not significant.(7) The dye staining depth was10cm in two plots and water infiltration rates in the upper soil were less than those in the lower soil In the other plots, the dye stained depth ranged from15cm to30cm. There was a log functional relationship between water infiltration rate and macropore density and an exponential functional relationship between water infiltration rate and macropore radius. There was a positive correlation between the density of macropores, water flux, and saturated hydraulic conductivity and the correlation coefficient was0.93. There was no relationship between the radius of macropores, water flux, and saturated hydraulic conductivity. Soil density showed an exponential function with steady infiltration rate and the relationship between soil porosity and steady infiltration rate can be expressed by a power function. R0.25, Soil grain composition and gravel volume content showed an inapparant correlation. Soil density and soil mechanical compositions (including volume fraction of gravel) were the main factors to affect water infiltration. Soil structure and water transport have been studied by many scholars and the research mainly focused on forest soil that has a better soil structure, but soil north rocky mountain was mentioned less. In this paper, JiFeng, north typical rocky mountain was chosen as a site where six plot were selected to analyze soil structure, water transport and the relation between them so that it can offer some relation models and theretical basic for water and soil conservation and vegetation construction.