太白山不同海拔植被带土壤矿物磁性变化规律研究

A Study on Variations in Magnetic Properties of Soils in Different Altitude-vegetation Belts on Taibai Mountain

土壤矿物磁性对环境变化具有重要的指示意义。然而,有关中国中东部东亚季风区内土壤矿物磁性随海拔高度的变化规律的研究和讨论尚不多。我们获取了太白山不同海拔高度5个典型植被带下的表土及土壤剖面样品,测量了这些样品的磁化率(χ_(lf))、频率磁化率(χ_(fd))、非磁滞剩磁(ARM)、饱和等温剩磁(SIRM)、反向磁场等温剩磁(IRM_(-300m T)),探讨了不同植被带中土壤矿物磁性特征及其变化。结果显示:(1)不同植被带下,表土矿物磁性差异显著,χ_(lf)、ARM、SIRM之间表现出良好的相关性,随海拔升高呈降低趋势,而IRM_(-300m T)/SIRM随海拔升高而升高。(2)除栓皮栎林外,其他植被带处的土壤剖面χ_(lf)、χ_(fd)、ARM、SIRM随剖面深度加深而降低,IRM_(-300m T)/SIRM随深度加深而升高;此外,低海拔的栓皮栎林与锐齿栎林处土壤剖面磁性的各个指标远高于高海拔土壤剖面磁性指标。(3)表土总体磁性矿物浓度,较细磁畴的SSD颗粒及亚铁磁性矿物浓度与不同植被带所处温度呈现正相关关系,而与其土壤中的有机质含量呈负相关,但受降雨及坡度影响较小。

IMagnetic characteristics of soils are significant to indicate environmental changes. However, studies and discussions on variations in soil magnetism with altitudes were few in the regions influenced by East Asian monsoon in central east China. We collected different samples from surface soils and soil profiles in five typical vegetation belts at different altitudes on Taibai Mountain. Furthermore, we measured magnetic susceptibility （~tf）, frequency-dependent susceptibility （Y^d%）, anhysteretic remanent magnetization （ARM）, saturation isothermal remanent magnetization （SIRM） and isothermal remanent magnetization acquired at a backfield （IRM_3oomT） for these samples. Based on these measurements, we explored soil magnetic characteristics in different vegetation belts and their variability. Results showed that：l） Magnetic characteristics of the surface soils differed distinctly in different vegetation belts. X~, ARM and SIRM had good correlations among them in the surface soils of the same vegetation belts. X~ ARM and SIRM of the surface soils decreased with the increase in altitudes, while IRM_3oomT / SIRM increased with the increase in altitudes. 2） X~, Xr~%, ARM and SIRM decreased and IRM-3oO^T / SIRM increased with depth in soil profiles at the vegetation belts except Quercus variabilis forest. In addition, the values of various magnetic parameters were much higher in the soil profiles of the Quercus variabilis forest and Quercus aliena var. aeuteserrata forest located at relatively lower altitudes than those at higher altitudes. 3） The concentrations of total magnetic minerals, relatively fine SSD gains and ferrimagnetic minerals in surface soils had positive correlations with the temperature in different vegetation belts and had negative correlations with the contents of soil organic matter. The influences of precipitation and topographical slopes were relatively small on the concentrations of magnetic minerals.