Spatial Variation Of Soil Particle Composition And Nutrients Of Caragana Korshinskii And Stipa Bungeana On The Loess Plateau

In order to discuss the influences of different grass-shrub lands in Loess Plateau under different precipitation gradient sequences on the soil physical and chemical properties, explore the vegetation planting types with better allocation, in this article, it takes the two kinds of typical land use patterns in Loess Plateau namely the artificial Caragana korshinskii and Stipa bungeana as the example to conduct systematic research on the soil organic carbon, full nitrogen, full phosphorus, full potassium and soil mechanical compositions through the field survey in combination with in-office analysis, and comprehensively evaluates the two kinds of grass-shrub. The major conclusions are as follows:1. The overall trend of mechanical compositions of Caragana korshinskii and Stipa bungeana is presented as silt content> sand>cosmid; the distribution trend on the vertical soil profile is that the sand and cosmid contents are decreased with the increasing of soil depth, the silt and cosmid contents are increased with the decreasing of precipitation gradient; the silt has the minimal spatial variability, and cosmid has the maximum spatial variability.2. Soil fertility in Caragana korshinskii forest experiment zone is lower, all of the other nutrient contnets are at the fifth scarcity and sixth extreme sacracity levels except the full potassium at the third medium level; the organic carbon has obvious spatial variability, full nitrogen and full phosphorus belong to medium variability, full potassium belongs to weak variability; on the vertical direction, the organic carbon、full nitrogen contents are decreased with the deepening of the soil layers, which have the surface accumulation phenomenon; The full phosphorus content is presented as the decreasing from the surface to subsoil layer, the increasing from subsoil layer to the bottom; the full potassium content is presented the overall increasing trend with the increasing of soil layers; on the horizontal direction, organic carbon、full nitrogen, full phosphorus as well as the full potassium are all increased with the rising of precipitation gradient; and the the mechanical compositions of the soil and increase differences of nutrients are more obvious in regions with better precipatition conditions.3. Soil fertility in Stipa bungeana experiment zone is lower, all of the other nutrient contnets are at the fifth scarcity and sixth extreme sacracity levels except the full potassium in Fuxian County District at the third medium level; among the nutrients, organic carbon and full nitrogen have obvious spatial variability in precipitation gradient, the full phosphorus and full potassium have weaker spatial variability; on the vertical direction, the organic carbon、full nitrogen and full potassium contents will be decreased with the deepening of soil layers; the full phosphorus content is presented as decreasing from the surface to subsoil layer, increasing from the subsoil layer to the bottom layer; and on the horizontal direction, the organic carbon、full nitrogen, full phosphorus and full potassium contents are all increased with the rising of the precipitation gradient.4. In terms of the mechanical compositions of soil, Stipa bungeana in Shenmu、 Suide、Ansai precipitation zones have stronger refining capacity for soil than the Caragana korshinskii, while the conditions are on the contrary in Yanan precipitation zone; in terms of the soil nutrients, except for the organic carbon content in Shenmu district, the nutrient contents of Caragana korshinskii are all higher than those of the Stipa bungeana in the other districts, apart from the organic carbon as well as full nitrogen contents in Suide、Ansai districts and the full potassium of Stipa bungeana are higher than those of the Caragana korshinskii.5. Caragana korshinskii growing under the natural conditions in the experiment zone has slightly and limitedly better effect than Stipa bungeana in improving the soil texture in this district. In order to better improve the soil texture of Losses Plateau to larger extent, reasonable human managements shall be added at the same time of returning farmland to forests and grasslands, fertilizer and irrigation shall be timely conducted to improve the growth environment, reduce the soil and water loss in this district, so as to enhance the capacity of storing and keeping water and fertilizer of the soil.