Water Availability In Stony Soil On The Loess Plateau

The Land resources is a natural product, its total amount is limited. Due to irrational development and utilization of human cause a large number of land degradation, makes it more and more concerned about how to use the limited land resources, improving land use efficiency. At this time, an important class of land resources began to be concerned about–soil contain rock fragments. In recent years, there has been a growing interest in soils containing rock fragment because researchers have realized that apart from pedogenesis reasons, a variety of human activities can lead to soil containing gravels. A large number of gravels distributions in the Loess Plateau, intensive erosion and frequent human activity led to large soil particles (gravel) upward movement and small particles (fine soil) down movement, combined with tillage erosion, wind erosion, water erosion, not only removed the surface soil small particles, but also led to loss of soil nutrients, making a large number of rock fragments exposed on the surface. Although there are a large number of researches have been conducted on rock fragments at home and broad, for the laws of water availability of soil contain rock fragments and spatial variation is still very limited. In this paper, a large number of tests had been conducted to show the rules of water availability of soil contain rock fragments and spatial variation, and did a more in-depth study on spatial distribution. The main access to the following conclusions:(1) Different soil moisture under gravel mulch with the soil depth was increases with soil depth showing a decrease after increasing. Contrast there is no gravel-covered tests and the largest volume of gravel cover (55kg) of the two tests, for the 0-20cm layer of soil, gravel-covered soil moisture content of less than there is no gravel-covered soil moisture content; and 20cm below the soil, gravel-covered soil moisture is greater than the soil is not covered by gravel. Different content there is no significant difference between the gravel cover.(2) Interlayer thickness of gravel on the soil moisture change significantly, 20cm thick gravel compartment changes in soil moisture is greater than 10cm thick insulation layer of gravel, while the 10cm thick insulation layer of gravel on the soil moisture at different locations almost the same effect. In addition, the soil compartment in the gravel impact of changes in soil moisture is greater than gravel insulation layer on the surface (for surface covering rock fragments) soil moisture changes. The existence of gravel compartment, allowing the soil moisture was "S"-shape trend which soil moisture content increased with soil depth showed increased first and then decreases, then increases and then decreases trend.(3) Soil moisture with different rock fragments content changes with the soil depth increases showed increasing trend. Dealing with fine earth soil testing soil moisture content and moisture fluctuations were significantly smaller than the gravel-containing soil test, indicating the presence of gravel increased soil moisture content.(4) Gravel coverage, the weight content of the surface 20cm soil of rock fragments, gravel size, surface roughness with "S"-type distribution in slope, that is, with increasing distance from the top of the hill, they are showing the first increase in the trend of increased and then decreased again. The distribution of coverage, content, size, and roughness not only determined by slope, but also related to the interaction between them, correlation coefficient significant at the 0.01 level. Stepwise linear regression analysis showed that the greatest impact on the stone was coverage, gravel weight distribution of its interpretation of the degree reached 52.3%, followed by slope and particle size; the greatest impact on the cover is also a stone weight, followed by the roughness and particle size; for the roughness, only the cover showing a significant impact.(5) Soil moisture at the slope on the distribution are: soil moisture, increasing from the top of the hill to the foot of the slope; surface 20cm of soil moisture above the surface 6cm of soil moisture content, large fluctuations in surface soil moisture 6cm. In the foot of the hill, does not remove the gravel surface of the surface 20cm of soil moisture high, but whether the removal of gravel for the surface layer 6cm little effect on soil moisture. Four kinds of processing spatial variability of water level variations are moderate.(6)Underground biomass of sandy soils containing gravel, formula Y = 0. 106X+77.698 could be used to correct the error when use traditional soil drilling method. Formula Y = 0. 378X+52.557 can also be used to project ground biomass and below-ground biomass relationship. This reduces the field determination of root biomass workload; provide a reference to sandy soil and Plant Physiology and Ecology Research.(7) Water availability in soil containing rock fragments increase with the increase of soil humidity no matter from leaf area, plant height, root density, or plant biomass. And there is neither apparent slow down trend when approaching field water keeping capability, nor water availability threshold point between field water keeping capacity and wilt point. In the research carrying out place, Astragalus adsurgens Pall uses more water than alfalfa does. So planting Alfalfa is helpful for the water usage in arid and semiarid area of Loess Plateau. In addition, the soil column test method of the soil water availability for the annual plants, it is proposed in the 1m tall column of soil to prevent plant roots back to long The gravel of soil by changing soil evaporation, soil infiltration, soil erosion, soil radiation, water balance and temperature characteristics to affect the earth-rock mixed soil water movement. In this paper, through different experimental design to explore the earth-rock mixed soil water movement, water availability, spatial variability patterns as well as spatial distribution of gravel, some experimental results obtained help to improve people's understanding of the soil containing gravel for improving the hydrological processes in mountainous area and the ecological restoration and environmental improvement has important significance.